Controlled Self-Template Synthesis of CoNiFe-PBA Hollow Structure with Enhanced Electrocatalytic Oxygen Evolution Reaction Activity
The microstructure and composition of electrocatalysts critically govern oxygen evolution reaction (OER) performance. This study reports a controlled self-template synthesis of hollow CoNiFe Prussian blue analogues (PBAs) and their phosphide derivatives with enhanced OER activity. Cobalt-nickel basic acetates with tunable metal ratios were first synthesized via a solvothermal method, followed by anion exchange with potassium hexacyanoferrate to form CoNiFe-PBAs, and subsequent phosphorization to obtain hollow CoNiFe phosphides (CoNiFe-PBA-Ps). Among these, the Co3Ni1Fe composition exhibits an optimal combination of reduced particle size and hollow architecture, resulting in more exposed active sites and increased electrolyte accessibility. The final Co3Ni1Fe-PBA-P displays a low overpotential of 273 mV at 10 mA cm−2 and a Tafel slope of 59 mV dec−1, outperforming other CoxNiyFe-PBA-Ps and many reported Co, Ni, Fe-based electrocatalysts. DFT calculations confirm that the improved activity stems from lower energy barriers of key OER intermediates. This work provides a versatile strategy to design multi-metallic hollow nanostructures with small particle size, offering new insights into the development of high-performance electrocatalysts.