Transition Metal Dichalcogenides [MX2] in Photocatalytic Water Splitting

The quest for a clean, renewable and sustainable energy future has been highly sought for by the scientific community over the last four decades. Photocatalytic water splitting is a very promising technology to proffer a solution to present day environmental pollution and energy crises by generating hydrogen fuel through a “green route” without environmental pollution. Transition metal dichalcogenides (TMDCs) have outstanding properties which make them show great potential as effective co-catalysts with photocatalytic materials such as TiO2, ZnO and CdS for photocatalytic water splitting. Integration of TMDCs with a photocatalyst such as TiO2 provides novel nanohybrid composite materials with outstanding characteristics. In this review, we present the current state of research in the application of TMDCs in photocatalytic water splitting. Three main aspects which consider their properties, advances in the synthesis routes of layered TMDCs and their composites as well as their photocatalytic performances in the water splitting reaction are discussed. Finally, we raise some challenges and perspectives in their future application as materials for water-splitting photocatalysts.

Synergistic interplay of Zn and Rh-Cr promoters on Ga2O3 based photocatalysts for water splitting

The photocatalytic water splitting activity of a wide-bandgap material, Ga2O3, is greatly boosted with the addition of a Zn and Rh-Cr co-catalyst at optimum loadings. To date, however, the exact roles of the co-catalysts and particularly the origin of their synergistic functions have not been clarified. Herein, we present how the optimum Zn loading on Ga2O3 leads to creation of a ZnGa2O4/Ga2O3 heterojunction favorable for charge separation through information on the occupied and unoccupied electronic states of Zn and Ga elucidated by X-ray absorption and emission spectroscopic methods. The function of Rh-Cr as an electron sink and reduction site was proven by photocatalytic experiments using an electron scavenger (Ag+) and by learning where Ag deposits and its effects on photocatalytic activity. Finally, perturbation of the Zn electronic structure by photoactivation was evidenced by modulation excitation X-ray absorption spectroscopy. Importantly, Rh-Cr markedly enhanced the level of the perturbation, serving as proof of the direct communication and synergy between the electronic states of Zn, present in ZnGa2O4, and Rh-Cr deposited on Ga2O3.