Understanding heterogeneous electrocatalytic carbon dioxide reduction through operando techniques

Abstract

Renewable energy conversion and storage play an important role in our global efforts to limit the drastic effects of climate change. In particular, the electrocatalytic reduction of carbon dioxide to chemicals and fuels can bring us closer towards a closed-loop anthropogenic carbon cycle. Significant breakthroughs are often the result of deeper understandings of reaction mechanisms, material structures and surface sites. To this end, operando techniques have been invaluable in combining advanced characterization of a catalyst with simultaneous measurements of its activity and selectivity under real working conditions. This Review aims to highlight significant progress in the use of operando characterization techniques that enhance our understanding of heterogeneous electrocatalytic CO2 reduction. We provide a summary of the most recent mechanistic understanding using operando optical, X-ray and electron-based techniques, along with key questions that need to be addressed. We conclude by offering some insight on emerging directions and prospects in the field.

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Fig. 1: Molecular model sketch depicting possible CO2RR roadmaps to form various C1 and C2 products.
Fig. 2: Analytical tools commonly applied in the characterization of catalyst materials.

Electron microscopy and tomography micrographs are adapted from ref. 116, Springer Nature.

Fig. 3: IR spectroscopy for operando measurements.

Figure adapted from ref. 117, RSC (ad); ref. 16, American Chemical Society (e); ref. 28, Wiley (f); and ref. 18, American Chemical Society (g).

Fig. 4: Various modifications of Raman spectroscopy setup to enable operando electrochemical measurements and improve detection sensitivity.

Figure adapted from ref. 32, American Chemical Society (a); ref. 44, Wiley (b); ref. 42, American Chemical Society (c); ref. 43, SNL (d); and ref. 20, American Chemical Society (e).

Fig. 5: X-ray techniques for operando electrochemical measurements.

Figure adapted from ref. 76, AIP Publishing (a); ref. 52, Wiley (b); ref. 59, Wiley (c); ref. 74, American Chemical Society (d); ref. 61, SNL (e); and ref. 78, RSC (f).

Fig. 6: Progress of in situ liquid phase TEM measurements.

Figure adapted from ref. 118, ECS (a,b); ref. 86, American Chemical Society (c,d); ref. 84, American Chemical Society (e,f); and ref. 88, RSC (g).

Fig. 7: Scanning-probe-microscopy-based techniques for operando electrochemical measurements.

Figure adapted from ref. 101, AAAS (ac); ref. 102, American Chemical Society (d); ref. 99, American Chemical Society (e); ref. 95, Wiley (f); and ref. 106, American Chemical Society (g).

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Acknowledgements

This work was supported by the Institute of Materials Research and Engineering, A*STAR (IMRE/17-1R1211) and the National University of Singapore (R-143-000-A08-114).

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Correspondence to Zhi Wei Seh.

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