Abstract
Conventional catalysts based on the individual Oswin and Salomon (O-S) or Gerischer and Mauerer (G-M) mechanism cannot achieve direct electrocatalytic ammonia (NH(3)) oxidation into nitrogen (N(2)) with high activity and selectivity. Herein, a bimetallic nickel-cobalt oxyhydroxide (Ni(0.5)-Co(0.5)-OOH) with frustrated Lewis pairs was developed through an elaborate analysis of the binding types of NH(3) with the metal-oxide anode, efficiently integrating O-S and G-M mechanisms for converting NH(3) into N(2) with high activity (94%) and selectivity (63%), which is much superior to the anodes in the previous reports. The evidence of batch experiments, in situ characterization, and theoretical calculations confirms that two NH(3) molecules bind to Co(3+) sites (Lewis acid) in CoOOH and hydroxy sites (Lewis base) in NiOOH, respectively. Then, the NH(2(ads)) generated on the Lewis acid sites can quickly recombine with the NH(2(ads)) desorbed from the Lewis base sites, accelerating the formation of N(2)H(4(ads)) and preventing the peroxidation of NH(3). The electrocatalytic system assembled with the Ni(0.5)-Co(0.5)-OOH anode shows excellent performance for NH(3) elimination in the secondary aerobic process effluent. Our work provides precious guidance for the design of novel anodes and sheds light on further promoting the performance of ammonia conversion.