Proceedings of MATSUS Fall 2024 Conference (MATSUSFall24)
Publication date: 28th August 2024
A major challenge to commercialization of the alkaline electrolyzer technology is the development of efficient, cheap and non-precious catalysts for oxygen evolution reaction (OER),occurring at the anode of an electrolyzer. Nickel borides are potential candidates due to their bifunctionality, abundance and ease of large-scale synthesis[1]. Though there were several studies reporting the OER activity of Ni2B and Ni3B compounds, they were performed on powder samples with rotating disk electrodes where ensemble effects and presence of binders could hinder the direct structure/composition-activity correlation[1–3].
In this study, scanning electrochemical cell microscopy (SECCM)[4] is employed to evaluate the intrinsic OER activity of Ni2B and Ni3B phases homogeneously distributed within the specimen with nominal composition Ni70B30 synthesized via arc melting. SECCM allows to perform a series of localized electrochemical measurements directly on Ni70B30 surface of sizes defined by a mobile electrochemical cell formed by the electrolyte-filled nanopipette probe[5]. The obtained OER activity map of Ni70B30 surface from SECCM closely correlates to the phase distribution in the two-phase sample, revealing higher activity of Ni3B compared to Ni2B. Interestingly, the OER currents recorded on Ni2B and Ni3B are influenced by the gaseous environment (air, Ar, CO2 and O2) surrounding the electrolyte droplet (SECCM probe). Notably, in the presence of 2% CO2, the overall current density decreased while the measurements in Ar environment showed the highest OER activity with the current density at 1.8 V vs. RHE being 18.7 ± 0.4 mA cm-2 and 25.2 ± 0.7 mA cm-2 for Ni2B and Ni3B respectively.
The authors acknowledge the financial support from BMBF via the project PrometH2eus (03HY105F).