Nitrogen can be electrochemically reduced to produce ammonia, which supplies an energy-saving and environmental-benign route at room temperature, but high-efficiency catalysts are sought to reduce the reaction barrier. Here, iron-doped α-MoO3 nanosheets are thus designed and proposed as potential catalysts for fixing N2 to NH3. The α-MoO3 band structure is intentionally modulated by the iron doping, which narrows the band gap of α-MoO3 and turns the semiconductor into a metal-like catalyst. Oxygen vacancies, generated by substituting Mo6+ for Fe3+ anions, are beneficial for nitrogen adsorption at the active sites. In 0.1 M Na2SO4, the Fe-doped MoO3 catalyst reached a high faradaic efficiency of 13.3% and an excellent NH3 yield rate of 28.52 μg h–1 mgcat–1 at −0.7 V versus reversible hydrogen electrode, superior to most of the other metal-based catalysts. Theoretical calculations confirmed that the N2 reduction reaction at the Fe–MoO3 surface followed the distal reaction path.
The development of alternative methods for sustainable dinitrogen (N 2 ) fixation to ammonia (NH 3 ) is a cutting-edge research area. The presence of external stimuli, such as non-thermal plasma, can boost the activation of the inert N 2 molecules under ambient temperatures and pressures, thereby generating value-added products such as NH 3 or other nitrogen-containing compounds. Binary alkali metal hydrides such as NaH and KH have recently shown intriguing properties in the plasma nitrogen fixation process. Herein we report the different chemical behaviors of a series of hydride composites consist of potassium hydride (KH) and alkaline earth metal hydride (MgH 2 , CaH 2 , SrH 2 , and BaH 2 ) under nitrogen plasma conditions. A nitrogen-relayed mechanism has been proposed to understand the different nitrogen fixation behaviors on these hydride composites. Under this scenario, KH is responsible for plasma N 2 fixation to form surface NH 2 species, which subsequently migrate and react with MgH 2 , CaH 2 , and SrH 2 to form N and NH species, respectively. This work enriches the plasma chemistry of metal hydrides , and provides a strategy to enhance the amounts of fixed nitrogen of single hydride material under nitrogen plasma conditions.
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