Carbon-Supported Fe2O3 and TiO2 Photoanodes for Enhanced Photoelectrochemical Cell Performance

Abstract

Since the worldwide demands for energy is increasing, the consideration of environmental issues has been sharply required. Developing clean, low-cost and renewable fuel sources is a key challenge facing mankind in order to meet the energy and environment demands. Electrolysis of water is one of the methods of hydrogen generation. However, it is an energy intensive process. To produce clean energy, such as hydrogen, photoelectrochemical (PEC) cell is widely considered as one of most promising methods to split water when driven by abundant solar energy. We have focused photoanode materials, hematite and titanium dioxide, which is one of PEC components. In the hematite case, we have shown that by coupling graphene inverse opal structure with hematite, the problem of low diffusion length and low absorption in hematite was efficiently addressed, and thereby the water splitting photocurrent density generated by hematite could be greatly enhanced. This study can be readily extended to other metal oxide materials and systems, which provide strong potential for our strategy in energy conversion system. In the case of titanium dioxide, we made heterojunction with cadmium selenide (CdSe) for visible range absorption. However, CdSe quantum dot is often unstable in water under irradiation of light due to their relatively slower interfacial hole transfer kinetics as compared to their electron injection rates. To overcome this problem, we have successfully fabricated a novel graphene quantum dot supported CdSe-sensitized photoanode for visible-working PEC system. By modifying photoanode with graphene quantumdot, photocurrent density was retained almost unchanged for 300 minutes irradiation and the photocurrent density increased by 1.2 times relative to that without graphene quantum dot. Our work suggests a straightforward way to develop efficient and durable quantum-dot-sensitized photoanodes for PEC hydrogen generation.