The energy and pollution dilemma has emerged as a significant worldwide issue and source of worry in recent years. Electrochemical reduction with water as the hydrogen donor source serves as a sustainable synthetic alternative route for green electrochemical synthesis without the use of hazardous and expensive reagents. Specifically, efficient and selective electrosynthesis of 4-aminophenol via electrochemical reduction of 4-nitrophenol (e-NPR) can be achieved at potentials lower than those of the hydrogen evolution reaction. Herein, this study represents the facile electrochemical synthesis of micro-structured nickel-iron phosphide on carbon paper (microNiFeP|CP) with high activity in catalyzing e-NPR at neutral pH. A series of controlled-potential electrolyses (CPEs) were utilized to thoroughly examine the electrolysis conditions, including the electrolyte pH, applied potential, and electrolysis duration, on the electrosynthesis of 4-AP. Under optimal conditions, the optimized microNiFeP|CP (microNiFeP|CPop) electrode exhibited e-NPR onset at 0.13 V vs. RHE. The microNiFeP|CPop electrode had a turnover rate of 7.25 ± 0.05 h-1 to generate 4-AP at 0.0 V vs. RHE. Moreover, it also had a high 4-NP conversion rate of 92.29 ± 1.47% and a high selectivity (85.77 ± 2.21%) to generate 4-AP after 8 hours of CPEs at -0.15 V vs. RHE, which generated 4-AP at a rate of 25.45 ± 1.73 μmole cm-2 h-1 in the H-cell. In addition, the scale-up electrosynthesis of 4-AP with a flow-type electrolyzer was also demonstrated. The 3-h electrolysis using the flow-type electrolyzer operation at -10 mA cm-2 resulted in a high 4-NP conversion (93.84 ± 0.84%) with a high SAP (86.32 ± 1.05%). Finally, the probable reaction pathways of e-NPR have been proposed, and the main side products have been identified as 4,4'-dihydroxyazobenzene and dimers.

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