Achieving superior oxygen evolution performance on multi-cation boride catalysts

Abstract

Finding electrocatalysts with both ultra-low overpotential onsets and Tafel slopes is the ultimate goal for largely reducing the electricity input for generating green hydrogen energy. Here, we report the finding of a high-performance oxygen evolution reaction (OER) catalyst (FeCoNi)B among several medium/high-entropy metal borides, which is superior to hundreds of OER catalysts studied so far. Our density functional theory calculations of the surface d-band centers of the boride catalysts revealed a “volcano”-type plot with (FeCoNi)B located at the summit, confirming its excellent OER performance. The presence of different d-band centers in the multi-cations supports our idea of spontaneous adoption of a shifting catalyzing center by the catalyst for maximizing its OER activity. This is validated by adsorption energy calculations on a hydroxylated surface. The OER rate-determining step was determined to be the second elementary reaction, suggesting subsequent preferential desorption of oxygen-containing intermediates from cations with relatively low d-band centers. This work pioneers a novel concept of shifting catalytic centers in medium-/high-entropy catalysts and demonstrates a promising method to achieve significant catalytic performance through d-band center modulation.