Phase Segregation in Cu0.5 Ni0.5 Alloy Boosting Urea-Assisted Hydrogen Production in Alkaline Media.

Abstract

Coupling urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is promising for energy-efficient hydrogen production. However, developing cheap and highly active bifunctional electrocatalysts for overall urea electrolysis remains challenging. In this work, a metastable Cu0.5 Ni0.5 alloy is synthesized by a one-step electrodeposition method. It only requires the potentials of 1.33 and -28mV to obtain the current density of ±10mA cm-2 for UOR and HER, respectively. The metastable alloy is considered to be the main reason causing the above excellent performances. In the alkaline medium, the as-prepared Cu0.5 Ni0.5 alloy exhibits good stability for HER; and conversely, NiOOH species can be rapidly formed during the UOR due to the phase segregation of Cu0.5 Ni0.5 alloy. In particular, for the energy-saving hydrogen generation system coupled with HER and UOR, only 1.38V of voltage is needed at 10mA cm-2 ; and at 100mA cm-2 , the voltage decreases by ≈305mV compared with that of the routine water electrolysis system (HER || OER). Compared with some catalysts reported recently, the Cu0.5 Ni0.5 catalyst owns superior electrocatalytic activity and durability. Furthermore, this work provides a simple, mild, and rapid method for designing highly active bifunctional electrocatalysts toward urea-supporting overall water splitting.