At 4:00 p.m.On October 18, 2022, Beijing time, Professor Zichao Lian, Distinguished Professor of the Department of Chemistry, School of Materials and Chemistry, and the Institute of Chemistry, Kyoto University published a paper on“Harnessing infrared solar energy with plasmonic energy upconversion” in “Nature Sustainability”, a top international journal in the field of green sustainable technology and environmental science. The research provides a new solution to induce energy conversion in materials by using unexplored infrared light region of solar energy, filling the gap in the field of efficient plasmonic energy upconversion of non-precious metals in the world, which means that there is a new practical path for “water to change into hydrogen”. Zichao Lian is the first author of the paper and the University of Shanghai for Science and Technology is the first unit of the paper. The research gets support from such projects as the National Natural Science Foundation of China (22109097), Shanghai Natural Foundation of China (20ZR1472000), and Shanghai Pujiang Talent Program (20PJ1411800).
Plasma “climbing” “chasing light”in the solar spectrum
The solar spectrum contains 5% of ultraviolet light, 43% of visible light and 52% of infrared light. Previous research on photocatalysis has mostly been limited to the ultraviolet and visible range, while infrared light, which accounts for almost half of solar energy, has been wasted. Is it possible for mankind to develop photocatalysts to expand the response range of the solar spectrum and accordingly make full use of solar light resources?
With such a question, Prof. Zichao Lian’s team has conducted an in-depth study and creatively proposed the use of copper sulfide (CuS), a semi-metallic-semiconductor in nature, to construct semiconductor heterojunctions to form a good plasma infrared-to-visible energy upconversion system, which significantly improves the utilization of infrared light and makes the large-scale and affordable application of hydrogen energy possible.
“When the incident photon frequency matches the overall vibration frequency of the metal nanoparticles or metal conduction electrons exactly, we can assume that the photons have succeeded in 'dialing the phone' and are absorbed by the oscillation 'on the phone', but only a very small portion of light is scattered, at which point a strong resonant absorption peak appears on the spectrum, and the resulting surface equipartition exciton electrons and holes are simultaneously transferred to the top of the adjacent broad-band semiconductor.” This process, which Zichao Lian graphically refers to as “plasma climbing,” means that the plasma excitations in the photocatalyst simply climb up the “hill” where the local surface plasmon resonance occurs, and then the energy is enhanced and converted, converting the solar energy from infrared to visible. This means that by climbing the “slope” of the photocatalyst to the point where local surface plasmon resonance occurs, the energy enhancement and conversion can be achieved, converting infrared light energy from solar energy to visible light energy, and ultimately increasing the utilization of infrared light.
Professor Zichao Lian, Distinguished Professor of the Department of Chemistry, School of Materials and Chemistry
From “0.1%” to “5.1%” . Let interest be the best “catalyst”!
In the process of making use of infrared light to “change water into hydrogen”, photocatalytic materials are the core factor, while the activity, stability and cost of the materials are the keys to determine whether photocatalytic technology can be applied in practice. “Only a very few teams have reported on the conversion of iso-excited elements, mainly in GaAs semiconductors modified with gold and silver alloys, with energy conversion efficiency of 0.1-1%. And we make use of copper sulfide at a much lower cost, with a conversion efficiency of up to 5.1%.”
as long as five years, and Zichao Lian travelled abroad many a time in the world, like to Toyota Institute of Technology and Ritsumeikan University in Japan to do tests related to transient absorption spectroscopy. During the tests, he tried a variety of possible methods and discovered the transfer phenomenon of high-efficiency plasma cavities, which led to a preliminary idea for the construction of a plasma infrared to visible energy upconversion system. Since few people have been involved in the field of plasma upconversion, the pioneering path chosen by Zichao Lian's team was bound to be a very difficult one. A whiteboard of reasoning, countless sets of valid and invalid derived data ...validated his idea in repeated experiments at long last.
Catalysts play an important role in the conversion system, and Lian Zichao calls his interest the best “catalyst” in the research process. “Many people think that research is incredibly hard and extremely boring, but I think it is very interesting to make discoveries in the research process, and the joy I feel when I have achieved periodical results is beyond words,” says Zichao Lian, “A good research job is one that goes through constant and continuous exploration and digging to reveal the essence of science.” It is with this spirit of in-depth research that Lian Zichao has been working on this study for five solid years. Just as the old saying goes, “Where there's a will, there's a way.” Lian and his team have eventually pushed the conversion efficiency from infrared light to visible light to more than 5% on the energy of the equipartition excitations.
To be a “pioneer” in scientific research to meet the demands of the nation
“Scientific research is a process of understanding nature and exploring nature, but ultimately we have to serve the country and society, so we must not 'turn a deaf ear to things outside the window' when doing research, and the direction of research should be oriented to the world's scientific and technological frontiers and urgent needs of the nation.” This is the research philosophy that Zichao Lian has never wavered from.When he was still studying at Kyoto University, he was determined to return to China and use what he had learned to serve society. December 25, 2019 is a date Lian Zichao remembers well--the very day he returned to China. After his return, he joined USST as a Distinguished Professor in the School of Materials and Chemistry.
“No achievement can be obtained with ease, I think what counts most are still concentration and persistence, plus innovative thinking. To overcome difficulties in scientific research, the first thing we need is team wisdom, and then we need to stay focused: only by persevering in one direction can we pick the seemingly unreachable 'star' in science. Of course, we could not have succeeded in our research without the strong support from USST and SMC.” As one of the youngest “post-1985” young professors in the university, Zichao Lian has more prospects for his future scientific research journey: “I think academic research should have its own unique features, so once I have chosen my own research field, I will persevere and explore it relentlessly. I hope to make some innovative achievements in my field and strive to become a leading figure and a pioneer in the field.”