Intermolecular electron modulation by P/O bridging in an IrO2-CoPi catalyst to enhance the hydrogen evolution reaction

Abstract

Development of a highly efficient electrocatalyst for the hydrogen evolution reaction (HER) remains a great challenge. Herein, a catalytic system is constructed based on a low content of atomically dispersed iridium oxide (IrO₂) coordinated with cobalt phosphate (CoPi) onto carbon nanotubes (CNTs) by a two-step electrochemical deposition procedure. The resultant IrO₂-CoPi-CNT catalytic system with a low loading of Ir (0.41 wt%) has Pt-like performances with a small overpotential of 29 mV at a current density of 10 mA cm⁻² and a low Tafel slope of 27 mV dec⁻¹ towards the HER. X-ray photoelectron spectroscopy (XPS) measurements and density functional theory (DFT) calculations reveal that the electronic structure of CoPi and IrO₂ can be effectively modulated through electron-donating phosphate bonds (P/O bridging),thus giving a more favorable ΔG_H* with a value of −0.13 eV. These bonds also prevent IrO₂ from undergoing further aggregation. Besides, CoPi can rapidly cleave HO–H bonds and transfer an abundance of H* intermediates to nearby IrO₂ catalytic sites, facilitating the formation and release of H₂ molecules. This work manifests the importance of the electron structure of catalysts in electrocatalysis and provides an avenue for preparing highly active electrocatalysts towards the HER.