Assembly of low-crystalline triple-phase NiCoSx nanospheres for efficient hydrogen production via urea electrolysis

It is highly desired to design high-performance electrocatalysts for urea oxidation reaction (UOR) that can be utilized for hydrogen production from urea-containing water, although this remains a significant challenge. In this study, low-crystalline NiCoS _x nanospheres derived from 2D NiCo-BDC-MeIM nanosheets arrays (lc-NCS _x/C-NC-BM) grown on nickel foam were synthesized using a facile hydrothermal method for UOR and hydrogen evolution reaction (HER). In contrast to the high-crystalline catalyst (hc-NCS _x/C-NC-BM), the lc-NCS _x/C-NC-BM possessed a multitude of unsaturated coordination sites with disordered atomic arrangements, thereby enhancing reactant adsorption, accelerating ion diffusion and facilitating charge transfer. Leveraging these characteristics, the as-prepared lc-NCS _x/C-NC-BM demonstrated significantly enhanced UOR activity (E _10/100= 1.2/1.33 V) and HER activity (E _−10/−100= −65/−222 mV) in 1 M KOH and 0.5 M urea solution. This study presents a rational approach for synthesizing low-crystalline materials, which is crucial for efficient and stable hydrogen production by using urea-containing wastewater.