【Frontiers in Chemical Technology】35-year-old Chinese scientist increases efficiency of converting CO2 to ethylene to 60%

Since both the redox potentials for the reduction of cuprous oxide to copper and its oxidation to copper oxide lie within the band gap, the photo-etching reaction of cuprous oxide proceeds more easily under light. However, the mechanism of photo-corrosion in copper oxide photocathodes has not yet been fully understood. In-depth research on this topic could enable the development of appropriate protection strategies for similar unstable materials, thereby addressing the issue of material stability. In the past, Liu Guiji and his team have been working on solar energy conversion; they aim to transform carbon dioxide into usable chemicals or fuels through carbon dioxide reduction, utilizing sunlight in the process and involving semiconductor materials. As mentioned earlier, most semiconductor materials such as cuprous oxide are unstable under reducing conditions. Yet almost no one studies the reasons for instability or how to apply it under appropriate conditions. Meanwhile, the chemical transformations that occur in metal oxides under working conditions limit their application in artificial photosynthesis. Therefore, understanding these chemical changes is a prerequisite for achieving the sustainable production of solar fuels and chemicals. In this study, what Liu Guiji set out to address was precisely this long-standing problem.

Protection strategies are provided to mitigate the degradation of electrode performance. Under the relevant reaction conditions, Liu Guiji explained the changes in copper oxide photoelectrodes, which enables the development of protection strategies to reduce the degradation of electrode performance. Under illumination, in agreement with theoretical predictions, he found that copper oxide in the material undergoes both photoelectron reduction and hole oxidation processes, and that the rate of its performance degradation is related to the presence of an electrolyte. Based on a deep understanding of the mechanism, Liu Guiji designed a protection scheme: using a silver catalyst to accelerate the transfer of photo-generated electrons, and a Z-shaped heterojunction to capture holes. The results show that during carbon dioxide reduction, the photocathode exhibits a stable photocurrent for several hours; the Faradaic efficiency of ethylene conversion is approximately 60% and remains stable over several hours, whereas the bare cuprous oxide begins to show performance degradation within a few minutes. Subsequently, Liu Guiji also demonstrated the following principle: by integrating cuprous oxide into heterojunctions and adjusting the utilization efficiency of carriers, it is possible to use cuprous oxide photocathodes in non-aqueous solutions for the selective and sustainable reduction of CO₂ to ethylene. @The wise are enlightened @Cleaner @BookBoy @RedLee_ZZHI @654262293 @CentralPlainsMan @Nuts

It took over two years to achieve a breakthrough in technology. During the research, Liu Guiji first had to test the materials, and in that process he discovered a close relationship between the materials and the solutions. It is generally believed that a solution is a supporting condition that does not affect the properties of the material itself. But he found that there is an important connection between the material and the solution. Thus, he began to conduct chemical spectroscopy and various types of characterization, and compared the changes before and after. Through in-situ testing, he directly observed the changes in the material under lighting conditions, that is, in its operating state. The so-called in-situ experiment refers to observing the changes that occur simultaneously as a reaction takes place, allowing one to see the process by which things change. But sometimes its change does not occur at the beginning and end, but in the intermediate states. In this process, Liu Guiji needs to observe the changes that occur when the reaction takes place, as it is possible that after the object is removed from the reaction conditions, it returns to another state. Through these characterization tests, he learned about the process of material corrosion and deterioration. Subsequently, he identified several key factors; by suppressing these factors, he devised corresponding solutions and protected it through modifications in order to extend its service life. It is generally believed that material corrosion is related to the properties of the material itself, especially in the case of photo-corrosion. Therefore, during testing, solid materials are placed in a liquid for testing. However, as a supporting electrolyte, the effect of liquid solutions is generally not considered, and it is merely tested under normal conditions. However, this material is solid when it is made, and the moment it is placed in a solution, an unexpected reaction occurs, which causes it to corrode very rapidly. This additional factor, which had not been recognized before, was gradually uncovered only after he conducted thorough comparisons and experiments.

Discussion is welcome; if this technology is implemented, it will be revolutionary

It’s a pity that the achievements were still realized in the United States

I’m not sure whether this technology has been industrialized yet

Not yet; it’s just basic research in the laboratory, there is only a possibility