Low-Temperature Plasma-Constructed Ni-Doped W₁₈O₄₉ Nanorod Arrays for Enhanced Electrocatalytic Oxygen Evolution and Urea Oxidation

Surface engineering by doping and amorphization is receiving widespread attention from the perspective of the regulation of the electrocatalytic activities of electrocatalysts. However, the effective modulation of active sites on catalysts is still challenging. Herein, a straightforward and efficient method combining hydrothermal treatment with low-temperature plasma processing is presented to synthesize Ni-doped W₁₈O₄₉ nanorod arrays on carbon cloth with abundant oxygen vacancies (CC/WO-Ni-x). Mild plasma doping with Ni modifies the electronic structure of the W₁₈O₄₉ nanorod arrays, resulting in the formation of an amorphous structure that significantly reduces the electron transfer resistance. Additionally, the coupling with high-valent W⁶⁺ (derived from W₁₈O₄₉) leads to the partial preoxidation of doped Ni to form active Ni³⁺ species and oxygen vacancies. These features are collectively responsible for the remarkable oxygen evolution reaction (OER) and urea oxidation reaction (UOR) properties of CC/WO-Ni-4, for example, 10 mA cm^-2 current density, an overpotential of 265 mV required for the OER under 1.0 M KOH solution. The addition of 500 mM urea to the 1.0 M KOH solution decreases the overpotential required for the same current density from 265 to 93 mV. This study provides insights into the modification of surface structures and presents an effective strategy to optimize the electrocatalytic active sites and enhance the efficiency of multifunctional electrocatalysts.