P-doped CoCu aerogel as a bifunctional electrocatalyst for efficient overall water splitting

Abstract

The exploration of bifunctional transition metal-based catalysts for water electrolysis is important for clean and large-scale production of hydrogen but yet remains challenging. Herein, a novel phosphorous doped cobalt-copper aerogel (P-CoCu) with three-dimensional interconnected structure was prepared via spontaneous gelation and in-situ P doping process. The electronic structure and charge density of Co could be modulated upon alloying with Cu, resulting in optimized charge transfer efficiency and proton adsorption energy. The hydrophilicity and the bond strength of H* were further optimized through P doping, which promoted the reaction efficiency on the surface of P-CoCu. Besides, the unique porous morphology of aerogel endowed the catalyst with efficient mass transfer pathways and abundant active sites. Density functional theory (DFT) calculations further revealed the electron redistribution and the optimization of H2 desorption performance through Cu alloying and P doping. Based on the outstanding features, the optimized P-CoCu sample achieved extremely low overpotentials of 74/224 mV for hydrogen evolution reaction (HER) / oxygen evolution reaction (OER) at a current density of 10 mA·cm−2 in 1 M KOH electrolyte. Additionally, a two-electrode electrolytic cell assembled with P-CoCu only required an operating voltage of 1.57 V at 10 mA·cm−2 with decent stability, which was comparable to commercial noble-metal catalysts (Pt/C//RuO2/C) and superior to recently published electrocatalyst. This work provides an anticipated perspective of non-noble metal-based bifunctional catalysts for overall water splitting.