China makes key breakthrough in greenhydrogen preparation research

Recently, Academician Li Can and ResearcherFan Fengtao from the Dalian Institute of Chemical Physics, Chinese Academy ofSciences (DICP) have integrated a variety of techniques that can be connectedat the spatial and temporal scales, and successfully captured a spatial andtemporal image of the evolution of photogenerated charge transfer ofphotocatalyst nanoparticles. This is the first of its kind in the world, andthe research results were published in the international academic journalNature on October 12.

If the successful "photography"of black holes is a major progress in human cognition of the macroscopicuniverse, the "photography" of the full spatial and temporal imagesis a further step in the observation and utilization of the microscopic world.Just as the giant "Qingming Shanghe Tu" can provide a perspective ofthe urban landscape and the vivid activities of people in Bianjing, the capitalcity of the Northern Song Dynasty, the "photographed" full spatialand temporal images of the evolution of photogenerated charge transfer cangreatly contribute to the understanding of the complex mechanism of energyconversion process.

Why is this discovery so important? Theefficient use of solar energy has long been considered a "holy grail"topic in clean energy research. Solar photocatalytic reactions can decomposewater to produce hydrogen and reduce carbon dioxide to produce solar fuel, andthe resulting hydrogen is truly green hydrogen. In the context of "doublecarbon", the development of green hydrogen is getting more and moreattention. However, this research work, which began in the 1970s, is stillfacing many problems - the reaction process does not seem to be complicated,but the efficiency of solar water decomposition still hovers at a low level ofabout 1.5%. If this efficiency can reach 10%, the cost of green hydrogenproduction can be comparable to the current industrial hydrogen production,breaking through the inefficiency bottleneck is very critical.

"Solar energy is the energy ofeverything growing on the earth, just take one ten thousandth of its energy, itcan solve the sum of all kinds of energy consumed by human every year. Why notput solar energy to use as soon as possible?" Li Chan confessed that themain reason is precisely the low efficiency of utilization. "Once theefficiency problem is solved, it will cause a change in the entire world energypattern."

It is understood that research for thisfield, long-term mostly focused on the application stage, in the most essentialbasic research attention is far from enough. Simply put, the latter is tofigure out why and how the reaction occurs. The reason for this is that thebasic mechanism of the process has been unclear due to the spatial and temporalcomplexity of the separation and transfer of photogenerated charges inphotocatalytic reactions and the participation in chemical reactions, which inturn has constrained the further improvement of catalytic efficiency.

Now, the mystery is finally solved.Academician Li Can and researcher Fengtao Fan have targeted key scientificissues in photocatalysis and studied the dynamic imaging of the solarphotocatalytic charge separation process in the full spatial and temporaldomain, revealing the microscopic process of the complex multiple chargetransfer mechanism and clarifying the essential correlation between the chargeseparation mechanism and the efficiency of photocatalytic decomposition ofwater, providing a new understanding and research strategy for breaking thebottleneck of solar photocatalytic reactions.

According to Can Li, the core scientificchallenge of photocatalytic decomposition of water lies in how to achieveefficient separation and transfer of photogenerated charges. And this processspans huge space-time scales from femtosecond (one trillionth of a second) tosecond and from atom to micron, making it extremely challenging to uncover themicroscopic mechanisms behind it. "Our team has worked forward andbackward to solve this problem for a long time, and by integrating multipleadvanced techniques and theories, we have traced the whole process of theevolution of the separation and transfer of photogenerated charges innanoparticles in the whole domain of space-time."

"By integrating a combination ofmultiple advanced characterization techniques and theoretical simulations, itis like a relay race to track the whole mechanism of electrons and holes tosurface reaction centers in a single photocatalyst particle for the firsttime." Li Can said that the ability to track charge transfer in space-timewill greatly contribute to the understanding of the complex mechanisms in theenergy conversion process, providing new ideas and research methods forrational design of photocatalysts with better performance. "In the future,the results are expected to promote the application of solar photocatalyticdecomposition of water to make solar fuel in real life, providing clean, greenenergy for our production and life."