Highly efficient overall urea electrolysis via single-atomically active centers on layered double hydroxide

Anodic urea oxidation reaction (UOR) is an intriguing half reaction that can replace oxygen evolution reaction (OER) and work together with hydrogen evolution reaction (HER) toward simultaneous hydrogen fuel generation and urea-rich wastewater purification; however, it remains a challenge to achieve overall urea electrolysis with high efficiency. Herein, we report a multifunctional electrocatalyst termed as Rh/NiV-LDH, through integration of nickel-vanadium layered double hydroxide (LDH) with rhodium single-atom catalyst (SAC), to achieve this goal. The electrocatalyst delivers high HER mass activity of 0.262 A mg(-1) and exceptionally high turnover frequency (TOF) of 2.125 s(-1)at an overpotential of 100 mV. Moreover, exceptional activity toward urea oxidation is addressed, which requires a potential of 1.33 V to yield 10 mA cm(-2), endorsing the potential to surmount the sluggish OER. The splendid catalytic activity is enabled by the synergy of the NiV-LDH support and the atomically dispersed Rh sites (located on the Ni-V hollow sites) as evidenced both experimentally and theoretically. The self -supported Rh/NiV-LDH catalyst serving as the anode and cathode for overall urea electrolysis (1 mol L-1 KOH with 0.33 mol L-1 urea as electrolyte) only requires a small voltage of 1.47 V to deliver 100 mA cm(-2) with excellent stability. This work provides important insights into multifunctional SAC design from the perspective of support sites toward overall electrolysis applications. (c) 2022 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

Automated summary

This study reports a multifunctional electrocatalyst, Rh/NiV-LDH, which integrates NiV-LDH and Rh single-atom catalyst for efficient urea electrolysis and hydrogen fuel generation. The electrocatalyst demonstrates excellent activity in both HER and urea oxidation reactions, indicating its potential for wastewater purification and energy conversion. The research provides important insights and references for multifunctional SAC design.