From Solar Cells to Solar Fuels- Can We Do Better Than Mother Nature?
Kuei-Hsien Chen1*, Indrajit Shown1, Li-Chyong Chen2
1IAMS, Academia Sinica, Taipei, Taiwan
2CCMS, NTU, Taipei, Taiwan
* Presenter:Kuei-Hsien Chen,
Photocatalytic carbon dioxide (CO2) conversion to hydrocarbon fuels, making possible simultaneous solar energy harvesting and CO2 reduction, is considered as a two-birds-with-one-stone approach to solving the energy and environmental problems. However, the development of solar fuels has been hampered by the low conversion efficiency and lack of product selectivity of the photocatalysts. Here, we present defect engineering in some novel 2D materials, particularly, the carbon-doped SnS2 (abbreviated as SnS2-C) nanosheets and reduced graphene oxides, as a viable method towards promising photocatalysts for CO2 reduction reaction (CO2RR).
For the first case, the SnS2-C nanosheets with a typical layer thickness of ~40 nm were synthesized using an L-cysteine-based hydrothermal process. Compared with undoped SnS2, the interstitial carbon doping induced microstrain in the SnS2 lattice, resulting in different photo-physical properties. Density functional theory calculations were performed for differently configured SnS2-C for CO2RR. The SnS2-C exhibited a highly effective photo-catalytic activity in gas phase with a photochemical quantum efficiency exceeding 0.7 % under visible light, which is ~250 times higher than that of its un-doped counterpart, and also a world-record high value reported for inorganic catalyst.
For the second case, the MoS2 single layers were prepared by chemical vapor deposition, followed by hydrogen plasma post-treatment. With increasing hydrogen plasma treatment time, we observed blue-shift in the A1g peak and red-shift in E2g peak in their Raman spectra, implying creation of sulfur vacancies, with Mo/S ratio confirmed by X-ray photoelectron spectroscopy. In addition, scanning tunneling microscopic images clearly supported that there were missing atoms in the MoS2 layers after hydrogen plasma treatment. Both the hydrogen evolution reaction (HER) and CO2RR were measured for the MoS2 single layers with different Mo/S ratios. The role and interplay of the defects and the hosting materials as well as their effects on the HER and CO2RR will be discussed.

Keywords: Solar fuels, CO2 reduction, Photocatalyst, Nanostructures, 2D materials