Facile Surfactant-Assisted Synthesis of Uniform NiO Nanospheres on Carbon Felt for Efficient Electrocatalytic Nitrogen Reduction

Nickel-based oxides have received extensive attention in electrocatalysis because of their cost-effective and tunable 3d orbital electronic structure; however, their research on the electrochemical nitrogen reduction reaction (e-NRR) is rarely reported. Herein, the synthesis of NiO nanospheres grown on carbon felt (NiO@CFs) is demonstrated by employing a surfactant-assisted hydrothermal reaction and high-temperature treatment. The influence of different types of surfactants on the morphology and e-NRR performance of NiO@CFs is systematically investigated. The utilization of CF as an excellent substrate for coating NiO can significantly improve the electrical conductivity and enhance the number of active sites. Furthermore, the formation of oxygen vacancies during the calcination process can help to transfer electrons into the antibonding orbitals of N-2 molecules, thereby promoting N-2 adsorption and activation. A typical sample NiO@CF-CTAB electrode exhibits an excellent ammonia electrosynthesis activity (NH3 yield rate: 34.21 mu g.mg(-1).h(-1); Faradaic efficiency: 6.7%) at -0.25 V versus reversible hydrogen electrode (vs RHE) due to the regular spherical structure of NiO with a diameter of 22.4 nm, high content of Ni3+, and oxygen vacancies in samples. This research provides significant implications for the design and synthesis of a low-cost, binder-free, and highly efficient e-NRR nickel-based nanosphere electrocatalyst.

Automated summary

Nickel-based oxides have attracted attention in electrocatalysis due to their cost-effectiveness and tunable electronic structure. However, their application in the electrochemical nitrogen reduction reaction (e-NRR) is limited. In this study, NiO nanospheres grown on carbon felt were synthesized using a surfactant-assisted hydrothermal reaction and high-temperature treatment. The use of carbon felt as a substrate improved electrical conductivity and increased active sites, while the formation of oxygen vacancies during calcination promoted N-2 adsorption and activation. The NiO@CF-CTAB electrode exhibited excellent ammonia electrosynthesis activity, making it a promising low-cost and binder-free electrocatalyst for e-NRR.