Optimizing Intermediate Adsorption over PdM (M=Fe, Co, Ni, Cu) Bimetallene for Boosted Nitrate Electroreduction to Ammonia

Abstract

Electrochemical reduction of nitrate to ammonia (NO3RR) is a promising and eco‐friendly strategy for ammonia production. However, the sluggish kinetics of the eight‐electron transfer process and poor mechanistic understanding strongly impedes its application. To unveil the internal laws, herein, a library of Pd‐based bimetallene with various transition metal dopants (PdM (M=Fe, Co, Ni, Cu)) are screened to learn their structure‐activity relationship towards NO3RR. The ultra‐thin structure of metallene greatly facilitates the exposure of active sites, and the transition metals dopants break the electronic balance and upshift its d‐band center, thus optimizing intermediates adsorption. The anisotropic electronic characteristics of these transition metals make the NO3RR activity in the order of PdCu > PdCo ≈ PdFe > PdNi > Pd, and a record‐high NH3 yield rate of 295 mg h‐1 mgcat‐1 along with Faradaic efficiency of 90.9% is achieved in neutral electrolyte on PdCu bimetallene. Detailed studies further reveal that the moderate N‐species (*NO3 and *NO2) adsorption ability, enhanced *NO activation, and reduced HER activity facilitate the NH3 production. We believe our results will give a systematic guidance to the future design of NO3RR catalysts.