Mechanistic understanding of the effect of alloying Au with Ni on N2 electroreduction into NH3: theoretical considerations. (7th November 2022)

• Record Type: Journal Article
• Authors: Ou, Lihui; Hu, Peiyu; Chen, Yuandao; Jin, Junling
• Is Part Of: New journal of chemistry. Volume 46:Number 45(2022)
• Page Start: 21911
• Page End: 21920
• Publication Date: 2022-11-07
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/d2nj04006a
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : It is shown that only associative distal mechanisms via the NNH2 intermediate can occur for N2 electroreduction because of the significantly lower formation barrier for NNH2 that that for NHNH at the Au1 Ni1 (111)/H2 O interface. Abstract : Bimetallic AuNi alloy electrocatalysts were theoretically designed to determine the effect of the alloying of Au with Ni on N2 -electroreduction activity and mechanism. Our calculated results indicate that increasing the Ni surface composition could facilely activate N2 molecules, which could be attributed to increasing the overpotential at electrochemical interfaces. Notably, we found that the Au1 Ni1 (111) alloy with medium Ni surface composition had the lowest N2 H-formation barrier and the highest barrier for HER, thus leading to the optimal N2 -electroreduction activity. This phenomenon can be explained by the commonly accepted Sabatier principle. The present studies indicated that the Au1 Ni1 alloy could remarkably decrease the barrier for initial N2 electroreduction into N2 H species as the rate-determining step at the pure Au(111)/H2 O interface and suppressed HER. Thus, AuNi alloy with the atomic ratio of 1 : 1 was employed to study the effect of the alloying of Au with Ni on the N2 -electroreduction mechanisms. The calculated results suggest that only the associative distal mechanism could occur at Au1 Ni1 (111)/H2 O interfaces. By contrast, the associative alternating and distal mechanisms could parallelly occur at pure Au(111)/H2 O interfaces. Thus, we can conclude that the alloying of Au with Ni not only facilitates N2 electroreduction but also changes the N2 -electroreduction pathways. The origin of the enhanced N2 -electroreduction activity was attributed to the greater electron transfer from the Au1 Ni1 (111)/H2 O interface to the empty π orbital of the adsorbed N2 molecule. Moreover, we also observed that Au atoms exhibited a negative ion property on the bimetallic AuNi alloy surface due to electron transfer from the transition metal Ni to Au. Our present study can offer a theoretical guideline for rationally designing and preparing highly active bimetallic Au-based alloy electrocatalysts for N2 electroreduction.