Rational Design of Mixed-Valence Cobalt-Based Nanowires via Simultaneous Vanadium and Iron Modulations for Enhanced Alkaline Electrochemical Water Splitting

Abstract

Strategic modulation of the electronic structure and surface chemistry of electrocatalysts is crucial for achieving highly efficient and cost-effective bifunctional catalysts for water splitting. This study demonstrates the strategic incorporation of redox-active elements (vanadium, V and iron, Fe) to optimize the catalytic interface of mixed-valence cobalt-based nanowires (Co_5.47N and CoP), which enhances hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic abilities. Experimental and theoretical analyses reveal that dual-cation doping increases the surface area and optimizes the electronic structure, which promotes rapid water dissociation, favours hydrogen adsorption kinetics, and stabilizes oxygen intermediates. Consequently, V,Fe-Co_5.47N and V,Fe-CoP nanowire electrocatalysts achieve low overpotentials of 55/251 and 63/265 mV for HER/OER at 10 mA cm^-2 in 1 M KOH electrolyte, respectively, outperforming the pristine and single-cation-doped counterparts. The alkaline overall water splitting devices assembled based on these bifunctional catalysts require only 1.64 V and 1.66 V at 100 mA cm^-2 and also demonstrates excellent durability. This work provides valuable insights into enhancing transition metal-based catalysts through redox-active element incorporation for efficient water splitting.