Subnanometric Nickel Phosphide Heteroclusters with Highly Active Ni<sup>δ+</sup>–P<sup>δ−</sup> Pairs for Nitrate Reduction toward Ammonia
Qi Hu, Chunyan Shang, Xinbao Chen, Shuai Qi, Qihua Huo, Hengpan Yang, Chuanxin He
Abstract
The development of efficient electrocatalysts for the neutral nitrate reduction reaction (NO 3 – RR) toward ammonia (NH 3 ) is essential to address the environmental issues caused by NO 3 – but remains considerably challenging owing to the sluggish reaction kinetics of NO 3 – RR in neutral media. Herein, we report subnanometric heteroclusters with strongly coupled nickel–phosphorus (Ni–P) dual-active sites as electrocatalysts to boost the neutral NO 3 – RR. Experimental and theoretical results reveal that the subnanometric feature of Ni–P heteroclusters promotes the electron transfer from Ni to P, generating Ni δ+ –P δ− active pairs, in which Ni δ+ species are highly active for the NO 3 – RR and P δ− tunes the interfacial water hydrogen bonding network to promote the water dissociation step and accelerate proton transfer during the NO 3 – RR. Consequently, in the neutral NO 3 – RR, Ni–P heteroclusters exhibit a large NH 3 yield rate of 0.61 mmol h –1 cm –2 at −0.8 V versus reversible hydrogen electrode, which is 2.8- and 3.3-fold larger than those on Ni–P nanoparticles and Ni clusters, respectively, and the generated NH 3 exists as NH 4 + in electrolytes. This study offers an efficient approach to boosting electrocatalytic reactions with multiple intermediates by designing subnanometric heteroclusters with strongly coupled active sites.