The excessive combustion of fossil fuels leads to large emissions of carbon dioxide (CO2), which exacerbates global climate change. Photocatalytic CO2 reduction is an effective way to solve the above problems, which can use solar energy to convert CO2 into valuable chemical fuels. However, due to the chemical inertness of the CO2 molecule and the high dissociation energy of the C=O bond, the CO2 photoreduction reaction has low reaction efficiency and product selectivity.
In the past few decades, many suitable CO2 photoreduction catalysts have been designed, such as metal-organic frameworks, metal oxides, metal nitrides, metal complexes, covalent organic frameworks, etc. However, their photocatalytic activity and CO2 reduction selectivity are not ideal enough, and further improvement is needed to achieve the goal of practical application.
Based on this,Shen Shaohua, Xi'an Jiaotong UniversityThe research group effectively improved the photocatalytic activity of polymeric carbon nitride (PCN) aerogels by modifying their "integrated" structure. Specifically, crystalline carbon nitride (CCN) self-supporting aerogels with (-CN) functional groups were successfully prepared by molten salt and self-assembly two-step method using polymerized carbon nitride (PCN) as the precursor.
It is worth noting that the increase of CCN crystallinity after treatment improves the charge transfer efficiency, while the multiphoton reflection in the three-dimensional porous structure enhances the light absorption, significantly enhances the mass transfer of reactants and products in the porous structure, and synergistically improves the CO2 photoreduction activity.
The experimental results showed that the prepared CCN aerogel had higher CO2 reducing activity than PCN and CCN, and the CO precipitation rate and CO selectivity were 25., respectively7 mol g 1 h 1 and 938%, and its activity exceeds that of most reported PCN-based photocatalysts. In addition, in-situ spectroscopy and density functional theory (DFT) calculations show that the introduced -CN group with electrons can be used as the active site for CO2 reduction, which thermodynamically reduces the energy barrier of COoh* generation, and increases the CO2 adsorption capacity and hydrophilicity can accelerate the protonation of CO2*, thereby promoting the accumulation of COoh* on CCN aerogels.
In conclusion, through the simultaneous regulation of crystal structure, molecular structure and morphological structure, this study provides an "integrated" strategy for the design of new self-supporting photocatalysts with high efficiency and high selectivity to reduce CO2 emissions.
cayanamide group functionalized crystalline carbon nitride aerogel for efficient co2 photoreduction. advanced functional materials, 2023. doi: 10.1002/adfm.20231263