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 demonstrated 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 enhanced their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activity. Experimental and theoretical analyses revealed that the dual-cation doping increased the surface area and optimized the electronic structure of the nanowires, which promoted rapid water dissociation, favoured hydrogen adsorption kinetics, and stabilized the oxygen intermediates. Consequently, the V,Fe-Co_5.47N and V,Fe-CoP nanowire electrocatalysts achieved low overpotentials of 55/251 and 63/265 mV for HER/OER at 10 mA cm⁻² in 1 M KOH electrolyte, respectively, outperforming their pristine and single-cation-doped counterparts. The alkaline overall water-splitting devices assembled based on these bifunctional catalysts required an overall voltage of only 1.64 V and 1.66 V at 100 mA cm⁻² and also demonstrated excellent durability. This work provides valuable insights into enhancing transition metal-based catalysts through the incorporation of redox-active elements for efficient water splitting.