Dense Heterointerfaces and Unsaturated Coordination Synergistically Accelerate Electrocatalysis in Pt/Pt₅P₂ Porous Nanocages

Abstract Designing cost‐effective and durable Pt‐based catalysts is vital and challenging for practicable energy storage and conversion technologies. Here, a fast phosphating strategy to establish a Pt/Pt₅P₂ porous nanocage with numerous heterointerfaces and defects is presented. It exhibits extraordinary activity and stability for both hydrogen evolution reaction (HER) with a small overpotential of 29 mV at 10 mA cm⁻² and methanol oxidation reaction (MOR) with a high mass activity of 1.37 A mg⁻¹_Pt at peak values, surpassing Pt/C. Microstructural analyzes show that many stacking faults are induced around heterointerfaces, while rich vacancies and atomic steps are created by the phosphorus‐induced thermal migration of Pt atoms, serving as highly active low‐coordination sites. X‐ray absorption spectroscopy and theoretical calculations reveal that introducing P atoms can modify the electronic configuration of Pt, thus optimizing H₂O/H* binding strength and lowering water dissociation energy to accelerate HER, while decreasing the energy barrier of the rate‐limiting step (*CHO to *HCOOH) to facilitate MOR.