Once seen as fleeting, a new solar tech proves its lasting power

Princeton Engineering researchers have developed the first perovskite solar cell with a commercially viable lifetime, marking a major milestone for an emerging class of renewable energy technology. The team projects their device can perform above industry standards for around 30 years, far more than the 20 years used as a threshold for viability for solar cells.

The device is not only highly durable, it also meets common efficiency standards. It is the first of its kind to rival the performance of silicon-based cells, which have dominated the market since their introduction in 1954.

Perovskites are semiconductors with a special crystal structure that makes them well suited for solar cell technology. They can be manufactured at room temperature, using much less energy than silicon, making them cheaper and more sustainable to produce. And whereas silicon is stiff and opaque, perovskites can be made flexible and transparent, extending solar power well beyond the iconic panels that populate hillsides and rooftops across America.

But unlike silicon, perovskites are notoriously fragile. Early perovskite solar cells (PSC), created between 2009 and 2012, lasted only minutes. The projected lifetime of the new device represents a five-fold increase over the previous record, set by a lower efficiency PSC in 2017. (That device operated under continuous illumination at room temperature for one year. The new device would operate for five years under similar lab conditions.)

The Princeton team, led by Lynn Loo, the Theodora D. '78 and William H. Walton III '74 Professor in Engineering, revealed their new device and their new method for testing such devices in a paper published June 16 in Science.

Loo said the record-setting design has highlighted the durable potential of PSCs, especially as a way to push solar cell technology beyond the limits of silicon. But she also pointed past the headline result to her team's new accelerated aging technique as the work's deeper significance.

"We might have the record today," she said, "but someone else is going to come along with a better record tomorrow. The really exciting thing is that we now have a way to test these devices and know how they will perform in the long term."

Due to perovskites' well-known frailty, long-term testing hasn't been much of a concern until now. But as the devices get better and last longer, testing one design against another will become crucial in rolling out durable, consumer-friendly technologies.

"This paper is likely going to be a prototype for anyone looking to analyze performance at the intersection of efficiency and stability," said Joseph Berry, a senior fellow at the National Renewable Energy Laboratory who specializes in the physics of solar cells and who was not involved in this study. "By producing a prototype to study stability, and showing what can be extrapolated [through accelerated testing], it's doing the work everyone wants to see before we start field testing at scale. It allows you to project in a way that's really impressive."

While efficiency has accelerated at a remarkable pace over the past decade, Berry said, the stability of these devices has improved more slowly. For them to become widespread and rolled out by industry, testing will need to become more sophisticated. That's where Loo's accelerated aging process comes in.

"These kinds of tests are going to be increasingly important," Loo said. "You can make the most efficient solar cells, but it won't matter if they aren't stable."

How they got here

Early in 2020, Loo's team was working on various device architectures that would maintain relatively strong efficiency -- converting enough sunlight to electric power to make them valuable -- and survive the onslaught of heat, light and humidity that bombard a solar cell during its lifetime.

Xiaoming Zhao, a postdoctoral researcher in Loo's lab, had been working on a number of designs with colleagues. The efforts layered different materials in order to optimize light absorption while protecting the most fragile areas from exposure. They developed an ultra-thin capping layer between two crucial components: the absorbing perovskite layer and a charge-carrying layer made from cupric salt and other substances. The goal was to keep the perovskite semiconductor from burning out in a matter of weeks or months, the norm at that time.

It's hard to comprehend how thin this capping layer is. Scientists use the term 2D to describe it, meaning two dimensions, as in something that has no thickness at all. In reality, it's merely a few atoms thick -- more than a million times smaller than the smallest thing a human eye can see. While the idea of a 2D capping layer isn't new, it is still considered a promising, emerging technique. Scientists at NREL have shown that 2D layers can greatly improve long-haul performance, but no one had developed a device that pushed perovskites anywhere close to the commercial threshold of a 20-year lifetime.

Zhao and his colleagues went through scores of permutations of these designs, shifting minute details in the geometry, varying the number of layers, and trying out dozens of material combinations. Each design went into the light box, where they could irradiate the sensitive devices in relentless bright light and measure their drop in performance over time.

