Vajithmeeran Kadharbatcha, Raja Arumugam Senthil, Anuj Kumar, Sieon Jung, Myong Yong Choi
In this work, we report the rational design of an interfaced NiO/RuO2 composite synthesized for the first time using an ultrafast CO2 laser thermal shock approach. This process transforms Ru-doped Ni(OH)2 precursors into NiO/RuO2 composites within 2 min under open-atmosphere conditions, offering a promising route for fabricating metal oxide nanomaterials. Among the series, the NiO/RuO2-3 composite, prepared with an equimolar ratio of Ni and Ru precursors, exhibits exceptional dual-functional electrocatalytic activity, requiring only 35 mV overpotential for the hydrogen evolution reaction (HER) and 1.38 V vs. the reversible hydrogen electrode for the urea oxidation reaction (UOR) at 10 mA·cm-2. When integrated into urea-assisted water splitting, the NiO/RuO2-3 composite achieves H2 generation at a low cell voltage of 1.43 V at 10 mA·cm-2, while showing remarkable stability over 100 h. In situ Raman spectroscopy reveals negligible surface reconstruction during the HER but distinct NiOOH formation during the UOR at the NiO/RuO2-3 interface. Meanwhile, density functional theory results corroborate that RuO2 modulates the electronic structure of NiO, optimizes the adsorption energetics of key intermediates, and accelerates both HER and UOR activities. This study proves that a CO2 laser-induced NiO/RuO2 composite is an efficient dual-functional electrocatalyst for energy-saving H2 production with concurrent wastewater remediation.