Bimetallic Cobalt-Vanadium Boride as a Bifunctional Electrocatalyst for Overall Water Splitting

Abstract

The transition to a hydrogen-based economy necessitates the development of sustainable and cost-effective electrocatalysts for green hydrogen production via water electrolysis. In this study, we report a novel cobalt-vanadium boride (CoVB) catalyst, which exhibits enhanced bifunctional activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. CoVB was synthesized using a facile one-step chemical reduction method with varying vanadium concentrations, optimizing performance at a 3% vanadium content. Electrochemical analyses demonstrated that CoVB significantly outperformed cobalt boride (CoB), achieving an HER and OER overpotential (η₁₀) of 80 mV and 320 mV, respectively, comparable to noble metal benchmarks. Characterization results revealed that V plays a promoting role in inhibiting the growth of particles and agglomeration of particles, leading to an increase in surface area and producing unique mixed amorphous and crystalline structures in CoVB to enhance catalytic activity by increasing the number of active sites and conductivity across the interface. Furthermore, in two-electrode systems, the cell voltage of 1.66 V was needed to achieve 10 mA/cm² of current density with superior stability and reusability. Overall, the CoVB catalyst, a new candidate from the metal boride family, presents a promising alternative to precious metals for efficient and sustainable water-splitting in alkaline electrolyzers.

Graphical Abstract