Advances in bifunctional catalysts for urea electrooxidation synergized with hydrogen evolution reaction
Urea electrolysis technology achieves the synergistic hydrogen production at the cathode by coupling anodic electrochemical urea oxidation.It is of great importance for green treatment of urea-rich wastewater and energy-saving hydrogen production.The key to its application lies in the design and construction of effiicient and stable UOR(urea oxidation reaction)and HER(hydrogen evolution reaction)catalysts.Compared with adopting different catalysts,the use of bifunctional catalysts active for UOR and HER not only simplifies the electrolyzer configuration,but also effectively avoids the inherent incompatibility and the side reactions triggered by different catalysts at the anode and cathode.For this reason,the research progress of bifunctional catalysts for urea electrolysis was reviewed.Furthermore,the design development strategies and performance reinforcement mechanisms of nickel-based(nickel nitride,nickel phosphide,nickel sulfide,nickel oxide and their composites),cobalt-based and nickel-cobalt-based bifunctional catalysts were categorically reviewed.In addition,the UOR/HER characteristics and electrolyzer performances of the typical bifunctional catalysts for urea electrolysis were summarized.Finally,the future directions of bifunctional catalysts for urea electrolysis are prospected,aiming to provide a reference for promoting its applications.