Artificial photosynthesis has been recognized as one of the most important strategies to convert sunlight into energy and chemicals. Semiconductor-based solar water splitting and CO2 photoconversion are promising strategies for the production of green hydrogen and C1/C2+ value-added products from a clean and sustainable source, following the global trend of replacing fossil fuels.
Although many efforts have been made after the first work reported the proof of concept for artificial photosynthesis using TiO2 as photocatalyst, challenges still exist to find materials with adequate properties to make artificial photosynthesis reaction a scalable process to practical application.
The major limitation of the efficiency of water splitting and CO2 photoconversion remains on the semiconductor photocatalyst material. The developments of stable materials with adequate band structure, capable of absorbing sunlight in the visible light spectrum range (narrow band gap), and charge separation of solid-solid and solid-liquid are the great challenges.
Whereas several materials, including Fe2O3 and TiO2, possess an adequate band structure and stability, most often their poor carrier mobilities and short hole diffusion lengths, which ultimately results in a low solar to fuel efficiency. The formation of heterojunction with two appropriated light-absorbing semiconductor materials (dual-absorbers) is a big bet to solve these issues. In this way, the overall objective of the project is the synthesis, study of their physical and chemical properties, and application of visible-light-active semiconductors materials in a single and dual-absorber configuration for the effective, selective, and stable production of green H2 from water splitting and conversion of CO2 into valuable chemical products, such as ethanol.
To reach this goal, the project will focus on six specific objectives:
- Development of visible-light-active nanostructured semiconductors materials: Fe2TiO5, CuFeO2, g-C3N4, Bi2MoO6, and BiVO4;
- Design photoactive dual-absorber junction using the target materials cited in (i). The dual-absorber configuration comprises the formation of a heterojunction of two semiconductors with suitable electronic properties to achieve improved solar-light harvesting and better performance in the charge separation and charge transfer, enhancing the oxidation and reduction half-reactions;
- Deposition of cocatalysts such as Pt, Ni, and Fe by magnetron sputtering to improve the charge separation, to increase the efficiency and reaction selectivity;
- Full understanding of the electronic and structural properties of individual material and dual-absorber junctions by IR, UV-Vis, Raman, XRD, XPS, and XAS, including the use of synchrotron light source facilities such as Sirius (BR), SLAC (USA), Diamond (UK) and Brookhaven (USA);
- Obtaining insights into the stability of the dual-absorber junctions to produce ethanol and H2 from CO2 and water for a long period of time (more than 100h) by artificial photosynthesis;
- Design and fabrication of microfluidic reactors adapted to convert CO2 into ethanol and H2 production by water splitting.
In order to overcome the global dependence on carbon-based fuels, hydrogen gas (H2) has been proposed as a clean and efficient alternative, since its use in combustion reaction or fuel-cell only produces water vapor as a by-product. In virtue of its small molecular weight, hydrogen fuel has a higher energy density per mass in comparison to fossil resources, thus facilitating its application in vehicles. Other valuable applications of H2 include the synthesis of ammonia (NH3) and hydrochloric acid (HCl), as well as the catalytic CO2-derived ethanol into valuable chemicals.
Brazil is a pioneer country in ethanol production through sugarcane plants. Despite the ethanol efficiently produced by sugarcane, this process ends in a large emission of CO2 to the atmosphere by the fermentation of glucose and by burning of the bagasse for electricity generation. In this scenario, an interesting window is opened to the conversion of the emitted CO2 into more valuable chemical products, especially, into ethanol generation, increasing the efficiency in sugarcane distillery production or any industrial process that emits large amounts of CO2.
TEAM
Project Coordinator: