Graphene‐Based Solar‐Driven Water‐Splitting Devices

Abstract

IntroductionHuman beings are now experiencing the culmination of a fast growth period in economics and technology. But the huge consumption of fossil fuels and the severe deterioration of the environment have restricted the sustainable development of human society. Sufficiently utilizing clean and renewable energy resources is considered as the ultimate solution to the above issues, and has attracted worldwide interest in recent decades [1].Actually, energy from sunlight that arrives on the earth in 1 h is more than all of the energy consumed by humans in an entire year; thus an affordable future can be certainly achieved if solar energy, the most abundant renewable energy in the earth, is efficiently exploited [2]. However, because of the daily and seasonal variability of sunlight, a cost-effective way in which solar energy can be captured, converted, and stored is highly desired. The most widely recognized method for cost-effective massive energy storage is in the form of chemical bonds. Thus, great attention has been given to the development of highly effective technologies for conversion of solar energy to chemical fuels [3,4].Splitting water into hydrogen and oxygen by using sunlight is a promising approach to solar energy storage [1,4]. Among various technologies, direct photolysis of water upon semiconductors, which was first demonstrated by Fujishima and Honda [5] in 1972, is seen as the best path toward this objective, because it is convenient and cost effective, and has huge potential for further development. Therefore, tremendous efforts have been made during the past 40 years to approach this Holy Grail, that is, solar-driven water splitting [6-10].For realizing solar-driven water splitting, one requires, at the minimum, a light absorber, fuel-forming catalysts, and an electrolyte [11,12]. Among them, the light absorber and the catalysts are the two key components that directly determine the final solar conversion efficiency. Hence, most of the research activities in the field of solar-driven water splitting are centralized on the development of light absorbers and catalysts with high efficiency, long durability, and excellent scalability. Several reviews have comprehensively summarized the current achievements Graphene-based Energy Devices, First Edition. Edited by A. Rashid bin Mohd Yusoff.