NiO–NiMoO<sub>4</sub> Nanocomposites on Multi-Walled Carbon Nanotubes as Efficient Bifunctional Electrocatalysts for Total Water Splitting
Qi Xue, Yun Wu, Jinbo Hao, Long Ma, Yuan Dang, Jun‐Jie Zhu, Yuanzhen Zhou
Abstract
Multicomponent synergistic regulation and defect design have been effective strategies to enhance the electrocatalytic activity of transition-metal oxides. In this work, NiO and NiMoO 4 nanocomposites on multi-walled carbon nanotubes (termed NiO–NiMoO 4 /mCNTs) are synthesized through a two-step method. Physical characterizations show NiO–NiMoO 4 /mCNTs have a well-defined NiO–NiMoO 4 structure, large specific surface area, and abundant oxygen vacancies. For oxygen evolution reaction (OER), NiO–NiMoO 4 /mCNTs deliver lower overpotential (277 mV) than NiO/mCNTs, NiO, and commercial RuO 2 nanocrystals at 10 mA cm –2 . For hydrogen evolution reaction (HER), NiO–NiMoO 4 /mCNTs still show the best HER activity, manifested by the smallest onset potential and the lowest Tafel. Density functional theory calculations show that the adsorption energies of hydrogen- and oxygen-containing intermediates on the NiO–NiMoO 4 /mCNTs surface have changed, which can lower the energy barriers required for HER and OER. The excellent electrocatalytic activity of bifunctional NiO–NiMoO 4 /mCNTs for OER and HER can be attributed to the synergy effect between NiO, NiMoO 4, and mCNTs. A symmetrical two-electrode water electrolyzer with NiO–NiMoO 4 /mCNTs as both the cathode and anode are constructed, which can reach a current density of 10 mA cm –2 and only requires 1.57 V.