Development of Unsupported Ru and Ni Based Oxides with Enhanced Performance for the Oxygen Evolution Reaction in Acidic Media

Abstract

The high cost of catalyst materials suitable for the oxygen evolution reaction (OER) in polymer electrolyte membrane water electrolyzers (PEMWE) is still a major hurdle that needs overcoming before commercial PEMWE can have a meaningful impact as a technology in the hydrogen economy. Metal oxides based on precious metals are currently still the most reliable and most used materials as catalysts in PEMWE; however, alternative or modified materials are desirable to help reduce the cost associated with the catalyst component. In this study, we report on binary metal oxide catalysts based on Ru and Ni. Ni-based electrodes are typically used in alkaline water electrolyzers due to their high performance, robustness and low cost; however, Ni and NiO electrodes do not show promising performance in acidic environments due to corrosion. By combining NiO with acid stable RuO₂, we have demonstrated that the performance of the RuO₂ catalyst can be improved and due to the lower cost of Ni, the cost of the catalyst can ultimately be reduced. The Ni addition was limited to 10 mol% to achieve improved OER performance followed by noticeable performance degradation as the Ni composition was increased. The metal oxide catalysts were synthesized via a modified Adams fusion method that produced nano-sized catalysts with superior performance compared to a state-of-art commercial RuO₂ catalyst. Physical characterizations were performed via high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray, and Brunauer Emmett Teller analyses. OER performances were evaluated via cyclic voltammetry, linear sweep voltammetry, chronopotentiometry, and chronoamperometry analyses.

Graphical Abstract