NiCo bimetal organic frames derived well-matched electrocatalyst pair for highly efficient overall urea solution electrolysis

Abstract The urea solution electrolysis for hydrogen evolution has attracted more and more attention due to its lower theoretical cell voltage than water splitting and the advantage to treat sewage containing urea. However, the electrolyzer assembled with highly efficient anode and cathode still remains a critical challenge. Herein, NiCo MOFs grown in situ on nickel foam (NiCo MOF/NF) were selected as the common precursor to conveniently prepare two well-targeted electrocatalysts for anodic urea oxidation reaction (UOR) and cathodic hydrogen evolution reaction (HER), respectively. The NiCo MOF/NF after electrochemical activation (NiCo MOF/NF-EA) in 1.0 M KOH displayed a prominent UOR catalytic activity with an ultra-low potential of 1.280 V vs RHE at 10 mA cm −2. The NiCo MOF/NF after phosphorization (NiCoP/NF) exhibited a high HER activity with a low overpotential of 63 mV at a current density of 10 mA cm−2. The overall urea solution electrolyzer assembled with superior NiCo MOF/NF-EA and NiCoP/NF showed an excellent performance with a voltage of 1.447 V to reach a current density of 10 mA cm−2 and a good long-term stability during 24-hour test. The strategy using the same precursor to conveniently synthesize different and optimal electrocatalysts for each electrode and assembling them together is effective for constructing efficient urea solution electrolyzer and worth extensive investigation.