An interesting route for the valorization of CO2 consists on its photocatalytic conversion into fuels and/or chemicals in the presence of water and suited photocatalyst ; this process is also known as Artificial Photosynthesis (AP). Such conversion is a quite challenging process since CO2 is a very stable compound and its reduction involves a series of multi-electron reactions. Extensive efforts are focused on improving the photocatalytic efficiencies, especially when using water as the electron donor. Generally, this process suffers from very low quantum yields and non-selective product distributions, due to the complexity of the involved multi-step reactions.
During the last years, a series of innovative materials with versatile properties and multifunctional character, known as hybrid materials, have been developed. Synergistic effects between their components provide these materials with exciting properties for light harvesting and charge separation, fundamental issues in artificial photosynthesis. Therefore, the development of new hybrid multifunctional photocatalysts using sunlight to produce fuels and chemicals is considered as a cornerstone for CO2 valorisation technologies.
In this work we report different strategies and modifications photocatalysts to increase process performance. The modification of optoelectronic properties of through the use of band gap engineering strategies, allow controlling the absorption of incident photons, redox capabilities and subsequently the photocatalytic performance. In addition, metal nanoparticles act as electron scavenger and as co-catalyst [2-3].
On the other hand, the use of novel hole transport materials maximize the light harvest and charge separation. On the other hand, efforts are devoted to shed light on mechanistic aspects of the reaction. In order to clarify the effect of different parallel and competitive reactions in the activity and products distribution, a series of photocatalytic experiments in combination with operando characterization using synchrotron radiation and laboratory techniques and theoretical calculations were performed.
These studies show that introduction of SPR NPs as co-catalyst or conductive polymers as hole transports leads to changes in the conversion and enhanced selectivity to higher demand electron products, such as CH4, while the CO and H2 concentrations decrease.