CO2 reduction (CDRR) to valuable chemicals and fuels with cost-effective catalysts is a vital part in artificial photosynthesis, which is a promising sustainable energy conversion and utilization technology coupled with reduced CO2 emission.
Due to the low cost and easy functional modification, carbon materials exhibited strong advantages as a CO2 reduction catalyst candidate. However, hydrogen evolution (HER) from aqueous media possessed strong competition with CO2reduction. Current solutions involve nitrogen and boron doping to suppress the HER and improve the CDRR activity and selectivity, while these catalysts still show a gap with state-of-art noble metal catalysts.
In a recent study published in Angewandte Chemie International Edition, the research group led by Prof. WANG Yaobing at Fujian Institute of Research on the Structure of Matter of Chinese Academy of Sciences reported an efficient metal-free fluorine-doped carbon (FC) electrocatalyst for selective CO2 reduction.
This study represented an unprecedented 250,000 times enhancement of CO2 reduction activity on FC catalyst compared to non-doped catalyst. The HER activity was only ~20% of the non-doped catalyst. The highlight of this new doping strategy was the fluorine doping tuning the electron structure of the carbon atoms far from several bonds.
Researchers achieved the fluorine doping by a facial pyrolysis of commercial BP2000 and polytetrafluoroethylene with only ~0.3% fluorine content, which was much lower than nitrogen and boron doping (~5%). The obtained fluorine doped carbon (FC) showed 1.5 times enlarged electrochemical active surface compared to the non-doped carbon.
They found that the strong electronegativity of fluorine affect long-rang carbon atoms, activating them to be CDRR active sites and suppress their HER activity by stabilizing the CDRR key intermediate COOH*, and inhibiting the desorption of HER key intermediate H*. Thus, the inherent CDRR activity of FC was dramatically enhanced compared to the 1.5 times increased quantity of active sites, leading to 250,000 times enhancement of CO2 reduction activity on FC.
The electrochemical CO2 splitting cell equipped with FC catalyst as cathode could achieved 68% energy efficiency. When further coupled with a commercial solar cell, the hybrid device can convert solar energy to fuels with the energy efficiency of 13.6%.
The results proposed a new metal-free fluorine doped carbon catalysts and a novel doping mechanism for CO2 reduction, which could promote the development of cost-effective artificial photosynthesis.
Figure: The paper was highlight in the inside cover of the journal, fluorine doping enhances metal-free carbon catalysts towards CO2 reduction. (Image by Prof. WANG’s group)
Contact:
Prof. WANG Yaobing
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Email: wangyb@fjirsm.ac.cn
