Rational design and construction of hierarchical porous quasi-hexagonal Co2P nanosheets/Co heterostructures as highly efficient bifunctional electrocatalysts for overall water splitting

Abstract

Constructing heterostructured electrocatalysts has proven effective in enhancing intrinsic catalytic activity. Herein, under guidance of theoretical calculations, hierarchical porous quasi-hexagonal Co₂P nanosheets/Co heterostructures supported on carbon cloth (Co₂P/Co/CC) with a high surface area were rationally designed and elaborately constructed through electroless Co plating, electrochemical oxidation, and phosphidation process, which showed significant electrocatalytic performance toward water electrolysis. Specifically, theoretical calculations revealed that the Co₂P/Co heterostructure adjusted the electronic structure of Co₂P and Co, reducing the energy barrier for target reactions and thereby boosting electrocatalytic activities for the hydrogen evolution reaction (HER). Notably, the typical Co₂P/Co/CC catalyst demonstrated impressive HER performance, with low overpotentials of only 52 and 48 mV to achieve a current density of 10 mA/cm² in 0.5 M H₂SO₄ and 1.0 M KOH solutions, respectively. The remarkable electrocatalytic performance of the catalyst can be attributed to the improved intrinsic activity resulting from the Co₂P/Co heterostructures and the highly exposed active sites provided by the hierarchical porous structures. Furthermore, the Co₂P/Co/CC catalyst exhibited excellent oxygen evolution reaction (OER) performance in alkaline electrolyte, requiring a low overpotential of only 306 mV to achieve a current density of 100 mA/cm². Additionally, a two-electrode electrolyzer assembled with the Co₂P/Co/CC electrodes achieved a current density of 10 mA/cm² at a low cell voltage of 1.54 V and demonstrated excellent long-term stability. This work presents a novel and feasible strategy for constructing hierarchical heterostructured electrocatalysts that enable efficient water electrolysis. By combining rational design and theoretical guidance, our approach offers promising prospects for advancing the field of electrocatalysis and facilitating sustainable energy conversion.

Keywords: Bifunctional electrocatalyst; Co(2)P/Co heterostructures; Cobalt phosphide; Porous quasi-hexagonal nanosheets; Water splitting.