Engineering Pt‐Ni Alloy Coral Nanoclusters with Efficient Oxygen Reduction: Enabling Endogenous Oxygen‐Mediated Sustainable Electrochemiluminescence for Breast Cancer Diagnosis

Abstract In biomedical diagnostics, endogenous oxygen‐mediated electrochemiluminescence (ECL) systems hold promise for avoiding toxic exogenous coreactants but are limited by sluggish oxygen reduction reaction (ORR) kinetics, a long‐standing, cross‐disciplinary challenge hindering ECL progress toward ultrasensitivity and sustainability. Herein, Pt‐Ni alloy coral‐like nanoclusters are prepared by tuning Pt/Ni precursor ratio and glucose template concentration. Acid etching created a thin Pt skin overlying the residual Pt‐Ni core, introducing >1.78% interfacial compressive strain. This hierarchical architecture, synergizing ligand and strain effects, enables a four‐electron ORR (49.56 mV dec −1 Tafel slope) that outperforms commercial Pt/C. Theoretical calculations confirmed that this design modulates electron distribution, downshifting the d ‐band center and weakening oxygen adsorption energy, thereby boosting ORR activity. Using dissolved oxygen as the coreactant, this Pt‐based catalyst sensitizes the ECL emission of graphitic carbon nitride nanoplates by 14.5‐fold while maintaining stability for >10 min, affording an ECL platform for breast cancer diagnosis via HER2 proteins and BT‐474 cells. It can discriminate HER2‐positive samples from negative ones, monitor HER2 expression across different cell lines, and dynamically track expression changes. This work not only overcomes ORR bottlenecks but also enables high‐performance, eco‐friendly ECL catalysts, further advancing the clinical translation of endogenous oxygen‐mediated ECL in precision oncology.