Sn induced NiO-RuO2-TiO2/Ti reconstruction for enhancing urea oxidation and hydrogen production through water electrolysis

Water electrolysis is an important technology for green hydrogen production, but the sluggish kinetics of the anodic oxygen evolution reaction (OER) lead to high overall energy consumption. Using the urea oxidation reaction (UOR) instead of OER has been considered an effective route for reducing potential and treating urea-containing wastewater. Here, we introduced Sn into RuO 2 -TiO 2 /Ti through three methods: electrodeposition, hydrothermal and ion exchange, and constructed a series of NiO-(Sn)-RuO 2 -TiO 2 /Ti electrodes. The systematic characterization showed that Sn was successfully introduced in the form of rutile SnO 2 , and the elements were evenly distributed. The Sn introduction method significantly affected morphology and electrocatalytic performance of electrodes: NiO-(Sn)-RuO 2 -TiO 2 /Ti-E prepared by electrodeposition method exhibited a compact nanosheet structure, high surface roughness and abundant exposed active sites, exhibiting the best activity in HER/OER, while NiO-(Sn)-RuO 2 -TiO 2 /Ti-I prepared by ion exchange method maintained its original morphology, and NiO nanoclusters were evenly dispersed, showing the best performance in UOR. The potential of NiO-(Sn)-RuO 2 -TiO 2 /Ti-I was only 1.39 V ( vs . RHE) at a current density of 100 mA cm −2 , and it operated stably for more than 132 h. When NiO-(Sn)-RuO 2 -TiO 2 /Ti-I was assembled into a HER‖UOR two-electrode system, the cell voltage at 100 mA cm −2 was only 1.65 V, which was 0.26 V lower than that of the traditional HER‖OER. This work reveals the modulating effect of Sn introduction method on the electrocatalytic performance of multi-component oxides, and provides a scalable solution for the advancement of energy-saving hydrogen production coupled with degradation of urea.