High-throughput Screening Study Of Photocatalytic Water Cracking Hydrogen Production Materials Based On In-situ Microbubble Imaging

The excessive exploitation and use of fossil fuels has made h?mans face serious environmental pollution and energy crisis. Therefore, scientists have been studying the focus of replacing non-renewable fossil fuels with clean and renewable energy. Many researchers have found that semiconductor catalytic materials can achieve photocatalytic hydrogen ?H2? production under the inexhaustible sunlight, which can effectively solve the two problems of energy crisis and environmental pollution and has a very important practical significance. Based on these findings, the development of efficient semiconductor catalytic materials has become an important means to improve photocatalytic hydrogen ?H₂? production efficiency. However, single-component photocatalysts cannot be widely used in practical applications because of their relatively wide band gap and limited visible-light absorption. Correspondingly, multicomponent photocatalysts showed a better catalytic performance. Nevertheless, there exist almost inn?merable photocatalysts varying in components and structures. Developing a time-saving and highly efficient screening method has been becoming a very thirsting task. Traditionally, for selecting the photocatalyst researchers often rely on trying according to the pattern "attempt-fail-try again". However, there are so many combinations of photocatalysts that this traditional method for new catalysts exploration always consumes tremendous time and money to obtain some substantial progress. High-throughput screening ?HTS? method has recently emerged as a valuable approach to solve this problem, which can improve the overall efficiency of the testing and screening for new catalytic materials. For this reason, this research will apply high-throughput screening ?HTS? technology to the selection and performance evaluation of catalytic composite materials of hydrogen ?H₂? production, and develop a new HTS method for rapidly screening catalytic materials used in water splitting. The main results are as follows:?1? The glass slides were used as the substrate of micro-reactor chip ?MR-chip? for HTS experiment. Using the properties of negative photoresist and UV lithography ?UVL? technique, the microgrid structure was prepared with the designed size of 500* 500?m on the surface of the glass slide. These prepared hydrophobic grids as reaction units of MR-chip are mutually independent.?2? Using an ultrasonic atomizer, nano-TiO₂ was imported into each reaction unit of MR-chip. It is determined that nano-TiO₂ was well distributed into reaction units under a microscope, which meets the independence of all catalysts in each reaction units. Then, based on the principle of color inkjet printing technology, six kinds of metal ions of modifying nano-TiO₂ were printed into each reaction unit according to the designed different ratios by an inkjet printer. Finally, with sulfide and calcining process, the catalyst library of MSx/TiO₂ was obtained. By XPS characterization, the ratios of six metal sulfides in the prepared catalyst library are consistent with the designed ratios, which satisfied the requirements of HTS catalyst library and had a good foundation for the next HTS experiment.?3? Using CCD imaging principle of micro-bubbles, a new detection method of HTS based on micro bubble imaging ?MBI? was established. Based on the immovable requirement of micro-bubbles in reaction process for the detection method of micro-bubbles imaging ?MBI? in situ, a reaction device ?2D-reactor? suitable for high-throughput screening ?HTS? experiment was developed. The height of the reaction space in this 2D-reactor was designed as 0.5mm. The small space can ensure that micro-bubbles don't move around, which had a certain foundation for the detection method of micro-bubbles imaging ?MBI? and the later position analysis of highly active catalysts..?4? By analyzing the micro-bubble images obtained by HTS experiment, with the bubble size as screening standard of catalytic activity, three catalysts with the highest catalytic activity were selected out. And the three catalyst ratios are (Ni_0.21Zn_0.22Cd_0.25Y_0.01Co_0.05In_0.26)Sx/TiO₂,(Ni_0.27Zn_0.21Cd_0.02Y_0.02Co_0.18In_0.30)SX/TiO₂, (Ni_0.01Zn_0.27Cd_0.25Y_0.31Co_0.06In_0.10) SX/TiO₂, respectively.?5? The selected catalysts by HTS technique were verified by some macro-experiments. The results showed that the efficiency of H₂ production of catalysts with different ratios is consistent with the screening results by our HTS method.