CeO₂-Modified Ni₂P/Fe₂P as Efficient Bifunctional Electrocatalyst for Water Splitting

Developing efficient bifunctional electrocatalysts with excellent stability at high current densities for overall water splitting is a challenging yet essential objective. However, transition metal phosphides encounter issues such as poor dispersibility, low specific surface area, and limited electronic conductivity, which hinder the achievement of satisfactory performance. Therefore, this study presents the highly efficient bifunctional electrocatalyst of CeO₂-modified NiFe phosphide on nickel foam (CeO₂/Ni₂P/Fe₂P/NF). Ni₂P/Fe₂P coupled with CeO₂ was deposited on nickel foam through hydrothermal synthesis and sequential calcination processes. The electrocatalytic performance of the catalyst was evaluated in an alkaline solution, and it exhibited an HER overpotential of 87 mV at the current density of 10 mA cm⁻² and an OER overpotential of 228 mV at the current density of 150 mA cm⁻². Furthermore, the catalyst demonstrated good stability, with a retention rate of 91.2% for the HER and 97.3% for the OER after 160 h of stability tests. The excellent electrochemical performance can be attributed to the following factors: (1) The interface between Ni₂P/Fe₂P and CeO₂ facilitates electron transfer and reactant adsorption, thereby improving catalytic activity. (2) The three-dimensional porous structure of nickel foam provides an ideal substrate for the uniform distribution of Ni₂P, Fe₂P, and CeO₂ nanoparticles, while its high conductivity facilitates electron transport. (3) The incorporation of larger Ce³⁺ ions in place of smaller Fe³⁺ ions leads to lattice distortion and an increase in defects within the NiFe-layered double hydroxide structure, significantly enhancing its catalytic performance. This research finding offers an effective strategy for the design and synthesis of low-cost, high-potential catalysts for water electrolysis.