Going from Pt to PGM-free Catalysts: Effects of Ink Compositions on PEM Water Electrolysis

Abstract

The commercialisation of PEM water electrolysis is still hindered by the necessity of using noble metals that are rare, expensive and therefore unsustainable. To replace the benchmark HER catalyst Pt with more abundant materials, promising non-noble catalysts need to be identified and optimal electrode preparation and electrolysis conditions need to be transferred between catalyst materials to reveal their full potential under industrially relevant conditions. This study investigates the optimal ink composition for spray-coating the cathode regarding the effects on electrode structure, performance and catalyst layer composition. The ratio of catalyst to binder and carbon support was varied as well as the specific carbon material and the resulting electrodes were analysed via polarisation curves, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy for three different catalysts. These results show that ink compositions with a catalyst : carbon : binder ratio of 3 : 1 : 1 using Carbon Vulcan give the highest performance. Interestingly, resulting trends concerning electrochemical behaviour and electrode structure observed with different characterisation techniques can be transferred between Pt catalysts and non-noble transition metal chalcogenide materials. Boosting the performance via ink optimisation is much more pronounced for the non-noble catalysts, narrowing the gap to competing with noble standard Pt materials.