Atomically dispersed Ni electrocatalyst for superior urea-assisted water splitting

Urea oxidation reaction (UOR) has been selected as substitution for oxygen evolution reaction ascribing to its low thermodynamic voltage as well as utilization of nickel as electrocatalyst. Herein, we report the formation of nickel single atoms (Ni-SAs) as exceptional bifunctional electrocatalyst toward UOR and hydrogen evolution reaction (HER) in urea-assisted water splitting. In UOR catalysis, Ni-SAs perform a superior catalytic performance than Ni-NP/NC and Pt/C ascribing to the formation of HOO-Ni-N4 structure evidenced by in-situ Raman spectroscopy, corresponding to a boosted mass activity by 175-fold at 1.4 V vs. RHE than Ni-NP/NC. Furthermore, Ni-SAs requires only 450 mV overpotential to obtain HER current density of 500 mA cm−2. 136 mA cm−2 is achieved in urea-assisted water splitting at 1.7 V for Ni-SAs, boosted by 5.7 times than Pt/C-IrO2 driven water splitting.