In the fall of that year, as the first wave of the pandemic subsided and researchers to returned to their labs to tend to their experiments in carefully coordinated shifts, Zhao noticed something odd in the data. One set of the devices still seemed to be operating near its peak efficiency.

"There was basically zero drop after nearly half a year," he said.

That's when he realized he needed a way to stress test his device faster than his real-time experiment allowed.

"The lifetime we want is about 30 years, but you can't take 30 years to test your device," Zhao said. "So we need some way to predict this lifetime within a reasonable timeframe. That's why this accelerated aging is very important."

The new testing method speeds up the aging process by illuminating the device while blasting it with heat. This process speeds up what would happen naturally over years of regular exposure. The researchers chose four aging temperatures and measured results across these four different data streams, from the baseline temperature of a typical summer day to an extreme of 230 degrees Fahrenheit, higher than the boiling point of water.

They then extrapolated from the combined data and forecast the device's performance at room temperature over tens of thousands of hours of continuous illumination. The results showed a device that would perform above 80 percent of its peak efficiency under continuous illumination for at least five years at an average temperature of 95 degrees Fahrenheit. Using standard conversion metrics, Loo said that's the lab equivalent of 30 years of outdoor operation in an area like Princeton, NJ.

Berry of NREL concurred. "It's very credible," he said. "Some people are still going to want to see it play out. But this is much more credible science than a lot of other attempts at forecasting."

The Michael Jordan of solar cells

Perovskite solar cells were pioneered in 2006, with the first published devices following in 2009. Some of the earliest devices lasted only seconds. Others minutes. In the 2010s the device lifetimes grew to days and weeks and finally months. Then in 2017, a group from Switzerland published a groundbreaking paper on a PSC that lasted for one full year of continuous illumination.

Meanwhile, the efficiency of these devices has skyrocketed over the same period. While the first PSC showed a power-conversion efficiency of less than 4 percent, researchers boosted that metric nearly tenfold in as many years. It was the fastest improvement scientists had seen in any class of renewable-energy technology to date.

So why the push for perovskites? Berry said a combination of recent advances make them uniquely desirable: newly high efficiencies, an extraordinary "tunability" that allows scientists to make highly specific applications, the ability to manufacture them locally with low energy inputs, and now a credible forecast of extended life coupled with a sophisticated aging process to test a wide array of designs.

Loo said it's not that PSCs will replace silicon devices so much that the new technology will complement the old, making solar panels even cheaper, more efficient and more durable than they are now, and expanding solar energy into untold new areas of modern life. For example, her group recently demonstrated a completely transparent perovskite film (having different chemistry) that can turn windows into energy producing devices without changing their appearance. Other groups have found ways to print photovoltaic inks using perovskites, allowing formfactors scientists are only now dreaming up.

But the main advantage in the long run, according to both Berry and Loo: Perovskites can be manufactured at room temperature, whereas silicon is forged at around 3000 degrees Fahrenheit. That energy has to come from somewhere, and at the moment that means burning a lot of fossil fuels.

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An anode-free zinc battery that could someday store renewable energy

 Renewable energy sources, such as wind and solar power, could help decrease the world's reliance on fossil fuels. But first, power companies need a safe, cost-effective way to store the energy for later use. Massive lithium-ion batteries can do the job, but they suffer from safety issues and limited lithium availability. Now, researchers reporting in ACS' Nano Letters have made a prototype of an anode-free, zinc-based battery that uses low-cost, naturally abundant materials.

Aqueous zinc-based batteries have been previously explored for grid-scale energy storage because of their safety and high energy density. In addition, the materials used to make them are naturally abundant. However, the rechargeable zinc batteries developed so far have required thick zinc metal anodes, which contain a large excess of zinc that increases cost. Also, the anodes are prone to forming dendrites -- crystalline projections of zinc metal that deposit on the anode during charging -- that can short-circuit the battery. Yunpei Zhu, Yi Cui and Husam Alshareef wondered whether a zinc anode was truly needed. Drawing inspiration from previous explorations of "anode-free" lithium and sodium-metal batteries, the researchers decided to make a battery in which a zinc-rich cathode is the sole source for zinc plating onto a copper current collector.

