A pyrolysis-free Ni/Fe bimetallic electrocatalyst for overall water splitting

Abstract

Catalysts capable of electrochemical overall water splitting in acidic, neutral, and alkaline solution are important materials. This work develops bifunctional catalysts with single atom active sites through a pyrolysis-free route. Starting with a conjugated framework containing Fe sites, the addition of Ni atoms is used to weaken the adsorption of electrochemically generated intermediates, thus leading to more optimized energy level sand enhanced catalytic performance. The pyrolysis-free synthesis also ensured the formation of well-defined active sites within the framework structure, providing ideal platforms to understand the catalytic processes. The as-prepared catalyst exhibits efficient catalytic capability for electrochemical water splitting in both acidic and alkaline electrolytes. At a current density of 10 mA cm⁻², the overpotential for hydrogen evolution and oxygen evolution is 23/201 mV and 42/194 mV in 0.5 M H₂SO₄ and 1 M KOH, respectively. Our work not only develops a route towards efficient catalysts applicable across a wide range of pH values, it also provides a successful showcase of a model catalyst for in-depth mechanistic insight into electrochemical water splitting.

A well-defined catalyst with dual Ni/Fe atomic active sites was created using a pyrolysis-free approach. The as-made catalyst was used for overall electrochemical water splitting in both acidic and alkaline electrolytes with low overpotentials.