Carbon dioxide splitting into higher-value chemicals with hybrid photocatalyst sheets

Project Information

CO2SPLITTING

Grant agreement ID: 793996

DOI

10.3030/793996

Project closed

EC signature date 23 March 2018

Start date 1 September 2018

End date 31 August 2020

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 183 454,80

EU contribution

€ 183 454,80

Coordinated by

THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
United Kingdom

Periodic Reporting for period 1 - CO2SPLITTING (Carbon dioxide splitting into higher-value chemicals with hybrid photocatalyst sheets)

Reporting period: 2018-09-01 to 2020-08-31

Summary of the context and overall objectives of the project

The development of sustainable CO2-to-fuel conversion systems is a central issue in closing the global carbon cycle and producing renewable chemicals and fuels from the greenhouse gas CO2. However, efforts to demonstrate fuel production from CO2 powered by sunlight are currently hampered by the requirements of sacrificial electron donors or external bias, and lack of efficiency, selectivity and scalability. Ultimately, the CO2 reduction reaction (CO2RR) must be coupled with sustainable oxidation chemistry with an abundant electron source such as water for such technologies to satisfy global energy demands.

This work provides a novel approach to overcome those barriers and reports the first example of scalable and selective solar-driven CO2RR conjugated with water oxidation. A selective molecular catalyst was integrated on semiconductor light absorbers to form a wireless and monolithic photocatalyst sheet. Taking a phosphonated cobalt(II) bis(terpyridine) catalyst (CotpyP) modified SrTiO3:La,Rh|Au|BiVO4:Mo sheet as an example, the device combines the high selectivity of molecular catalysts for CO2 reduction and the strong water oxidation power of semiconductors. Hence, it provides a solar-to-formate conversion efficiency (STF) of 0.08±0.01% with selectivity for formate of 97±3%, setting a new benchmark in the field of wireless CO2 conversion using water as an electron donor. A benefit of the photocatalyst sheet configuration is that CO2RR and water oxidation occur in close proximity and the device, therefore, overcomes scale-up limitations inherent to (photo)electrochemical cell designs, where pH gradients and IR drop generated between the (photo)anode and (photo)cathode limit performance. Consequently, a comparable STF was observed even if the active area was increased 20 times.

This study overcomes the hurdle of current molecularly engineered systems requiring sacrificial reagents in photocatalytic CO2RR constructs, providing the impetus to study other molecular catalysts for solar fuel production via artificial photosynthesis in such architectures. The simplicity of the assembly process for integrating molecular catalysts in the device also allows the exploration of a wide range of catalysts for various photosynthetic reactions beyond CO2 utilisation to produce diverse products in the future.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A monolithic device (taking the SrTiO3:La,Rh|Au|RuO2-BiVO4:Mo sheet as an example) was designed and developed and immobilize a phosphonated cobalt(ii) bis(terpyridine) molecular catalyst (CotpyP as the CO2 reduction catalyst) onto the surface in a straightforward manner. Solar irradiation of the device delivered formate (HCOO‒) from aqueous CO2 with 97 ± 3% selectivity, accompanied by simultaneous O2 generation in a stoichiometric 2:1 ratio with a solar-to-formate conversion efficiency (STF) of 0.08 ± 0.01%. When the sheet device is irradiated with simulated sunlight, electron–hole pairs are generated in both SrTiO3:La,Rh and BiVO4:Mo. Electrons are transferred from the conduction band of BiVO4:Mo to the donor levels of SrTiO3:La,Rh through the gold layer. Electrons in SrTiO3:La,Rh reduce CO2 to HCOO‒ with the aid of the molecular complex functioning as a CO2RR cocatalyst while holes in BiVO4:Mo simultaneously oxidize water to O2 with RuO2 species serving as an oxygen evolution cocatalyst.

The novel outcomes and results pertaining to this project has been published in a top peer-reviewed journal (Nature Energy), as proposed in the DoA, and presented in academic conferences and seminars such as Workshop on Materials Chemistry for Solar Fuels Production 2019, The 3rd International Solar Fuels Conference (ISF-3)/International Conference on Artificial Photosynthesis 2019 (ICARP2019), The 3rd International Solar Fuels Conference (ISF-3) Young and Photonics and Optoelectronics Seminar. The paper published in Nature Energy has been allowed to release a self-archive the final author version under the green open access policy. The publisher also provides a link to a view-only version of the paper that can be publicly shared without restrictions. The data supporting the findings of the study are available in the paper and its supplementary materials. Source data supporting the findings of this study are available from the Cambridge data repository (https://doi.org/10.17863/CAM.54840). The funding was acknowledged in the paper acknowledgement.

Accompanied by the publishment in Nature Energy, the research was highlighted as News & Views in this journal due to the breakthrough in the artificial photosynthesis field. The publishing of this research has attracted enormous interest from the media and researchers, which can be proved by the high Altmetric score (550 since one month after the publication, which is 99th percentile (ranked 880th) of the 230,572 tracked articles of a similar age in all journals and the 95th percentile (ranked 2nd) of the 41 tracked articles of a similar age in Nature Energy). The research has also been introduced to the general public through the media around the world, including The Times, Times Radio, Voice of America, GMX News, China Daily and so on. The project and significant findings are presented on Reisner group’s homepage and Twitter. These approaches ensure that the important progress is communicated to the wider community reaches a wider audience in Europe as well as the rest of the world.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The development of the first stand-alone photocatalyst sheet for photocatalytic carbon dioxide (CO2) splitting into energy-rich chemicals using sunlight as the only energy source is the overall objective of this project. During this two years, the researcher and the host have successfully developed such device for scalable photocatalytic conversion of CO2 into liquid fuel with high solar-to-fuel efficiency and selectivity, setting a new benchmark in the field of wireless CO2 conversion using water as an electron donor.

Gigatons of CO2 as a greenhouse gas are released into the atmosphere worldwide, causing the environment issue and climate changes. CO2 conversion has therefore been suggested as a valid alternative carbon recycling by producing value-added chemicals and renewable fuels from CO2. The outcome of this study offers a novel and versatile strategy of photocatalytic CO2 conversion that would be applied in sustainable and practical solar fuel production. It would contribute to increasing Europe’s status and competitiveness in solar energy research and technological development. The European Union is a world leader in climate change action. This project could influence several European policy targets such as the climate action by reducing CO2 emissions, the energy policy by the improved use of renewables and the industry policy by the creation of new products, value chains and more efficient use of the resources.

News and Views-highlight

Article Metrics