With the rapid socio-economic development taking place in China, the excessive consumption of fossil fuels has resulted in a large amount of carbon dioxide emissions, leading to a global energy and environmental crisis.

To solve this problem, chemical engineering scientists have committed to use of solar energy and semiconductor photocatalysts, with a view to developing "artificial photosynthesis”. By transformation of the carbon dioxide and water into hydrocarbons or hydrogen, the carbon cycle can be realized and new energy development and utilization can occur.

Over the years, Professor Gong Jinlong of the School of Chemical Engineering and Technology at Tianjin University, with the support of the National Natural Science Foundation of China, has improved the efficiency of artificial photosynthesis by modifying and improving the catalyst.

Innovation of a scientific principle

The promotion of electron-hole separation and transport in the catalyst and the improvement of the carrier reaction rate on the catalyst surface have become important research targets in the artificial light synthesis field.

"We want to efficiently stimulate the formation of electrons which would selectivity participate in the water or carbon dioxide reduction reaction, while the particular nanostructure of the catalyst helps increase occurrence of the reduction reaction, thus realizing the efficient conversion of solar energy to hydrogen and hydrocarbon fuel," Gong Jinlong told the China Science Daily reporter.

With the efficient use of electrons and holes generated by excitation semiconductor materials as the main idea, Gong led his research team in the design and preparation of the catalyst system.

A new method of creating photocatalytic water

Based on innovative application of scientific principles, Gong’s group achieved progress in the design and preparation of photocatalytic water hydrogen catalysts.

Through promotion of separation and conduction of photo-generated carriers, suppression of electron-hole recombination becomes an effective means of improving carrier utilization efficiency. Meanwhile, through nano-porous material design and preparation, shortening the path of photo-generated carriers can effectively inhibit electron-hole recombination.

Zhang Jijie, a doctoral student from Gong’s team, successfully prepared a series of bismuth binary oxide anodic semiconductors by the anion exchange method under solvothermal conditions. At the same time, another doctoral student from the team, Li Ang, designed a hollow sphere structure constructed through TiO2 - In2O3 thin heterostructures which had more than twice the speed of the traditional titanium dioxide catalyst. Another effect was to increase the rate of photogenerated carriers on the surface of the catalyst. PhD students Chang Xiaoxia and Li Ang improved the efficiency of electron and hole separation, and also increased the surface oxygen reaction rate.

Enhance the efficiency of carbon dioxide reduction

Researchers also studied the surface of the water decomposition reaction path and mechanism. They designed a "double-promoter" system for the two-step reaction of oxygen-generated water to produce oxygen. At the same time, Chang Xiaoxia introduced a system for carbon dioxide reduction reaction in aqueous solution, and the researchers directed the reaction path of the electrons on the surface of the catalyst in response to the serious problem of hydrogen production side reaction in the aqueous solution.

Gong said that over the years, the research team has made some progress in the artificial light synthesis field with the support of the National Natural Science Foundation and the national key research project. However, due to the complexity of the reaction process, many mechanisms still need further analysis. In the future, they will try to reveal the microscopic mechanisms of artificial photosynthesis from microcosmic and dynamic perspectives, and further guide the efficient synthesis of photocatalysts to realize the efficient conversion of light energy to chemical energy.