A Te-doping strategy in Co@CoO for concurrent enhancement of oxygen evolution and nitrate reduction reactions

Abstract

Developing bifunctional electrocatalysts for the 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 characterization studies 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 the OER, it delivers a current density of 100 mA cm⁻² at a low overpotential of 330 mV, comparable to that of commercial RuO₂, with robust stability over 60 hours. For the 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 the concentration from 50 to 12.1 mg L⁻¹) and 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.