Single-atom catalysts for CO₂ electroreduction with significant activity and selectivity improvements

Area of Science:

• Computational materials science
• Catalysis
• Electrochemistry

Background:

• Single-atom catalysts (SACs) exhibit unique electronic structures and high activity in various reactions, but their performance origins remain unclear.
• SACs offer potential for reduced noble metal usage in applications like CO oxidation and fuel cells.
• Understanding SACs for CO2 electroreduction is crucial for developing efficient catalysts.

Purpose of the Study:

• To investigate the potential of single transition metal atoms anchored on defective graphene (M@sv-Gr or M@dv-Gr) as CO2 electroreduction catalysts.
• To identify promising SACs for specific CO2 reduction products like methanol and methane.
• To elucidate the fundamental origins of enhanced activity in SACs.

Main Methods:

• Density functional theory (DFT) calculations were employed to study CO2 electroreduction on various single-atom catalysts.
• Free energy profiles were calculated to assess catalytic activity and selectivity.
• The electronic structures and binding energies of adsorbates on SACs were analyzed.

Main Results:

• Several SACs demonstrated high selectivity for CO2 reduction over hydrogen evolution due to favorable adsorption of *COOH or *OCHO intermediates.
• Ni@dv-Gr and Pt@dv-Gr were identified as promising catalysts for CH3OH production (U_L = -0.41 V and -0.27 V, respectively).
• Os@dv-Gr and Ru@dv-Gr showed potential for CH4 production (U_L = -0.52 V).
• The Pt@dv-Gr catalyst exhibited a significantly reduced limiting potential for methanol production compared to existing catalysts.
• The enhanced activity of SACs was attributed to the lack of atomic ensembles, unique electronic structures, and orbital interactions, deviating from conventional scaling relations.

Conclusions:

• Single-atom catalysts anchored on defective graphene show great potential for efficient and selective CO2 electroreduction.
• Specific SACs, particularly Pt@dv-Gr, offer remarkable performance improvements for valuable chemical production.
• The study provides insights into the electronic origins of SAC activity, guiding future catalyst design.