Abstract

Urea-assisted water electrolysis offers an effective strategy to significantly lower the cell voltage required for hydrogen production, while the development of efficient and earth-abundant bifunctional electrocatalysts has attracted considerable attention. Here, we present crystalline cobalt hydrogen phosphite as a bifunctional electrocatalyst, facilitating both cathodic hydrogen production and anodic urea oxidation. Surface reconstruction is demonstrated, leading to the formation of oxyhydroxides, which act as active sites for electrocatalysis. Notably, achieving a current density of 10 mA cm–2 requires ultralow potentials of −59 mV for the cathodic reaction and 1.302 V for the anodic reaction. Additionally, an overall cell voltage of 1.376 V is achieved to sustain the same current density in a two-electrode hybrid water electrolysis system, which is considerably lower than that required for traditional water splitting (1.577 V). This newly developed bifunctional electrocatalyst shows great promise for future energy-saving hydrogen production and urea-related wastewater treatment applications.