In their battery, the researchers used a manganese dioxide cathode that they pre-intercalated with zinc ions, an aqueous zinc trifluoromethanesulfonate electrolyte solution and a copper foil current collector. During charging, zinc metal gets plated onto the copper foil, and during discharging the metal is stripped off, releasing electrons that power the battery. To prevent dendrites from forming, the researchers coated the copper current collector with a layer of carbon nanodiscs. This layer promoted uniform zinc plating, thereby preventing dendrites, and increased the efficiency of zinc plating and stripping. The battery showed high efficiency, energy density and stability, retaining 62.8% of its storage capacity after 80 charging and discharging cycles. The anode-free battery design opens new directions for using aqueous zinc-based batteries in energy storage systems, the researchers say.

From Science Daily

Carbon capture: Faster, greener way of producing carbon spheres

 A fast, green and one-step method for producing porous carbon spheres, which are a vital component for carbon capture technology and for new ways of storing renewable energy, has been developed by Swansea University researchers.

The method produces spheres that have good capacity for carbon capture, and it works effectively at a large scale.

Carbon spheres range in size from nanometers to micrometers. Over the past decade they have begun to play an important role in areas such as energy storage and conversion, catalysis, gas adsorption and storage, drug and enzyme delivery, and water treatment.

They are also at the heart of carbon capture technology, which locks up carbon rather than emitting it into the atmosphere, thereby helping to tackle climate change.

The problem is that existing methods of making carbon spheres have drawbacks. They can be expensive or impractical, or they produce spheres that perform poorly in capturing carbon. Some use biomass, making them more environmentally friendly, but they require a chemical to activate them.

This is where the work of the Swansea team, based in the University's Energy Safety Research Institute, represents a major advance. It points the way towards a better, cleaner and greener way of producing carbon spheres.

The team adapted an existing method known as CVD -- chemical vapour deposition. This involves using heat to apply a coating to a material. Using pyromellitic acid as both carbon and oxygen source, they applied the CVD method at different temperatures, from 600-900 °C. They then studied how efficiently the spheres were capturing CO2 at different pressures and temperatures

They found that:
 

• 800 °C was the optimum temperature for forming carbon spheres
• The ultramicropores in the spheres that were produced gave them a high carbon capture capacity at both atmospheric and lower pressures
• Specific surface area and total pore volume were influenced by the deposition temperature, leading to an appreciable change in overall carbon dioxide capture capacity
• At atmospheric pressure the highest CO2 adsorption capacities, measured in millimolars per gram, for the best carbon spheres, were around 4.0 at 0 °C and 2.9 at 25 °C.

This new approach brings several advantages over existing methods of producing carbon spheres. It is alkali-free and it doesn't need a catalyst to trigger the shaping of the spheres. It uses a cheap and safe feedstock which is readily available in the market. There is no need for solvents to purify the material. It is also a rapid and safe procedure.

Dr Saeid Khodabakhshi of the Energy Safety Research Institute at Swansea University, who led the research, said:

"Carbon spheres are fast becoming vital products for a green and sustainable future. Our research shows a green and sustainable way of making them.

We demonstrated a safe, clean and rapid way of producing the spheres. Crucially, the micropores in our spheres means they perform very well in capturing carbon. Unlike other CVD methods, our procedure can produce spheres at large scale without relying on hazardous gas and liquid feedstocks.

Read more at Science Daily

New solar panel design could lead to wider use of renewable energy

 Designing solar panels in checkerboard lines increases their ability to absorb light by 125 per cent, a new study says.

Researchers say the breakthrough could lead to the production of thinner, lighter and more flexible solar panels that could be used to power more homes and be used in a wider range of products.

