Mixed-valent cobalt phosphate/borophene nanohybrids for efficient electrocatalytic oxygen evolution reaction

Abstract

Developing efficient, low-cost, non-precious, and stable electrocatalysts is necessary for sustainable electrocatalytic water splitting. Recently, borophene has emerged as a novel two-dimensional material with exciting properties. Although several researchers have theoretically predicted its applicability towards effective electrocatalytic water splitting, studies on its practical applications are still limited. In this regard, a mixed-valent cobalt phosphate/borophene nanohybrid (BCoPi) was synthesized using the hydrothermal method, and its activity towards oxygen evolution reaction (OER) was systematically studied. The electron-deficient nature of borophene enables the activation of catalytic sites and facilitates electron transport owing to its highly conductive nature. It can act as a proton acceptor along with phosphate groups, as well as provide multiple secondary active sites in addition to Co, breaking the scaling relation of OER. For BCoPi, achieving a current density of 50 mA cm -2, 100 mA cm- 2 and 500 mA cm -2 requires an overpotential of 337 mV, 357 mV, and 401 mV, respectively, in an alkaline medium, which is superior to pristine cobalt phosphate (CoPi). It also exhibits a low Tafel slope of 61.81 mV dec- 1, suggesting faster OER kinetics and excellent long-term stability. This study will extend the development and application of borophene-based heterostructures for highly active and stable electrocatalysts for various applications.