Water splitting over new niobate photocatalysts with tungsten-bronze-type structure and effect of transition metal-doping

Barium titanate photocatalysts with silver-manganese dual cocatalyst for carbon dioxide reduction with water

Titanate photocatalysts with suitable cocatalysts are promising candidates for photocatalytic CO2 reduction, with the use of water as an electron donor. Here, several barium titanates with various compositions were examined, and BaTi4O9 (BT4) was found to be the best photocatalyst with the assistance of an Ag cocatalyst for photocatalytic CO2 reduction to form CO. The photocatalytic activity was further enhanced by the use of MnOx as an additional cocatalyst to construct an Ag-MnOx/BT4 photocatalyst, where Ag and MnOx were selectively deposited at different facets on BT4 crystal and functioned as active sites for CO2 reduction and water oxidation, respectively. As for the oxidative products from water, molecular oxygen (O2) and hydrogen peroxide (H2O2) were obtained.

Particulate Photocatalysts for Light-Driven Water Splitting: Mechanisms, Challenges, and Design Strategies

Solar-driven water splitting provides a leading approach to store the abundant yet intermittent solar energy and produce hydrogen as a clean and sustainable energy carrier. A straightforward route to light-driven water splitting is to apply self-supported particulate photocatalysts, which is expected to allow solar hydrogen to be competitive with fossil-fuel-derived hydrogen on a levelized cost basis. More importantly, the powder-based systems can lend themselves to making functional panels on a large scale while retaining the intrinsic activity of the photocatalyst. However, all attempts to generate hydrogen via powder-based solar water-splitting systems to date have unfortunately fallen short of the efficiency values required for practical applications. Photocatalysis on photocatalyst particles involves three sequential steps: (i) absorption of photons with higher energies than the bandgap of the photocatalysts, leading to the excitation of electron-hole pairs in the particles, (ii) charge separation and migration of these photoexcited carriers, and (iii) surface chemical reactions based on these carriers. In this review, we focus on the challenges of each step and summarize material design strategies to overcome the obstacles and limitations. This review illustrates that it is possible to employ the fundamental principles underlying photosynthesis and the tools of chemical and materials science to design and prepare photocatalysts for overall water splitting.