Electrocatalytic Reduction of Nitrate via Co(3)O(4)/Ti Cathode Prepared by Electrodeposition Paired With IrO(2)-RuO(2) Anode

Nitrate pollution is already a global problem, and the electrocatalytic reduction of nitrate is a promising technology for the remediation of wastewater and polluted water bodies. In this work, Co(3)O(4)/Ti electrodes were prepared by electrodeposition for the electrocatalytic reduction of nitrate. The morphology, chemical, and crystal structures of Co(3)O(4)/Ti and its catalytic activity were investigated. Then, the electrocatalytic nitrate reduction performance of Co(3)O(4)/Ti as the cathode was evaluated by monitoring the removal efficiencies of nitrate (NO(3) (−)-N) and total nitrogen (TN), generation of reduction products, current efficiency (CE), and energy consumption (EC) at different operating conditions. Under the catalysis of Co(3)O(4)/Ti, NO(3) (−) was reduced to N(2) and NH(4) (+), while no NO(2) (−) was produced. After the introduction of chloride ions and IrO(2)-RuO(2)/Ti as the anode, NH(4) (+) was selectively oxidized to N(2). The removal efficiencies of NO(3) (−)-N (at 100 mg/L) and TN after 2 h were 91.12% and 60.25%, respectively (pH 7.0; Cl(−) concentration, 2000 mg/L; current density, 15 mA/cm(2)). After 4 h of operation, NO(3) (−)-N and TN were completely removed. However, considering the EC and CE, a 2-h reaction was the most appropriate. The EC and CE were 0.10 kWh/g NO(3) (−)N and 40.3%, respectively, and electrocatalytic performance was maintained after 10 consecutive reduction cycles (2 h each). The cathode Co(3)O(4)/Ti, which is prepared by electrodeposition, can effectively remove NO(3) (−)-N, with low EC and high CE.