New reporting guidelines could accelerate the development of photocatalytic hydrogen production

Photocatalytic hydrogen production holds considerable promise for future industry and the transition to a sustainable energy system. However, the absence of standardised performance metrics has made it difficult to identify the most promising materials for photocatalytic hydrogen production. Researchers at Chalmers University of Technology in Sweden have now developed a new benchmarking concept that enables more reliable comparisons of photocatalyst performance.

Alexandre Holmes and Ergang Wang, the researchers behind the new reporting guidlelines for promising materials for photocatalytic hydrogen production. Photo: Hanna Magnusson and Anna-Lena Lundqvist

Hydrogen is an efficient energy carrier that can be used to store large amounts of energy over long periods. It can also be used as a fuel and as a feedstock in a range of industries, including ammonia, cement and steel manufacturers.

In fuel cells, the only by-product is water, making hydrogen an important component of the transition towards renewable energy sources. Today, however, global hydrogen production still relies predominantly on fossil fuels.

“Being able to produce hydrogen using sunlight through a process known as photocatalysis is an alternative with enormous potential. However, to translate such technology at an industrial scale, we must ensure cost-effectiveness,” says Alexandre Holmes, postdoctoral researcher in Professor Ergang Wang’s research group at the Department of Chemistry and Chemical Engineering at Chalmers University of Technology.

Difficult to choose the most effective photocatalyst

The choice of photocatalyst material has a major impact on both the efficiency and the overall cost of hydrogen production. For instance, Ergang Wang’s group is, among other things, investigating how solar hydrogen can be produced without the use of the expensive metal platinum. In a recent study, the researchers demonstrated that nanoparticles of electrically conductive plastic dispersed in water can successfully serve as photocatalysts for the reaction, without precious metals.

“There is considerable interest from industry in investing in the development of this technology, as on-site production could drastically reduce the costs. The development of photocatalyst is therefore a central part of the research. However, the central question remains: what material is the most efficient and the cheapest? Up to now, this remained a difficult question to answer. Reproducing and comparing results reported by other research groups remains a challenge due to the lack of clear guidelines in expressing photocatalytic performance,” says Alexandre Holmes.

Key parameters are not reported

At present, the criteria for evaluating the performance of materials used in photocatalytic experiments are biased across different laboratories.

“Key parameters, such as the area exposed to light, which is central in the photocatalytic process, are often not reported in scientific publications. This results in poor reproducibility and makes it difficult - if not impossible - for both researchers and industry to make informed decisions about which materials hold the most potential,” says Alexandre Holmes.

A benchmarking concept has been developed

To address this issue, the Chalmers researchers have developed a benchmarking concept consisting of clear reporting guidelines and standardised performance metrics (see fact box below).

“For a long time, we have discussed how to find a fair way to quantify photocatalyst performance. It is a difficult challenge, but also an important one. With this work, we are happy to propose a clearer benchmarking concept that can make results easier to compare and help accelerate the development of photocatalytic hydrogen production,” says Ergang Wang.

Read the scientific publication

Read the article in ACS Energy Letters: Toward Standardized and Comparable Reporting for Sacrificial Photocatalytic Hydrogen Evolution

Full transparency of experimental parameters must be ensured, allowing for clear reproduction and evaluation of performance.
The performance of photocatalysts can be compared more fairly by measuring how much hydrogen they produce in relation to both the amount of photocatalyst used and the area exposed to light.
The practical metric “solar-to-chemical conversion” indicates what percentage of the incoming light energy is converted into chemical energy stored as hydrogen.