Effective design of promising photoanode using modified α-Fe2O3 thin film for improving photoelectrochemical water splitting

Abstract

Solar energy is one of the most abundant and stable natural resources, which could be an ideal alternative to traditional fossil fuels. Many research groups up today work in the production and utilization of renewable energy to replace fossil fuels. The photoelectrochemical (PEC) systems as an approaching way to address the global energy crisis can successfully convert the abundant solar energy harvesting into the storable chemical fuel. The PEC hydrogen production via water splitting can efficiently enable energy production to zero carbon emissions, which employs semiconducting materials as photoelectrodes for the direct conversion of solar energy into storable hydrogen. The photoanode used in such a system should have a suitable band position and harvest more portion of solar light spectrum along with superb stability for water oxidation while having a reasonable cost. Hematite (α-Fe2O3) is one of the most promising metal oxides which have been used as a photoanode in PEC cells. It is not only highly naturally abundant, environmentally friendly, and low cost, but it also has a narrow bandgap (1.9‐2.2 eV) and photochemical stability. However, the drawbacks of α-Fe2O3 (i.e., the short hole diffusion length (LD is around 2-4 nm) and poor conductivity) result in inconformity in the energy level of conduction band compared to the energy level of the H2/H+ reduction reaction. To decrease these drawbacks affecting the PEC performance of α-Fe2O3, various techniques have been examined. In this thesis, doping technique particularly using metals and heterojunction with other semiconductors have been widely applied to obtain improved PEC performance, and highlights the challenges faced in the design of visible light active water splitting photocatalysts.