Redox Replacement of Silver on MOF-Derived Cu/C Nanoparticles on Gas Diffusion Electrodes for Electrocatalytic CO2 Reduction

Ag-induced Phase Transition of Bi2 O3 Nanofibers for Enhanced Energy Conversion Efficiency towards Formate in CO2 Electroreduction

Bi-based electrocatalysts have been widely investigated in the CO₂ reduction reaction (CO₂ RR) for the formation of formate. However, it remains a challenge to achieve high Faradaic efficiency (FE) and industrial current densities at low overpotentials for obtaining both high formate productivity and energy efficiency (EE). Herein, we report an Ag-Bi₂ O₃ hybrid nanofiber (Ag-Bi₂ O₃ ) for highly efficient electrochemical reduction of CO₂ to formate. Ag-Bi₂ O₃ exhibits a formate FE of >90% for current densities from -10 to -250 mA ⋅ cm^-2 and attains a yield rate of 11.7 mmol ⋅ s^-1  ⋅ m^-2 at -250 mA ⋅ cm^-2 . Moreover, Ag-Bi₂ O₃ increased the EE (52.7%) by nearly 10% compared to a Bi₂ O₃ only counterpart. Structural characterization and in-situ Raman results suggest that the presence of Ag induced the conversion of Bi₂ O₃ from a monoclinic phase (α-Bi₂ O₃ ) to a metastable tetragonal phase (β-Bi₂ O₃ ) and accelerated the formation of active metallic Bi at low overpotentials (at > -0.3 V), which together contributes to the highly efficient formate formation.

Integrated carbon capture and conversion: A review on C2+ product mechanisms and mechanism-guided strategies

The need to reduce atmospheric CO₂ concentrations necessitates CO₂ capture technologies for conversion into stable products or long-term storage. A single pot solution that simultaneously captures and converts CO₂ could minimize additional costs and energy demands associated with CO₂ transport, compression, and transient storage. While a variety of reduction products exist, currently, only conversion to C₂₊ products including ethanol and ethylene are economically advantageous. Cu-based catalysts have the best-known performance for CO₂ electroreduction to C₂₊ products. Metal Organic Frameworks (MOFs) are touted for their carbon capture capacity. Thus, integrated Cu-based MOFs could be an ideal candidate for the one-pot capture and conversion. In this paper, we review Cu-based MOFs and MOF derivatives that have been used to synthesize C₂₊ products with the objective of understanding the mechanisms that enable synergistic capture and conversion. Furthermore, we discuss strategies based on the mechanistic insights that can be used to further enhance production. Finally, we discuss some of the challenges hindering widespread use of Cu-based MOFs and MOF derivatives along with possible solutions to overcome the challenges.

Redox Replacement of Silver on MOF-Derived Cu/C Nanoparticles on Gas Diffusion Electrodes for Electrocatalytic CO2 Reduction

Bimetallic tandem catalysts have emerged as a promising strategy to locally increase the CO flux during electrochemical CO₂ reduction, so as to maximize the rate of conversion to C-C-coupled products. Considering this, a novel Cu/C-Ag nanostructured catalyst has been prepared by a redox replacement process, in which the ratio of the two metals can be tuned by the replacement time. An optimum Cu/Ag composition with similarly sized particles showed the highest CO₂ conversion to C₂₊ products compared to non-Ag-modified gas-diffusion electrodes. Gas chromatography and in-situ Raman measurements in a CO₂ gas diffusion cell suggest the formation of top-bound linear adsorbed *CO followed by consumption of CO in the successive cascade steps, as evidenced by the increasingνC-H bands. These findings suggest that two mechanisms operate simultaneously towards the production of HCO₂ H and C-C-coupled products on the Cu/Ag bimetallic surface.