Climate change caused by human activities has started to affect our environments and natural ecosystems. One important approach to prevent catastrophic consequences and achieve a carbon-neutral society is to develop sustainable energy technologies. For example, currently, the Haber-Bosch process is widely used to fix nitrogen gas to ammonia for the production of fertilisers. In addition, hydrogen is mainly produced by the water gas shift reaction. Both reactions were invented at least a century ago and are involved with high temperature or high pressure conditions. If we can reinvent better catalysts for driving both reactions by either light or electricity at ambient conditions, the energy demand for the reactions will be much less and the reaction conditions will be more environmentally friendly as well.
Therefore, our research group is studying the fundamental mechanisms of those redox reactions that are involved with energy conversion.
Most redox reactions, such as hydrogen-evolving reaction , CO2 reduction reaction and N2 fixation reaction, are involved with multiple electron transfer (ET) and proton transfer (PT) processes. Therefore, understanding how to manipulate ET and PT to obtain the desired products plays a vital role in those reactions involving energy conversion. Based on the kinetic model/analysis developed by us (ACS Catal. 2019, 9,7109-7123. and Phys. Chem. Chem. Phys. 2016, 18, 22364-22372.) recently and operando investigations of a model system (as illustrated in the left figure), we are aiming to understand how to control ET and PT schemes to achieve desired efficiency and selectivity for a given reaction.
The development of semiconductor photoelectrodes and a combination of electrocatalysts with a photoelectrode are another research direction. Particularly, we are aiming to explore how to couple light (i.e. light-harvesting semiconductors) with electrons (i.e. electrocatalysts) to form a photoelectrocatalytic system for promoting a desired redox reaction in the liquid system.
Photoredox catalysis (Photocatalysis)
Recently, collaborating with the Ong group (Angew. Chem. Int. Ed. 2018, 57, 4622-4626.), we have developed a new type of organometallic complexes for photoredox catalysis based on the carbodicarbene (CDC) ligands (as shown in the left figure). We are going to further investigate their unique photophysical and photochemical properties of CDC-based metal complexes and explore more board applications, such as solar cells and photoredox catalysis.
In the past decade, photoredox catalysis becomes an important frontier in organic synthesis. Multiple new concepts, such as the combination of one-electron photoredox catalysis with two-electron transition-metal-catalysed cross-coupling reactions have been demonstrated as a new powerful tool for the strong bond activation. Here, we are exploring other directions on how the confined environment can control the reactivity of photoredox catalysis by studying photoenzymes and comparing them with molecular systems for photoredox catalysis.