Hydrogen vehicles can run 800 kilometers after 3 minutes of hydrogenation with zero emission. With the development and industrialization of hydrogen production technology, it is expected to become a reality. Hydrogen energy, in the context of carbon peaking and carbon neutrality, will become an important energy in the future. How to achieve high-efficiency and low-cost hydrogen production, especially the production of "green hydrogen" by photolysis of water is being researched by many scientists.
At 4 o'clock on Oct. 18, 2022 (Beijing Time), Lian Zichao, a Specially-appointed Professor of the Department of Chemistry, School of Materials and Chemistry of our university, and Institute for Chemical Research, Kyoto University published the research achievements of "Harnessing Infrared Solar Energy with Plasmonic Energy Upconversion" in Nature Sustainability, a top international journal in the field of sustainable green development technology and environmental science. In the research, a new scheme of inducing energy conversion of materials by using undeveloped solar infrared spectrum was provided, which has filled the gap in the field of non-noble metals to achieve efficient plasmon energy upconversion internationally, and means that there is a new practical way to convert water to hydrogen. Lian Zichao is the first author of the paper, and University of Shanghai for Science and Technology is the first unit. This research was supported by the National Natural Science Foundation of China (22109097), Shanghai Natural Science Foundation (20ZR1472000) and Shanghai Pujiang Talents Scheme (20PJ1411800), etc.
Paper Cover
Plasma "Climbing" and "Tracing Light" in the Solar Spectrum
The solar spectrum contains 5% of ultraviolet light, 43% of visible light and 52% of infrared light. Previous researches on photocatalysis have mostly been confined to the ultraviolet and visible lights, while infrared light, which accounts for almost half of the solar energy, is wasted. Can a photocatalyst capable of expanding the response range of the solar spectrum be developed, so as to make the best of solar resources?
With such a doubt, Professor Lian Zichao's team conducted an in-depth research and proposed to use the copper sulphide (CuS) with semimetal-semiconductor properties to construct semiconductor heterojunction, so as to form a good plasma infrared to visible energy upconversion system, thus sharply increasing the utilization of infrared light and realizing the large-scale and affordable application of hydrogen energy.
"When the frequency of incident photon exactly matches the overall vibration frequency of the metal nanoparticles or metal conduction electrons, we can consider it as the photon successfully 'dialing the phone' and being absorbed by oscillation after 'connecting the phone', with very little light scattering. At this time, a stronger resonance-absorption peak appears in the spectrum, and the generated surface plasmon electrons and holes will be transferred to the adjacent wide bandgap semiconductor at the same time." Lian Zichao vividly calls this process "plasma climbing", and he explains that this means that as long as the plasmon in the photocatalyst climbs to the "slope" where local surface plasmon resonance can occur, energy can be enhanced and converted, and infrared energy in solar energy can be converted into visible energy, finally achieving the purpose of improving the utilization rate of infrared light.
Lian Zichao, Specially-appointed Professor
Make Interest Be the "Best Catalyst" from "0.1%" To "5.1%"
In the process of converting water into hydrogen with infrared light, the photocatalytic material is the core, and the activity, stability and cost of the material are the key to determine the application of the photocatalysis technology. "At present, only a few research groups have reported the plasmon upconversion, mainly focusing on GaAs semiconductors modified by electrum, with energy conversion efficiency of 0.1-1%. However, the cost of copper sulfide we use is lower, with the conversion efficiency of 5.1%."
It took five years to complete the research. Then Lian Zichao went to Toyota Technological Institute and Ritsumeikan University in Japan to carry out the related tests of transient absorption spectroscopy. During the test, he, through trying multiple methods, found the phenomenon of efficient plasma hole transfer, and had a preliminary conception for the construction of plasma infrared to visible energy upconversion system. Since there are few people involved in the plasmon upconversion area, the "pioneering way" chosen by Lian Zichao's team was destined to be troubled. With a lot of reasoning on the white board, numerous sets of valid or invalid derived data... finally, his idea was verified through repeated experiments.
Catalyst plays a key role in the conversion system, and Lian Zichao calls interest the best "catalyst" in the research process. "A lot of people think that it is hard and boring to do scientific researches, but I think it is very interesting to find something during research, and the inner joy of achieving phased objectives is beyond words," Lian Zichao said. "A good research, through continuous exploration and mining, should reveal the essence of science." Lian Zichao, with this inquiring spirit, has been engaged in this research for five years. Everything comes to him who waits. Finally, they promoted the efficiency of plasmon energy upconversion to over 5% from infrared light to visible light.
Diagram for Mechanism of Upconversion from Infrared Light To Visible Light Energy
Be a "Pioneer" in the Scientific Research Field Based on National Demands
"Doing scientific research is a process of learning about and exploring nature, but in the end we still have to serve the country and society, so when doing research, we must not 'be oblivious of the outside world'. Research orientation should be based on the frontiers of science and technology in the world and major national demands." This is Lian Zichao's firm scientific research idea.
During his study at Kyoto University, he was determined to return to China for further development and serve the society with what he learned. On Dec. 25th, 2019, Lian Zichao returned to China. Lian Zichao remembered this date very clearly. After returning to China, he officially allied himself to University of Shanghai for Science and Technology and serves as a specially-appointed professor of the School of Materials and Chemistry.
"No achievement can be achieved easily. I think the most important thing is to work hard and focus, with innovative thinking. To overcome difficulties in scientific research, the wisdom of teams is required, and then we should stay dedicated: only by persevering in one direction can we get the reachless 'star' of science." In the research process, of course, I can't do without the substantial support from the University and School. Lian Zichao, as one of the youngest professors of "post-85s generation" in the university, has more prospects for his future research: "I think that we should have our own uniqueness in academic research. If we have chosen our own research field, we should stick to it and make constant research. I hope I can continue to exert myself in my own field and make some innovative achievements, thus becoming a leader and pioneer in this field."
Article linkage:
https://www.nature.com/articles/s41893-022-00975-9
