Nonmetallic Modified Atomically Precise Octagold Nanoclusters for Electrocatalytic Nitrate Reduction to Ammonia

Area of Science:

• Nanomaterials Chemistry
• Electrocatalysis
• Surface Science

Background:

• Atomically precise metal nanoclusters (NCs) functionalized with nonmetallic elements show potential for electrocatalytic nitrate reduction reaction (NO3RR).
• Challenges exist in understanding structural changes during catalysis and identifying active sites in these NCs.

Purpose of the Study:

• To synthesize and characterize sulfur- and selenium-modified gold nanoclusters ([Au8S2(dppm)4]2+ and [Au8Se2(dppm)4]2+).
• To investigate the structural evolution and active site identification of these NCs during electrochemical pre-activation for NO3RR.
• To evaluate the catalytic performance and elucidate the mechanism of sulfur-modified gold nanoclusters in NO3RR.

Main Methods:

• Synthesis of [Au8S2(dppm)4]2+ and [Au8Se2(dppm)4]2+ nanoclusters.
• Electrochemical pre-activation treatment.
• Comprehensive experimental characterization including electrochemical measurements and mechanistic studies.
• Density Functional Theory (DFT) calculations to analyze electronic structure and adsorption properties.

Main Results:

• Electrochemical pre-activation removed a dppm ligand, exposing metallic Au sites.
• Activated [Au8S2(dppm)4]2+ achieved a high NH3 yield rate (1108.47 mg h-1 mgAu-1) and Faradaic efficiency (98.34%) for NO3RR.
• Sulfur modification led to a more positive surface potential, upshifted Au-d band center, enhanced NO3- adsorption, and optimized hydrogen balance compared to selenium modification.
• Exposed metallic Au sites were identified as the primary catalytic centers.

Conclusions:

• Definitive experimental evidence for structural evolution and active-site identification in atomically precise NCs under electrolysis was provided.
• Sulfur incorporation in Au NCs significantly boosts NO3RR performance through beneficial electronic and surface effects.
• This study offers insights into designing advanced NC catalysts for efficient nitrate electroreduction.