Epitaxially Grown Bimetallic Phosphide With High Activity and Durability for Bifunctional Alkaline Anion Exchange Membrane Water Electrolysis

Abstract

Bimetallic phosphides stand promising candidates as bifunctional electrocatalysts for replacing precious noble metals on both cathode and anode in anion exchange membrane water electrolysis (AEMWE), however, the intrinsic electrochemical properties constrain their practical application. Herein, a novel hybridization approach is proposed for the facet-confined epitaxial growth of NiCoP derived on atomic defect-engineered Ti₃C₂T_x MXene (NiCoP@Ti₃C₂T_x). The efficient charge transfer across the heterointerface affects to optimizes the chemical state of the hybrid, simultaneously promoting both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. Theoretical calculations reveal that such heterostructural engineering optimizes the adsorption energy of H/O-containing intermediates for overall water splitting. The outstanding bifunctionality of NiCoP@Ti₃C₂T_x is demonstrated by requiring low overpotentials of 54 and 247 mV to reach 10 mA cm⁻² in HER and OER, respectively, and only 1.67 V to reach 100 mA cm⁻² in overall water splitting. The AEMWE cell with symmetric NiCoP@Ti₃C₂T_x configuration exhibits excellent performance of 1.96 V at 1 A cm⁻² with outstanding durability over 500 h at 0.5 A cm⁻² at 60 °C, surpassing the commercial Pt/C||RuO₂. Overall, this work shows the great potential of epitaxial growth of transition metal phosphides on defect-engineered 2D substrates to replace noble metal-based catalysts for practical AEMWE.