The study -- led by researchers from the University of York and conducted in partnership with NOVA University of Lisbon (CENIMAT-i3N) -- investigated how different surface designs impacted on the absorption of sunlight in solar cells, which put together form solar panels.

Scientists found that the checkerboard design improved diffraction, which enhanced the probability of light being absorbed which is then used to create electricity.

The renewable energy sector is constantly looking for new ways to boost the light absorption of solar cells in lightweight materials that can be used in products from roof tiles to boat sails and camping equipment.

Solar grade silicon -- used to create solar cells -- is very energy intensive to produce, so creating slimmer cells and changing the surface design would make them cheaper and more environmentally friendly.

Dr Christian Schuster from the Department of Physics said: "We found a simple trick for boosting the absorption of slim solar cells. Our investigations show that our idea actually rivals the absorption enhancement of more sophisticated designs -- while also absorbing more light deep in the plane and less light near the surface structure itself.

"Our design rule meets all relevant aspects of light-trapping for solar cells, clearing the way for simple, practical, and yet outstanding diffractive structures, with a potential impact beyond photonic applications.

"This design offers potential to further integrate solar cells into thinner, flexible materials and therefore create more opportunity to use solar power in more products."

The study suggests the design principle could impact not only in the solar cell or LED sector but also in applications such as acoustic noise shields, wind break panels, anti-skid surfaces, biosensing applications and atomic cooling.

Dr Schuster added: "In principle, we would deploy ten times more solar power with the same amount of absorber material: ten times thinner solar cells could enable a rapid expansion of photovoltaics, increase solar electricity production, and greatly reduce our carbon footprint.

"In fact, as refining the silicon raw material is such an energy-intensive process, ten times thinner silicon cells would not only reduce the need for refineries but also cost less, hence empowering our transition to a greener economy."

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Splitting water molecules for a renewable energy future

 The future economy based on renewable and sustainable energy sources might utilize battery-powered cars, large-scale solar and wind farms, and energy reserves stored in batteries and chemical fuels. Although there are examples of sustainable energy sources in use already, scientific and engineering breakthroughs will determine the timeline for widespread adoption.

One proposed paradigm for shifting away from fossil fuels is the hydrogen economy, in which hydrogen gas powers society's electrical needs. To mass produce hydrogen gas, some scientists are studying the process of splitting water -- two hydrogen atoms and one oxygen atom -- which would result in hydrogen fuel and breathable oxygen gas.

Feng Lin, an assistant professor of chemistry in the Virginia Tech College of Science, is focusing on energy storage and conversion research. This work is part of a new study published in the journal Nature Catalysis that solves a key, fundamental barrier in the electrochemical water splitting process where the Lin Lab demonstrates a new technique to reassemble, revivify, and reuse a catalyst that allows for energy-efficient water splitting. Chunguang Kuai, a former graduate student of Lin's, is first author of the study with Lin and co-authors chemistry graduate students Zhengrui Xu, Anyang Hu, and Zhijie Yang.

The core idea of this study goes back to a subject in general chemistry classes: catalysts. These substances increase the rate of a reaction without being consumed in the chemical process. One way a catalyst increases the reaction rate is by decreasing the amount of energy needed for the reaction to commence.

Water may seem basic as a molecule made up of just three atoms, but the process of splitting it is quite difficult. But Lin's lab has done so. Even moving one electron from a stable atom can be energy-intensive, but this reaction requires the transfer of four to oxidize oxygen to produce oxygen gas.

"In an electrochemical cell, the four-electron transfer process will make the reaction quite sluggish, and we need to have a higher electrochemical level to make it happen," Lin said. "With a higher energy needed to split water, the long-term efficiency and catalyst stability become key challenges."

In order to meet that high energy requirement, the Lin Lab introduces a common catalyst called mixed nickel iron hydroxide (MNF) to lower the threshold. Water splitting reactions with MNF work well, but due to the high reactivity of MNF, it has a short lifespan and the catalytic performance decreases quickly.

