An etching–templating dual strategy for the in situ synthesis of carbon-supported iron metaphosphate and its application as an electrocatalyst

Abstract

Carbon-supported transition-metal phosphates have emerged as promising non-noble electrocatalysts, but their poor conductivity and structural instability hinder their practical application. Here, we report a novel etching–templating dual strategy that enables the structural directing construction of carbon-supported iron metaphosphate nanocatalysts. The process is driven by n-hexylphosphonic acid (HPA), which simultaneously serves as the phosphorus source, soft template, and carbon precursor. In situ etching and templating yields a lamellar Fe–HPA intermediate with pre-organized Fe²⁺, phosphate, and alkyl components. The subsequent two-step heat treatment carbonizes the alkyl chains into a conductive matrix, enhances graphitization, and ensures uniform dispersion of Fe(PO₃)₂ nanocatalysts. The obtained carbon flake supported Fe-metaphosphate nanodots demonstrate a high oxygen–reduction reaction (ORR) onset potential of 0.85 V (vs. RHE) and a pseudo-four-electron transfer pathway. This work introduces a scalable templating strategy for one-pot integration of active metal phosphates and conductive carbon, offering a new platform for designing cost-effective electrocatalysts and beyond.