AuNPs embedded in SiO2@TiO2 core-shells to boost H2 production: Optical and structural characterizations

The conversion of solar energy to chemical fuels, such as hydrogen (H2), as clean energy to replace the use of fossil fuels has gained significant attention. H2 is recognized as a green energy vector that is expected to solve the energy crisis and global warming issues. Photocatalysis is reported as a promising technology that could lead to the production of green H2 using photocatalytic materials. TiO2 coupled to Au nanoparticles was found to be an efficient combination that is capable of producing H2 under light excitation. Recently, our group found that covering Au nanoparticles (AuNPs) with a thin TiO2 overlayer significantly enhances hydrogen production. Furthermore, altering the location of the AuNPs within the structure (Au/TiO2 or TiO2/Au) greatly affects hydrogen production efficiency. The reasons behind this difference remain unclear and require further investigation. In our group, we developed a new electrochemical device coupled to
onlinear optical spectroscopy for in situ monitoring of the chemical intermediates and species that adsorb, desorb, or dissociate at the extreme surface of the photocatalysts during the photocatalytic production process. Sum-frequency generation (SFG) spectroscopy, which works as an effective in-situ optical probe for monitoring interfaces, enables us to observe and track the steps involved in production at the surfaces of these nanostructures. We have developed a technique for depositing these core-shell nanostructures onto suitable substrates and have characterized them both structurally and optically to gain a deeper understanding of these materials. The chemical signature of all the absorbed intermediates was monitored in situ, and an attempt to establish the reaction mechanism occurring during the photocatalytic process on each system is proposed. This study provides valuable insights into the mechanisms of photocatalytic hydrogen production, offering a foundation for the design of more efficient materials for green energy applications.