One of society's great challenges for the 21st century is the development of alternative energy resources to help alleviate our reliance upon fossil fuels for energy. Hydrogen is considered to be one of the potential candidates especially if it can be generated form the photocatalytic conversion of cheap abundant H2O into clean non-carbon H2 from solar energy resources. Development of this clean, renewable form of energy will help to address our reliance on depleted fossil fuel supplies and the environmental problems accompanying its use. Photocatalytic splitting of water proceeds via generation of excited electrons and holes in the semiconductor catalyst bulk lattice, the diffusion of the excitons through the semiconductor lattice to the surface, and surface reactions of the excitons with water to split H2O to H2 and O2. The photocatalysis literature, however, has almost completely neglected the surface nature of the photocatalyst and focused on the semiconductor catalyst bulk lattice that is only responsible for generation of the excited holes and electrons. The supported (Rh2-yCryO3)/(Ga1-xZnx)(N1-xOx) photocatalyst is one of the most active photocatalyst under visible light water splitting (λ &gt; 400nm) with an optimized apparent photonic efficiency (PE) of 5.9%.1 In order to provide fundamental insights into the molecular and electronic structures of this leading photocatalyst system for splitting of water, the supported (Rh2-yCryO3)/(Ga1-xZnx)(N1-xOx) photocatalyst was extensively characterized with cutting edge surface and bulk characterization techniques. Bulk information was accessed with in situ optical spectroscopy [Raman, UV-vis, photoluminescence (PL) and time-resolved (TR) picosecond PL-Raman] and electron microscopy analysis (STEM and STEM-EDS). Surface information was obtained with surface characterization methods [in situ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and high-sensitivity low energy ion scattering (HS-LEIS)] that provide information on the nature of the surface region (~1-3nm) and outermost atomic layer (~0.3nm), respectively. These characterization tools were used to establish the fundamental structure-photoactivity relationship for this novel visible light active photocatalyst and give new insight into the true nature of the photocatalytic active sites.

Anatomy of a visible light activated photocatalyst for splitting of water

252nd National Meeting (2016)

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