Near-Quantitative Electrochemical Upcycling of Halonitrobenzenes in Wastewater to Valuable Haloanilines over Facet-Engineered Copper Catalysts.

Selective electrocatalytic hydrogenation of halonitrobenzenes (HNBs) in wastewater to value-added haloanilines (HANs) offers a sustainable strategy for simultaneous pollutant abatement and resource recovery. However, achieving high HANs selectivity under ambient conditions remains challenging. Here we report a facet-engineered Cu electrocatalyst that enables selective hydrogenation of HNBs to HANs. Using p-chloronitrobenzene (p-CNB) as a model pollutant, the Cu catalyst achieves complete p-CNB removal with a 98.9% p-chloroaniline (p-CAN) selectivity. Mechanistic studies reveal that the outstanding performance of Cu originates from an optimal balance between moderate H* generation and facile desorption of the p-CAN product, which promotes efficient -NO2 to -NH2 reduction while effectively suppressing the over-dechlorination of p-CAN. Furthermore, it is found that the Cu(111) facet is intrinsically more active than Cu(200) and Cu(220), attributable to its higher p-CAN desorption ability. Guided by these insights, a Cu(111)-enriched electrode is rationally engineered, exhibiting an ultrahigh Faradaic efficiency of 99.4%. Finally, a tandem device integrating an electrolyzer and an extraction-distillation separation unit is developed, enabling the efficient recovery of high-purity p-CAN product. This study demonstrates a sustainable electrochemical pathway for converting hazardous pollutants into valuable chemicals, advancing low-carbon wastewater treatment and resource recovery.