Current Trends And Future Roadmap For Solar Fuels

Solar to fuel conversion, if it could be performed in a sustainable manner, has the potential to deliver an alternative to unsustainable use of fossil fuels. Solar fuel production by photoelectrochemical (PEC) approach is a promising solution to address this fundamental and important challenge. To date, research into these approaches has been primarily focused on solar water splitting, which produces hydrogen. Thus, the conversion of CO2 to hydrocarbons that could displace currently used fossil fuels remains as an unmet challenge. Various photoelectrode materials such as Fe2O3, BiVO4, WO3, TiO2, and Cu2O have been discussed for solar water splitting. However, their performance for PEC water splitting is limited by poor electronic properties and sluggish charge transfer kinetics that lead to high charge carrier recombination. Nanostructuring, elemental doping, surface passivation, conducting template, cocatalyst, and heterostructure are possible pathways to improve their performance. Whereas only a few reports are available on PEC CO2 reduction. A number of semiconducting photocathodes including Si, GaP, InP, and CdTe have been explored for PEC CO2 reduction reaction (CO2RR), although most of these photocathodes produce only two electron products such as carbon monoxide or formate. This chapter reviews the state-of-the art limitations of various semiconducting photoelectrodes for PEC water splitting and CO2 reduction. Other emerging photoelectrode materials and tandem cell strategies are also discussed for efficient solar fuel production. This chapter concludes with the future prospects on the challenges and research direction in this cutting-edge research of solar fuels devices.