Lin and his team discovered a new technique that would allow for periodic reassembling to MNF's original state, thus allowing the process of splitting water to continue. (The team used fresh water in their experiments, but Lin suggests salt water -- the most abundant form of water on Earth -- could work as well.)

MNF has a long history with energy studies. When Thomas Edison tinkered with batteries more than a century ago, he also used the same nickel and iron elements in nickel hydroxide-based batteries. Edison observed the formation of oxygen gas in his nickel hydroxide experiments, which is bad for a battery, but in the case of splitting water, production of oxygen gas is the goal.

"Scientists have realized for a long time that the addition of iron into the nickel hydroxide lattice is the key for the reactivity enhancement of water splitting." Kuai said. "But under the catalytic conditions, the structure of the pre-designed MNF is highly dynamic due to the highly corrosive environment of the electrolytic solution."

During Lin's experiments, MNF degrades from a solid form into metal ions in the electrolytic solution -- a key limitation to this process. But Lin's team observed that when the electrochemical cell flips from the high, electrocatalytic potential to a low, reducing potential, just for a period of two minutes, the dissolved metal ions reassemble into the ideal MNF catalyst. This occurs due to a reversal of the pH gradient within the interface between the catalyst and the electrolytic solution.

"During the low potential for two minutes, we demonstrated we not only get nickel and iron ions deposited back into the electrode, but mixing them very well together and creating highly active catalytic sites," Lin said. "This is truly exciting, because we rebuild the catalytic materials at the atomic length scale within a few nano-meter electrochemical interface."

Another reason that the reformation works so well is that the Lin Lab synthesized novel MNF as thin sheets that are easier to reassemble than a bulk material.

Validating findings through X-rays

To corroborate these findings, Lin's team conducted synchrotron X-ray measurements at the Advanced Photon Source of Argonne National Laboratory and at Stanford Synchrotron Radiation Lightsource of SLAC National Accelerator Laboratory. These measurements use the same basic premise as the common hospital X-ray but on a much larger scale.

"We wanted to observe what had happened during this entire process," Kuai said. "We can use X-ray imaging to literally see the dissolution and redeposition of these metal irons to provide a fundamental picture of the chemical reactions."

Synchrotron facilities require a massive loop, similar to the size of the Drillfield at Virginia Tech, that can perform X-ray spectroscopy and imaging at high speeds. This provides Lin high levels of data under the catalytic operating conditions. The study also provides insights into a range of other important electrochemical energy sciences, such as nitrogen reduction, carbon dioxide reduction, and zinc-air batteries.

"Beyond imaging, numerous X-ray spectroscopic measurements have allowed us to study how individual metal ions come together and form clusters with different chemical compositions," Lin said. "This has really opened the door for probing electrochemical reactions in real chemical reaction environments."

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Water vapor in the atmosphere may be prime renewable energy source

The search for renewable energy sources, which include wind, solar, hydroelectric dams, geothermal, and biomass, has preoccupied scientists and policymakers alike, due to their enormous potential in the fight against climate change. A new Tel Aviv University study finds that water vapor in the atmosphere may serve as a potential renewable energy source in the future.

The research, led by Prof. Colin Price in collaboration with Prof. Hadas Saaroni and doctoral student Judi Lax, all of TAU's Porter School of the Environment and Earth Sciences, is based on the discovery that electricity materializes in the interaction between water molecules and metal surfaces. It was published in Scientific Reports on May 6, 2020.

"We sought to capitalize on a naturally occurring phenomenon: electricity from water," explains Prof. Price. "Electricity in thunderstorms is generated only by water in its different phases -- water vapor, water droplets, and ice. Twenty minutes of cloud development is how we get from water droplets to huge electric discharges -- lightning -- some half a mile in length."

The researchers set out to try to produce a tiny low-voltage battery that utilizes only humidity in the air, building on the findings of earlier discoveries. In the nineteenth century, for example, English physicist Michael Faraday discovered that water droplets could charge metal surfaces due to friction between the two. A much more recent study showed that certain metals spontaneously build up an electrical charge when exposed to humidity.

