Rational design of heterostructural heterometallic phosphonates as highly efficient electrocatalysts for overall water splitting under alkaline conditions

Abstract

It is very important to design and exploit high-performance and low-cost electrocatalysts for water electrolysis to realize sustainable development. In this work, two heterostructural heterometallic phosphonates (QAU-4/QAU-2 and QAU-3/QAU-2) have been assembled via a “MOF-on-MOF” strategy and show excellent OER and HER performances under alkaline conditions. The Fe/Ni composite metal phosphonate (QAU-4/QAU-2) requires only 228 mV overpotential to realize a current density of 10 mA cm⁻² with a small Tafel slope of 41 mV dec⁻¹ for the OER; the Co/Ni composite metal phosphonate (QAU-3/QAU-2) has an overpotential of 123 mV at 10 mA cm⁻² and a Tafel slope of 81 mV dec⁻¹ for the HER. The two-electrode electrolyzer assembled from QAU-4/QAU-2 and QAU-3/QAU-2 exhibits superior performance for overall water splitting under alkaline conditions. The success of this work proves that the heterostructure and heterometal synergistic effect plays great roles in water electrolysis and provides an effective strategy for the design and optimization of high-performance water splitting electrocatalysts.