Electronic Modulation of Nickel Cobalt Phosphide Nanosheets by Ce Doping for Efficient Overall Water Splitting

Abstract

Efficient hydrogen (H₂) generation from electrochemical overall water splitting (OWS) is key to a sustainable H₂ economy. Low-cost transition metal-based catalysts, such as Ni- and Co-based phosphides, have gained attention for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) due to their excellent corrosion resistance and high electrical conductivity. In particular, bimetallic Ni and Co-based phosphide catalysts are considered highly efficient electrocatalysts for OWS due to their abundant adsorption sites and low adsorption energy for hydrogen species. However, improving their stability and activity remains challenging. Herein, a Ce doping NiCo phosphide catalyst is presented with vary Ce amount (Ce_x-NiCoP) supported on nickel foam (NF) with multi-site functionality, achieving highly efficient HER performance comparable to benchmark platinum catalysts support carbon fiber or NF (Pt/C or Pt/NF). Comprehensive characterization results show that the optimal amount of Ce doping significantly influences the electronic structure of the catalyst, preventing the formation of Ni₅P₄ and CeO₂, promoting the dominant NiCoP phase. This modification enhances the catalyst's hydrophilicity, improving the HER activity significantly. Remarkably, the catalyst also demonstrates exceptional OER performance, making it a highly active and stable bifunctional catalyst for OWS, with the highest energy efficiency of 96.7%.