# Activating Janus charge distribution on the P-doped Ni3S2/Co9S8 interface for enhancing charge-matched urea adsorption: boosting high current hydrogen production via coupled urine degradation

## TL;DR

This paper introduces a new electrocatalyst that improves hydrogen production and urea degradation by enhancing charge distribution at a material interface.

## Contribution

The novel use of phosphorus to activate a Janus charge distribution in a Ni3S2/Co9S8 interface for efficient urea oxidation and hydrogen production.

## Key findings

- P-doped Ni3S2/Co9S8 achieves ultralow potentials for urea oxidation at high current densities.
- The catalyst enables stable H2 production at 1000 mA cm−2 for 180 hours using alkaline urine as the electrolyte.
- The Janus charge distribution enhances urea adsorption and electron transfer for improved electrocatalytic performance.

## Abstract

The urea oxidation reaction (UOR) is emerging as a thermodynamically favorable alternative to the oxygen evolution reaction, offering significant potential for energy-efficient H2 production and simultaneous treatment of urea-rich wastewater. However, the 6 e− transfer process of the UOR results in sluggish kinetics, necessitating the development of highly efficient electrocatalysts. Herein, a Janus charge distribution surface is constructed by incorporating phosphorus (P) into the Ni3S2/Co9S8 heterojunction to enhance the UOR performance and accelerate urea-assisted H2 production. The P incorporation facilitates electron transfer from Ni3S2 to Co9S8, creating a local electrophilic/nucleophilic interface that enhances the adsorption of urea molecules with the electron-withdrawing C

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O group and electron-donating amino groups. As a result, the modified P-Ni3S2/Co9S8 exhibits ultralow potentials of 1.22, 1.30 and 1.39 V (versus the reversible hydrogen electrode) to reach 10, 100 and 1000 mA cm−2 for the UOR, respectively. Remarkably, when alkaline urine is used as the electrolyte, the P-Ni3S2/Co9S8 catalyst, functioning as a bifunctional electrocatalyst in an anion-exchange membrane electrolyzer, can stably deliver a high current density of 1000 mA cm−2 for H2 production over 180 h. This work highlights the importance of designing electrocatalysts by activating interfacial charge distribution to enhance reactant adsorption and trigger chemical bond cleavage.

Incorporating P into Ni3S2/Co9S8 creates Janus charge distribution for enhancing urea adsorption and electron transfer, thus boosting the UOR performance. Optimized P-Ni3S2/Co9S8 enables efficient urine treatment and H2 production via HER coupling.