Atomically Dispersed Ni–Cu Dual Sites: Efficient Electrocatalytic Conversion of 4-Nitrophenol to p-Aminophenol in a Hybrid Acid/Alkali Flow Electrolyzer

4-Nitrophenol (4-NP), a toxic and recalcitrant pollutant, necessitates effective remediation strategies. Here, a noble metal-free NiCu-NC electrocatalyst is developed, where dual atomic Ni–Cu sites are elegantly anchored on a rhombic dodecahedral nitrogen-doped carbon matrix, enabling selective electrochemical reduction of 4-NP into value-added p-aminophenol (4-AP). This catalyst achieves a low overpotential and a high Faradaic efficiency of 95.7% for 4-AP production. Density functional theory (DFT) calculations reveal that the NiCu dual-atom configuration minimizes the energy barrier for the rate-determining step, thereby enhancing catalytic performance. Furthermore, a hybrid acid/alkali flow electrolysis cell is designed to couple the cathodic 4-NP reduction with the anodic oxygen evolution. This system maintains stable operation for over 400 h while maintaining a high Faradaic efficiency (>91%) and near-complete conversion (99%) for valorization of 4-NP. This work demonstrates a practical electrocatalytic approach for pollutant transformation and chemical production with potential implications for wastewater treatment and resource utilization.