Hydrogen fuel plays a critical role for the transition towards a sustainable future with utilisation in energy, chemical and other industrial sectors. Proton exchange membrane (PEM) electrolysers have been highlighted by the UK government as the most suitable technology for green hydrogen production as upon scale-up, there is a greater potential for cost reductions with increased efficiency.¹ However, PEM electrolysers employ expensive and scarce iridium oxide electrocatalysts for the oxygen evolution reaction (OER) which generates a bottleneck towards its commercialisation.² Futhermore, finding a replacement catalyst material is restricted due to the harsh operational conditions and acidic environment.³

Here we utilise automated, high-throughput (HT) synthesis, testing and characterisation methods to allow for facile screening and optimisation of potential electrocatalysts for OER in PEM electrolysis. Adam’s Fusion synthesis is performed in a Chemspeed FLEX ISYNTH and FLEX CATSCREEN to synthesise and anneal 24 catalysts in one day. In this work, we concluded a 3-fold decrease of reagent sodium nitrate achieves the same electrochemical performance compared to literature, and annealing at 450 ^oC for 1 h provides good OER performance. With XRD and TEM, we showed that these heat treatment conditions generate a catalyst with a long-range amorphous but short-range rutile crystal structure – good indications of both an active and stable OER electrocatalyst. Exploration of acid washes too has doubled the electrochemical surface area of catalyst, matching the activity of commercial iridium oxide catalysts. In turn, automated and HT electrochemical testing (DOBOT, Opentrons, multi working electrode (MWE)) are implemented to allow for seamless ink production and electrochemical assessment of materials produced. With the multi working electrode, six electrocatalysts can be tested at once compared to a tradition rotating disc electrode for facile activity screening. Moreover, initial DFT screening has highlighted potential rutile iridium mixed oxide catalysts, in which the results have been utilised towards a Bayesian optimisation campaign. Overall, this workflow allows for facile screening and optimisation of low-iridium mixed oxide catalysts, underlining active and stable OER catalysts of various compositions.

Though the work is preliminary – and focuses on the benchmarking of pure iridium oxide synthesis – it highlights advantages of automated, high-throughput workflows including speed and reliability due to lack of human involvement, screening larger syntheses spaces at once, and reduced reagent consumption, aligning with principles of green chemistry.