Ni–O–Ca Interfacial Electron Transfer Channels Engineered From Electroplating Sludge for Ultrafast 4‐Nitrophenol Reduction

Abstract The catalytic reduction of 4‐nitrophenol (4‐NP), a persistent environmental pollutant faces dual challenges reliance on noble metals and inefficient utilization of hydrogen radicals (H*). Meanwhile, nickel‐containing sludge generated by the electroplating industry, classified as hazardous waste has long posed significant disposal conundrums. Herein, we developed a noble metal‐free pyroxene‐type CaNi(Si 2 O 6 ) catalyst, synthesized from electroplating sludge, that simultaneously addresses these challenges through dynamically reconstructed Ni–O–Ca interface with oxygen vacancies and interfacial electron transfer channels. Ni@Ca‐195/20 establishes a self‐sustaining catalytic system, achieving a remarkable conversion of 96.8% with 0.1 mM NaBH 4 and 0.05 mg catalyst, while maintaining stability over 31 cycles in low concentration regimes. Integrated characterization combined with catalytic performance evaluation reveals an interfacial electron transfer mechanism: the engineered interface enables in situ reduction of Ni 2+ generates metallic electron‐deficient Ni δ+ species, enhancing 4‐NP − and BH 4 − adsorption through dual‐site coordination. Oxygen vacancies accelerate BH 4 − hydrolysis, while electron transfer channels sustain H* flux via Ca 2+ modulated charge equilibration. This work establishes a waste‐to‐functionality paradigm for designing defect‐engineered catalysts while advancing sustainable remediation of nitroaromatic pollutants.