Recent progress of electrocatalysts towards urea electrolysis in alkaline media for energy-saving hydrogen production
Clean and renewable “hydrogen energy economy” era is coming. In this regard, the pathway for hydrogen production is of upmost importance. More recently, diligent urea (CO(NH2)2) electrolysis is explored as a more energy-saving promising avenue for sustainable hydrogen production in comparison with conventional water (H2O) electrolysis because of the low cell voltage, remediation of urea-rich wastewater and abundant electrocatalysts. A large amount of non-precious materials (especially nickel-based ones) are considered as the most electrocatalysts for urea electrolysis in alkaline media and massive efforts are continuously undertaking to better the kinetics and thermodynamics. In this review, we have firstly introduced the fundamentals of the energy-saving urea electrolysis system. Next, the recent advances of electrocatalysts for urea electrolysis are summarized. Then, the relationship between structure and activity are discussed. At last, the remaining challenges and future outlooks are pointed out for the development of advanced bifunctional electrocatalysts, new approaches for catalysts synthesis, solar-driven urea electrolysis and electrocatalytic mechanisms for Ni-free catalysts.