Hydrogen will play a key role in a low-carbon future. Although currently 95% of global hydrogen production is from the reforming of fossil fuels, it can be sustainably produced by using renewable energy sources, such as solar or wind energy, to split water molecules by electrolysis. Proton-exchange membrane (PEM) electrolysers are a mature technology, but its deployment is being held back due to lack of stable, cost-effective catalysts that are composed of non-precious metals.
Molybdenum sulphide has been shown to be a promising, precious metal-free catalyst for the hydrogen evolution reaction (HER). A former EU-funded project, PhotocatH2ode, discovered that amorphous molybdenum sulphide has a coordination polymer structure . This refined the understanding of its catalytic mechanism enabled the development of strategies to remedy reductive corrosion issues that have so far limited the implementation of this earth-abundant catalyst for HER in PEM electrolysers.
The PRODUCE-H2 project was established to optimise the composition and formulation of catalysts of the same amorphous molybdenum sulphide family. Inspired by the iron-containing nitrogenase (a H2 evolving enzyme that exists in nature) active site, ,a high performanceamorphous bimetallic iron-molybdenum sulphide catalyst has been developed and characterized. This amorphous material is produced from low-cost precursors using microwave synthesis, a method allowing for easily scalable production. This material was further formulated with proton-conducting ionomer and a nanocarbon support material, in and integrated in membrane-electrode assemblies (MEA).
The performance of the MEAs based on the earth-abundant H2-evolution material was then assessed in PEM electrolyzer. Current densities as high as 1 A/cm2 could be obtained at 80°C at the expense of 283 mV additional electrical potential compared to the benchmark platinum (Pt) catalysts – a record for non-precious metal HER catalysts. In situ accelerated stress tests revealed a very good stability (comparable to benchmark Pt) during operation. Technoeconomic and lifecycle assessment indicated a 94% lower manufacturing cost and a 2 orders of magnitude lower impact on the environment compared to platinum (on a gram-gram basis), making this a promising catalyst for future development.
