Quantum Mechanical Screening of Single-Atom Bimetallic Alloys for the Selective Reduction of CO2 to C1 Hydrocarbons

Electrocatalytic Alloys for CO2 Reduction

Electrochemically reducing CO₂ using renewable energy is a contemporary global challenge that will only be met with electrocatalysts capable of efficiently converting CO₂ into fuels and chemicals with high selectivity. Although many different metals and morphologies have been tested for CO₂ electrocatalysis over the last several decades, relatively limited attention has been committed to the study of alloys for this application. Alloying is a promising method to tailor the geometric and electric environments of active sites. The parameter space for discovering new alloys for CO₂ electrocatalysis is particularly large because of the myriad products that can be formed during CO₂ reduction. In this Minireview, mixed-metal electrocatalyst compositions that have been evaluated for CO₂ reduction are summarized. A distillation of the structure-property relationships gleaned from this survey are intended to help in the construction of guidelines for discovering new classes of alloys for the CO₂ reduction reaction.

Single-Atom Catalysts of Precious Metals for Electrochemical Reactions

Single-atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO₂ reduction to methane or methanol production while suppressing H₂ evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N-doped covalent triazine frameworks, graphitic carbon nitride, S-doped zeolite-templated carbon, and Sb-doped SnO₂ surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested.

The importance of grand-canonical quantum mechanical methods to describe the effect of electrode potential on the stability of intermediates involved in both electrochemical CO2 reduction and hydrogen evolution

Grand canonical quantum mechanics was employed to investigate intermediates of CO₂ER under constant potential instead of constant charge.

Comparative single atom heterogeneous catalysts (SAHCs) on different platforms: a theoretical approach

The nature of SAHC interactions with the matrix is crucial as it controls the electronic structure of the atom, its charge, the coordination pattern and the overall catalytic ensemble. We have checked all these aspects by studying the same single atom in oxides, metals and carbon nitride.