Ni-Co-O anodes for the alkaline oxygen evolution reaction: Multistage electrode optimization and plasma-assisted activity enhancement enabled by a coherent workflow

Abstract

Ni-Co-based oxides (Ni-Co-O) are promising oxygen evolution reaction (OER) catalysts due to their adaptable structures, affordability, abundance, and strong electrochemical performance. While various studies explored the structure-activity relationships and OER mechanisms in these catalysts, comprehensive anode development requires a systematic workflow covering all stages of catalyst optimization. Here, we present an integrated approach for characterizing commercial Ni-Co-O nanomaterials using a combination of analytics during processing, in operando, and post-catalysis to gain insights into parameters influencing anode performance. Key findings include the critical impact of catalyst ink optimization through solvent matrix screening, enabling high-quality electrode layers via ultrasonic spray coating on Ni plates. These Ni-Co-O layers, tested as anodes in alkaline OER, were further enhanced by plasma post-processing, resulting in binder-free surfaces with increased porosity and wettability compared to untreated samples. Notably, plasma treatment also promoted a more redox reversible catalyst structure, improved Fe uptake efficiency, and led to a significantly enhanced OER activity by reducing the overpotential by ~43 mV at 100 mA/cm² compared to untreated samples. Our study highlights the importance of a holistic evaluation approach, from catalyst powder to post-mortem analysis, that enabled us to discover how plasma post-processing can yield binder-free electrodes with superior electrochemical properties.