The scientists conducted a laboratory experiment to determine the voltage between two different metals exposed to high relative humidity, while one is grounded. "We found that there was no voltage between them when the air was dry," Prof. Price explains. "But once the relative humidity rose above 60%, a voltage began to develop between the two isolated metal surfaces. When we lowered the humidity level to below 60%, the voltage disappeared. When we carried out the experiment outside in natural conditions, we saw the same results.

"Water is a very special molecule. During molecular collisions, it can transfer an electrical charge from one molecule to the other. Through friction, it can build up a kind of static electricity," says Prof. Price. "We tried to reproduce electricity in the lab and found that different isolated metal surfaces will build up different amounts of charge from water vapor in the atmosphere, but only if the air relative humidity is above 60%. This occurs nearly every day in the summer in Israel and every day in most tropical countries."

According to Prof. Price, this study challenges established ideas about humidity and its potential as an energy source. "People know that dry air results in static electricity and you sometimes get 'shocks' you when you touch a metal door handle. Water is normally thought of as a good conductor of electricity, not something that can build up charge on a surface. However, it seems that things are different once the relative humidity exceeds a certain threshold," he says.

The researchers, however, showed that humid air may be a source of charging surfaces to voltages of around one volt. "If a AA battery is 1.5V, there may be a practical application in the future: to develop batteries that can be charged from water vapor in the air," Prof. Price adds.

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Water splitting advance holds promise for affordable renewable energy

Model water molecules illustration.

A breakthrough into splitting water into its parts could help make renewable energy pay off, even when the sun isn't shining and the wind isn't blowing.

Using solar and wind power when it is available for water splitting, a process that uses electricity to split H2O into hydrogen and oxygen, offers a way to store energy in the form of hydrogen fuel.

Currently the most popular system used for water splitting, or water electrolysis, relies on precious metals as catalysts, but a collaborative research team, including scientists from Los Alamos National Laboratory and Washington State University, has developed a system that uses less expensive and more abundant materials. They describe the advance in a paper published in Nature Energy on March 9.

"The current water electrolysis system uses a very expensive catalyst. In our system, we use a nickel-iron based catalyst, which is much cheaper, but the performance is comparable," said Yu Seung Kim, a research scientist at Los Alamos National Laboratory and corresponding author on the paper.

Most water splitting today is conducted using a piece of equipment called a proton exchange membrane water electrolyzer, which generates hydrogen at a high production rate. It's expensive, and works under very acidic conditions, requiring precious metal catalysts such as platinum and iridium as well as corrosion-resistant metal plates made of titanium.

The research team worked to solve this problem by splitting water under alkaline, or basic, conditions with an anion exchange membrane electrolyzer. This type of electolyzer does not need a catalyst based on precious metals. In fact, a team led by Yuehe Lin, professor at WSU's School of Mechanical and Materials Engineering, created a catalyst based on nickel and iron, elements that are less expensive and more abundant in the environment.

Lin's team shared their development with Kim at Los Alamos, whose team in turn developed the electrode binder to use with the catalyst. The electrode binder is a hydroxide conducting polymer that binds catalysts and provides a high pH environment for fast electrochemical reactions.

The combination of the Los Alamos-developed electrode binder and WSU's catalyst boosted the hydrogen production rate to nearly ten times the rate of previous anion exchange membrane electrolyzers, making it comparable with the more expensive proton exchange membrane electrolyzer.

About 10 million metric tons of hydrogen are currently produced in the United States every year, mostly by using natural gas in a process called natural gas reforming, according to the U.S. Department of Energy. Hydrogen produced from a water splitting process that is powered by electricity from renewable energy holds many economic and environmental benefits, Lin said.

"Water splitting is a clean technology, but you need electricity to do it," said Lin, who is also a corresponding author on the paper. "Now we have a lot of renewable energy, wind and solar power, but it is intermittent. For example, at night we can't use solar, but if during the day, we can use extra energy to convert it into something else, like hydrogen, that's very promising."

