Cyclic voltammetric deposition of binder-free Ni-Se film on Ni foams as efficient bifunctional electrocatalyst for boosting overall urea-water electrolysis

The development of efficient and low-cost bifunctional electrocatalysts for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is highly challenging in urea-water-alkali electrolyzers. Herein, nickel-selenium electrocatalysts (denoted as Ni-Se) were controllably grown on Ni foam by a facile and simple cyclic voltammetric electrodeposition for overall urea electrolysis. Considering the good conductivity and high hydrophilic surface of Ni-Se@NF, the optimized Ni-Se electrocatalyst exhibited the eminent HER and UOR catalytic competence. In 1 M KOH with 0.33 M urea electrolyte, Ni-Se electrocatalysts required an overpotential of 181 mV for HER and potential of 1.347 V versus reversible hydrogen electrode for UOR to achieve a current density of 10 mA·cm−2. Additionally, the electrocatalyst showed good durability in both HER and UOR. Moreover, the electrolyzer assembled by Ni-Se electrocatalysts as electrode couple exhibited a remarkable activity with a small cell voltage of 1.41 V to reach 10 mA·cm−2 for overall urea-water electrolysis. [Display omitted] •Ni–Se catalyst is prepared by cyclic voltammetric electrodeposition.•The catalyst couple only needs 1.41 V to drive 10 mA·cm−2 for urea-water electrolysis.•The electrical conductivity effectively boosts the performance of Ni–Se toward HER and UOR.•The hydrophilicity of Ni–Se catalyst benefit gas-releasing reactions.