Phase Segregation of Ni1mn1 Alloy Enable Efficient for Urea Electrolysis

Abstract

To alleviate urea wastewater pollution and achieve sustainable hydrogen production, development of highly active, low-cost, and stable bifunctional catalysts is urgently required. Using a deposition method, NixMny/NF (x=1, y=1) alloy materials were successfully synthesized, which can effectively generate hydrogen across full pH range. The overpotentials (η100) of Ni1Mn1/NF in alkaline, acidic, and neutral solutions were 197, 261, and 338 mV, respectively. During the urea oxidation reaction (UOR), HRTEM, XPS, and in-situ Raman results confirmed that the NiMn alloy undergoes reconstruction into a highly active composite structure NiMn/NiMnOOH, achieving an η100 of just 1.384 V. Density functional theory (DFT) indicates that Mn incorporation optimizes intermediate adsorption (Urea*)/desorption (CO2*), accelerating the deprotonation rate of the CONHN* intermediate (rate-determining step, RDS), thus enhancing catalytic activity. Notably, in the dual-electrode electrolyzer composed of Ni1Mn1/NF, the cell voltage in the overall human urine electrolysis system (HOUS) is 1.724 V@100 mA cm-2, which is approximately 333 mV lower than that in the overall water electrolysis system (OWS). Compared to recent studies, Ni1Mn1/NF demonstrates better catalytic activity and stability. This work presents a fresh perspective on catalyst design for mitigating urine pollution and enabling efficient hydrogen production.

Keywords: Bifunctional catalysts, Urea oxidation reaction (UOR), Phase-segregated Ni1Mn1/NF alloy, Human urine electrolysis system, Reconstruction