The global hydrogen generation market is expected reach $199.1 billion by 2023. Potential markets for hydrogen energy include everything from mass energy conversion and power grid management to fuel cells for cars. Lin estimates that there are approximately 600 wind farms in the United States ready for direct connections to water electrolysis systems.

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World's fastest hydrogen sensor could pave the way for clean hydrogen energy

Fast and accurate sensors will be crucial in a sustainable society where hydrogen is an energy carrier. Hydrogen gas is produced by water that is split with the help of electricity from wind power or solar energy. The sensors are needed both when the hydrogen is produced and when it is used, for example in cars powered by a fuel cell. In order to avoid the formation of flammable and explosive gas when hydrogen is mixed with air, the hydrogen sensors need to be able to quickly detect leaks.

Hydrogen is a clean and renewable energy carrier that can power vehicles, with water as the only emission. Unfortunately, hydrogen gas is highly flammable when mixed with air, so very efficient and effective sensors are needed. Now, researchers from Chalmers University of Technology, Sweden, present the first hydrogen sensors ever to meet the future performance targets for use in hydrogen powered vehicles.

The researchers' ground-breaking results were recently published in the scientific journal Nature Materials. The discovery is an optical nanosensor encapsulated in a plastic material. The sensor works based on an optical phenomenon -- a plasmon -- which occurs when metal nanoparticles are illuminated and capture visible light. The sensor simply changes colour when the amount of hydrogen in the environment changes.

The plastic around the tiny sensor is not just for protection, but functions as a key component. It increases the sensor's response time by accelerating the uptake of the hydrogen gas molecules into the metal particles where they can be detected. At the same time, the plastic acts as an effective barrier to the environment, preventing any other molecules from entering and deactivating the sensor. The sensor can therefore work both highly efficiently and undisturbed, enabling it to meet the rigorous demands of the automotive industry -- to be capable of detecting 0.1 percent hydrogen in the air in less than a second.

"We have not only developed the world's fastest hydrogen sensor, but also a sensor that is stable over time and does not deactivate. Unlike today's hydrogen sensors, our solution does not need to be recalibrated as often, as it is protected by the plastic," says Ferry Nugroho, a researcher at the Department of Physics at Chalmers.

It was during his time as a PhD student that Ferry Nugroho and his supervisor Christoph Langhammer realised that they were on to something big. After reading a scientific article stating that no one had yet succeeded in achieving the strict response time requirements imposed on hydrogen sensors for future hydrogen cars, they tested their own sensor. They realised that they were only one second from the target -- without even trying to optimise it. The plastic, originally intended primarily as a barrier, did the job better than they could have imagined, by also making the sensor faster. The discovery led to an intense period of experimental and theoretical work.

"In that situation, there was no stopping us. We wanted to find the ultimate combination of nanoparticles and plastic, understand how they worked together and what made it so fast. Our hard work yielded results. Within just a few months, we achieved the required response time as well as the basic theoretical understanding of what facilitates it," says Ferry Nugroho.

Detecting hydrogen is challenging in many ways. The gas is invisible and odourless, but volatile and extremely flammable. It requires only four percent hydrogen in the air to produce oxyhydrogen gas, sometimes known as knallgas, which ignites at the smallest spark. In order for hydrogen cars and the associated infrastructure of the future to be sufficiently safe, it must therefore be possible to detect extremely small amounts of hydrogen in the air. The sensors need to be quick enough that leaks can be rapidly detected before a fire occurs.

"It feels great to be presenting a sensor that can hopefully be a part of a major breakthrough for hydrogen-powered vehicles. The interest we see in the fuel cell industry is inspiring," says Christoph Langhammer, Professor at Chalmers Department of Physics.

Although the aim is primarily to use hydrogen as an energy carrier, the sensor also presents other possibilities. Highly efficient hydrogen sensors are needed in the electricity network industry, the chemical and nuclear power industry, and can also help improve medical diagnostics.

"The amount of hydrogen gas in our breath can provide answers to, for example, inflammations and food intolerances. We hope that our results can be used on a broad front. This is so much more than a scientific publication," says Christoph Langhammer.

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