Advances in Modulating the Activity and Selectivity of Photocatalytic CO₂ Reduction to Multicarbon Products

Abstract

The emission of carbon dioxide (CO2) induced by the widespread use of fossil fuels has caused global warming and climate issues. Photocatalytic CO2 reduction technology, which utilizes solar energy to convert CO2 into carbon-based fuels, provides a promising sustainable green way to ameliorate the energy crisis and reduce CO2 concentration in the atmosphere. Multicarbon products (C2+) with higher energy density and larger market value attract widespread research interests. This review is focused on the recent progress of photocatalytic reduction of CO2 to C2+ products. Starting from the discussion on the fundamental mechanism of photocatalytic CO2 conversion to C2+ products, the strategies of photocatalyst design for C2+ fuels synthesis from CO2 are summarized. Particularly, the photocatalyst optimization approaches for improving the activity and especially selectivity of CO2 reduction reaction (CRR) to access C2+ products are highlighted. Finally, some personal outlook on this research direction of photocatalytic CRR to C2+ products is presented. This review is expected to evoke more research attention on the value-added C2+ fuels synthesis from solar energy powered CRR.

Electrochemical CO2/CO Reduction and C–C Coupling Path for Mimicking Fischer–Tropsch Synthesis over Cadmium Electrodes

“…The conversion of CO 2 into chemical fuels is a significant challenge for the future energy and environmental roadmap. − Two strategic approaches have been employed to accelerate this task, including the electrochemical CO 2 reduction (EC CO 2 R) method and the development of suitable electrodes. − Various pure metals from the periodic table have been extensively tested as electrodes for EC CO 2 R, showing different CO 2 reduction products such as CO and formate. The selectivity and productivity of these metals depend on their electron configuration and the nature of their surface states. − For instance, In and Sn in the p-block have shown high Faradaic efficiency (FE) and selectivity for formate production, − while Cu in group 11 has been found to be effective in producing CH 4 , C 2 H 4 , and alcohols. − Zn has been widely studied for producing syngas (CO and H 2 ) or CO. − However, cadmium (Cd), which belongs to the same group 12 as Zn, has relatively been less employed for CO 2 reduction. − Ongoing research on pure metals is opening up new CO 2 reaction pathways by using new reaction conditions such as electrolytes and surface engineering of support electrodes. − …”

Challenges in Photocatalytic Carbon Dioxide Reduction

“…Numerous chemical routes have been reported for the same, with *CO dimerization being the most popular one for C–C coupling, which can form products, e.g., C 2 H 5 OH and n -C 3 H 7 OH . Others reaction pathways also contain *CO–COH coupling, *CO–CHO coupling, and so on. , The interaction between the intermediates, the way CO 2 binds to the catalyst when one electron and one proton are transferred, the applied bias in relation to the onset potential, and the stability of the generated adsorbate all play major roles in determining the product selectivity. The CO 2 produced through CO 2 adsorption and activation has a tendency to react with the H atom, leading to the formation of a formate anion.…”

Materials Design for Photocatalytic CO2 Conversion to C2+ Products

“…The gray, red, and white colors indicate the carbon, oxygen, and hydrogen atoms, respectively. Reprinted with permission from ref . Copyright 2023, American Chemical Society.…”