Unknown! Chinese scientists reveal the "magic magic" of solar photocatalytic hydrogen production

Solar photocatalytic reactions can split water to produce hydrogen and reduce carbon dioxide to produce "solar fuel". How the magical "magic" of sunlight is realized has always been a difficult problem in the field of science. Recently, good news came from the Chinese Academy of Sciences: the research team led by academician Li Can and researcher Fan Fengtao of Dalian Institute of Chemical Physics, Chinese Academy of Sciences (hereinafter referred to as "Dalian Institute of Chemical Physics") successfully uncovered this mystery and "photographed" the photogenerated charge Transfer evolution full space-time imagery. Relevant research results were published in the international academic journal "Nature" on October 12.

The core scientific challenge of photocatalytic water splitting lies in how to achieve efficient separation and transport of photogenerated charges. "In the process of photocatalysis, photogenerated electrons and holes need to be separated from the interior of micro-nano particles and transferred to the surface of the catalyst to start the chemical reaction." Fan Fengtao introduced that since this process spans from femtoseconds to seconds, from atoms to microns Unraveling the microscopic mechanism of this process is extremely challenging.

"For a long time, our team has been working on solving this problem. In this work, integrating a variety of advanced technologies and theories, we tracked the whole process of separation and transfer evolution of photogenerated charges in nanoparticles in the whole space-time domain. "Li Can said.

According to Li Can, by integrating a variety of advanced characterization techniques and theoretical simulations, including time-resolved photoemission electron microscopy (femtoseconds to nanoseconds), transient surface photovoltage spectroscopy (nanoseconds to microseconds) and surface photovoltage microscopy (microseconds) second to second), etc., like a relay race, for the first time in a photocatalyst particle to track the entire mechanism of electrons and holes reaching the surface reaction center.

The ability to track charge transfer in time and space will greatly promote the understanding of complex mechanisms in the energy conversion process, and provide new ideas and research methods for the rational design of photocatalysts with better performance. "In the future, this achievement is expected to promote the application of solar photocatalytic water splitting to produce 'solar fuel' in real life, gradually turning dreams into reality and providing clean and green energy for our production and life," Li Can said.

There are three typical technical routes for solar water splitting to produce hydrogen, namely photovoltaic assisted electrolysis of water, photocatalytic water splitting and photocatalytic water splitting. Among them, photovoltaic assisted electrolysis of water, that is, the use of green electricity generated by photovoltaics to electrolyze water to produce green hydrogen.

It is the simplest and most economical to use photocatalysts to realize solar water splitting to produce hydrogen. The device construction is easier, the overall cost is cheap, and it is easy to scale up. This technology began in 1972 when two professors, Fujishima A and Honda K from the University of Tokyo reported for the first time that TiO2 single crystal electrodes photocatalytically decompose water and generate hydrogen, thus revealing the possibility of using solar energy to directly decompose water to produce hydrogen Possibility, opened up the research path of hydrogen production by photolysis of water using solar energy. Photocatalysts currently entering the field of vision of scientists include tantalates, niobates, titanates, and polysulfides.

In addition to the search for catalysts, how to achieve efficient separation and transport of photogenerated charges is also an important part. The discovery of Dalian Institute of Chemical Physics has a huge role in promoting photocatalytic hydrogen production.