Abstract

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If renewable power sources such as solar and wind could be used to produce chemical precursors and/or fuels, it would provide an alternative to mankind’s currently unsustainable use of fossil fuels and slow the rate of CO2 emission into the atmosphere [1,2]. Solar to chemical energy conversion by electrochemical and photoelectrochemical processes is a potentially promising approach to address this fundamental and important challenge.

Analogous to photovoltaics, driving the thermodynamically uphill redox reactions required for net solar to chemical energy conversion necessitates directional charge transport [3]. Additionally, in order to convert carbon dioxide to hydrocarbons, analogous to photosynthesis, one must manage multi-electron transfer reactions (e.g. 12 in the case of ethylene and ethanol), and potential losses in all parts of the system including the cathode, anode, electrolyte, and membrane must be minimized. It will be shown that optimized coupling of photovoltaics to electrolysis cells can be used to convert CO2 to C-C coupled products such as ethylene and ethanol with an overall energy conversion efficiency of over 5% [4]. While these and related approaches are promising, product separation and operational stability remain as challenges.

There has been impressive progress in laboratory-scale CO2 electrolysis [5]. While the current economics of direct competition with existing, petroleum-based production methods may be unfavorable, integration of CO2 conversion into existing petrochemical plants is an attractive alternative. On-site CO2 recycling (CCSR) in ethylene oxide production has a projected economic payback time as short as 1-2 years, depending the availability of low-cost electricity and the applicable carbon taxes [6]. The CCSR approach is applicable to other largescale chemical production processes including ammonia production. Wide-scale adoption of CCSR in chemical manufacturing has the potential to recycle between 4-10 Gta CO2 annually by 2050, representing ca. 50% of this industry’s carbon neutrality goal [7].

References:

1. Graves,C.; Ebbesen, S. D.; Mogensen, M.; Lackner, K. S. Renew. Sustain. Energy Rev. 2011,15, 1–23.

2. Chu, S.; Cui, Y.; Liu, N. The Path towards Sustainable Energy. Nat. Mater. 2016, 16, 16–22.

3. Osterloh, F. E. ACS Energy Lett. 2017, 2, 445–453.

4. Gurudayal; Bullock, J.; Srankó, D. F.; Towle, C. M.; Lum, Y.; Hettick, M.; Scott, M. C.; Javey, A.; Ager, J. W. Energy Environ. Sci. 2017, 10, 2222–2230.

5. Ager, J. W.; Lapkin, A. A. Science 2018, 360, 707–708.

6. Barecka, M. H.; Ager, J. W.; Lapkin, A. A. Energy Environ. Sci. 2021, 14, 1530–1543.

7. Barecka, M. H.; Ager, J. W.; Lapkin, A. A. iScience 2021, 102514

Speaker bio

Joel W. Ager III is a Senior Staff Scientist in the Materials Sciences Division of Lawrence Berkeley National Laboratory and an Adjunct Full Professor in the Materials Science and Engineering Department, UC Berkeley. He is a Principal Investigator in the Electronic Materials Program and in the Liquid Sunshine Alliance (LiSA) at LBNL and in the Berkeley Educational Alliance for Research in Singapore (BEARS). He graduated from Harvard College in 1982 with an A.B in Chemistry and from the University of Colorado in 1986 with a PhD in Chemical Physics. After a post-doctoral fellowship at the University of Heidelberg, he joined Lawrence Berkeley National Laboratory in 1989. His research interests include the discovery of new photoelectrochemical and electrochemical catalysts for solar to chemical energy conversion, fundamental electronic and transport properties of semiconducting materials, and the development of new types of transparent conductors. Professor Ager is a frequent invited speaker at international conferences and has published over 300 papers in refereed journals. His work is highly cited, with over 38,000 citations and an h-index of 102 (Google Scholar).