Self-Recycled electron donor resists disfavored oxidation reconstruction of Cu (I) -based electrocatalyst for nitrate removal by charge compensation.

The overuse of nitrate has led to the accumulation in natural water, being a globe issue in environment and human health. Electrochemical NO ₃ ^- reduction reaction (eNO ₃ RR) to ammonia occurs under ambient condition with low energy consumption and the yield of value-added product, being promising for NO ₃ ^- removal. Cu ^(I) -based eNO ₃ RR catalysts suffer from unavoidable oxidation reconstruction to Cu ^(II) , reducing the performance of NO ₃ ^- removal. In this work, we demonstrate charge compensation strategy to resist oxidation reconstruction of Cu ^(I) -based eNO ₃ RR catalysts by introducing self-recycled electron donor. Taking Ti ^(III) -modified Cu ₂ O/Cu as the proof-of-concept model, electron donor Ti ^(III) can donate electron to Cu ^(II) to regenerate Cu ^(I) , meanwhile the expended Ti ^(III) can be recycled from the generated Ti ^(IV) via intervalence charge transfer (IVCT). Benefiting from those, Ti-Cu ₂ O/Cu-10 exhibits significantly improved activity and durability for NO ₃ ^- removal compared to Cu ₂ O/Cu. The percentage of NO ₃ ^- removal keeps at ∼95.0 % with the initial concentration of 60 mg•L ^-1 NO ₃ ^- -N at -0.9 V vs. RHE in 15 consecutive cycling tests (corresponding to 30 h). This work presents a feasible strategy to resist oxidation reconstruction of Cu ^(I) -based eNO ₃ RR catalysts, making NO ₃ ^- removal more effective, more durable, and more sustainable.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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