A Te-Doping Strategy in Co@CoO for Concurrent Enhancement of Oxygen Evolution and Nitrate Reduction Reactions

Abstract

Developing bifunctional electrocatalysts for coupled nitrate reduction reaction (NitRR) and oxygen evolution reaction (OER) represents a promising route for simultaneous wastewater remediation and clean energy production, yet remains a significant challenge. Herein, an efficient Te-doped Co@CoO heterostructure supported on NiMo foam (Te-Co@CoO/NiMo) was synthesized. Structural characterizations reveal that Te doping not only modulates the electronic structure of Co sites to optimize intermediate adsorption but also facilitates surface reconstruction into highly active Te-doped CoOOH species during oxidation. Consequently, the catalyst exhibits excellent bifunctional performance. For OER, it delivers a current density of 100 mA cm-2 at a low overpotential of 330 mV, comparable to commercial RuO2, with robust stability over 60 hours. For NitRR, the electrode achieves a maximal Faradaic efficiency (FE) of 88.5% and an NH3 yield rate of 0.14 mg h-1 cm-2 at -0.7 V vs. RHE, effectively suppressing the competitive hydrogen evolution. In batch electrolysis purification, the catalyst demonstrates a nitrate removal efficiency of 75.8% (reducing concentration from 50 to 12.1 mg L-1) and a high selectivity for ammonium conversion (79.9%) with negligible nitrite accumulation. This work provides a viable strategy for designing durable bifunctional catalysts for energy-saving electrochemical pollutant degradation.