Electrochemically Induced Cu-NiOOH/Cu2O/Cu Mesh Heteroarchitecture with Cu-Ni Dual Active Sites as Efficient Bifunctional Electrocatalyst for Urea-Assisted Energy-Saving Hydrogen Production in Alkaline Electrolyte

The electrocatalytic oxidation of urea combined with wastewater splitting is considered a promising approach for sustainable hydrogen production, characterized by minimal energy consumption. However, its evolution is greatly hindered by the shortage of efficient and easily accessible electrocatalytic materials. Here, a facile electrochemical activation strategy was conceived and proposed to construct a Cu-doped NiOOH nanolayer encapsulated on Cu2O nanodendrites on Cu mesh substrate (Cu-NiOOH/Cu2O/CM) from the electrodeposited Ni/Cu2O/CM heterostructured precatalyst. It was verified that the incorporation of Cu not only facilitates the rapid formation of Ni(III)species but also contributes to the formation of Cu-Ni(III)bifunctional electrocatalytic active sites. Benefiting from the accessible Cu-Ni(III)dual active sites, high active surface area, good hydrophilic and aerophobic surface properties and superior electrical conductivity of the Cu mesh substrate, the as-prepared Cu-NiOOH/Cu2O/CM exhibits enhanced bifunctional electrocatalytic abilities for electrocatalytic urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Particularly, for the Cu-NiOOH/Cu2O/CM||Cu-NiOOH/Cu2O/CM configuration toward the UOR||HER coupled system, a significantly reduced cell voltage of 1.43 V vs. RHE @ 10 mA·cm−2was obtained. The observed cell voltage for the conventional overall water splitting is approximately 190 mV higher than that observed for overall urea splitting. This study proposes a viable approach to achieve and optimize the bifunctional UOR/HER performance of NiOOH active species, which holds significant importance for efficient and stable hydrogen generation from urea-contaminated substandard water.