Modulating the electronic structure of Ni(OH)2 by coupling with low-content Pt for boosting the urea oxidation reaction enables significantly promoted energy-saving hydrogen production

Abstract

Replacing the high-potential oxygen evolution reaction (OER) by the low-potential nucleophile oxidation reaction (NOR) is an essential way to further promote the production rate of hydrogen during water electrolysis. Here, low-content Pt-anchored Ni(OH)₂ on the surface of nickel-carbon nanofibers (Ni-CNFs) are prepared via a simple electrospinning–electrodeposition strategy to achieve the alkaline urea oxidation reaction (UOR) electrocatalysis, and they are optimized by controlling different concentrations of deposition solutions during the electrodeposition process. Owing to the Pt loading on the Ni(OH)₂ surface, the dehydrogenation processes of both Ni(OH)₂ to Ni(OH)O and urea molecules to N₂ and CO₂ are promoted, leading to a greatly enhanced UOR performance with low potentials of 1.363 and 1.422 V vs. RHE at current densities of 10 and 100 mA cm⁻² for the optimized Pt–Ni(OH)₂@Ni-CNFs-2 catalyst, which is significantly better than many reported representative Ni-based catalysts. Moreover, considering the superior hydrogen evolution reaction (HER) activity of the optimized Pt@Ni-CNFs-2 catalyst through a similar synthetic procedure, a home-made urea-assisted water splitting device is constructed with the Pt–Ni(OH)₂@Ni-CNFs-2 and Pt@Ni-CNFs-2 catalysts serving as the anode and cathode, respectively, which exhibits a voltage of 1.40 V at 10 mA cm⁻², surpassing many reported representative urea-assisted water splitting electrolyzers. The as-fabricated electrolyzer displays a significantly promoted H₂ production rate of 10-fold that of the overall water splitting, demonstrating the prominent prospects of our catalysts in urea-assisted water splitting for energy-saving H₂ generation.