Development of hydrogen energy and environment

From primitive wood to nowadays fossil fuels such as coal, oil and natural gas, it can be seen that the forms of energy becomes more and more diverse and the core trend of decarburization is also obvious （the rate of the element of H to C ranging from 1/10, 1/2-1, 2, to 4 in wood, coal, oil and natural gas, respectively）. Although the content of C in current main fuels becomes less and less, the excess exploitation and extensive utilization of various fossil fuels are widely recognized to be responsible for the deterioration of the environment （greenhouse effect, acid rain, photochemical pollution, etc.）. With the roar consumption of energy to maintain the development of human society and taking the environmental problems into consideration, it is inevitable to develop renewable energy containing more H and less C as possible. Under these circumstances, the development of H2 energy is the certain and ultimate choice for its high energy per unit, diversity resources, no pollution to environment and ideal renewable utilization cycle. There are so many methods and ways were employed to develop HE energy, such as electrolysis, methane stream reforming process, coal gasification, etc., but there lies two main problems in current methods and ways, those are the cost of bulk of first energy to extract HE from fossil raw materials and still facing the problems of C deposition （carbon dioxide）. Consequently, if considering the cost and environmental issues, the development of HE energy must resort to renewable energy sources such as solar energy, wind energy to extract HE from water. Based on this context, the development of HE energy by semiconductor photocatalyst to split water into HE and O2 under the irradiation of solar energy, photocatalysis process in short word, is one of the most promising ways. In this review, the importance and necessity to develop hydrogen energy were intensively studied based on the relationship between energy consumption and environment effect. Then the current ways and methods to develop hydrogen were reviewed, especially the state-of-the-art photocatalysis process （from the semiconductor photocatalyst materials perspective）.

Development of hydrogen energy and environment