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

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 <i>n</i>-hexylphosphonic acid (HPA), which simultaneously serves as the phosphorus source, soft template, and carbon precursor. <i>In situ</i> 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 (<i>vs.</i> 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.