Transition-Metal-Free, Pure p-Block Alloy Electrocatalysts for the Highly Efficient Nitrate Reduction to Ammonia

Nitrate reduction to ammonia (NRA) is a promising technology, as it can remove polluting nitrate from sewage and transform it into value-added chemical products. Electrocatalysis has become a popular topic in recent years and has been naturally applied to electrochemical NRA. Currently, those reported metal electrocatalysts for NRA are predominantly based on transition metal (TM) elements and the reaction mechanisms on these catalysts were not well understood. Herein, using density functional theory (DFT) calculations, we propose unparalleled TM-free alloy catalysts, which are indium based and constituted by only p-block elements, for the electroreduction of nitrate to ammonia. Especially on the In3Sn(100) surface, we identified a novel reaction pathway along which the free energy evolution goes completely downhill, indicating an extraordinary performance in NRA. Additionally, proton adsorption was found to be extremely weak on the In3Sn(100) surface, resulting in substantial suppression of the parasitic hydrogen evolution reaction (HER). The intrinsically high activity and inhibition of the competing reaction on these p-block metal-based catalysts jointly contribute to their excellent performance in NRA.

Automated summary

In this study, TM-free alloy catalysts based on indium and p-block elements were proposed for the electroreduction of nitrate to ammonia, showing an extraordinary performance. A novel reaction pathway was identified on the In3Sn(100) surface, with the free energy evolution going completely downhill. In addition, proton adsorption was found to be extremely weak on the In3Sn(100) surface, suppressing the parasitic hydrogen evolution reaction. The high activity and inhibition of the competing reaction contribute to the excellent performance of these p-block metal-based catalysts in NRA.