Fabrication Of Porous Material Interface On Metal Electrode For CO₂ Electrochemical Reduction

The ever-increasing energy demand and severe climate change all over the world motivated the research passion on the sustainable development.There are inestimable scientific prospects for converting CO₂ into carbon-based energy substances.If it were approached with high efficiency,not only greenhouse gases could be controlled,but the human energy crisis could be solved.Among various conversion pathways including thermochemistry,biochemistry,etc.,converting CO₂ by electrochemical methods has attracted the attention of researchers due to the numerous advantages of CO₂ electrochemical reduction.Electrochemical reduction of CO₂ consumes electricity as energy,while electricity belongs to renewable energy which can be obtained from wind energy,solar energy,hydropower,etc.without generating CO₂ again.This is a major advantage of electrochemical catalysis.However,the biggest challenges in electrochemical catalytic carbon dioxide reduction are high energy consumption,low efficiency and stability of the catalyst itself.In this article,we reviewed some of the metal and metal coordination compounds performed as electrochemical catalysts for electrochemical CO₂ reduction reaction?CO₂RR?.The main concept we reviewed was to control the structure of the metal catalyst itself or apply an active site coordinated with metal ions to catalyze CO₂ molecules.We intended to describe a synergistic manner combining the catalytic surface of metal and the specific active cites on organic molecules for the CO₂RR.This concept emphasizes changing the environment of metal surface by ordered porous materials to regulate both selectivity and activity of CO₂RR.Metal-organic frameworks?MOFs?were a kind of newly developed porous materials with various designs.They have various properties such as extremely high surface area,precise adjusted pore diameters and diversification of functional groups providing abundant potential for applications.In this paper,we applied several types of MOFs as examples to explore the construction methods for interfaces between MOFs and substrates or electrodes.In electrochemical catalytic applications,although there weren't outstanding results achieved from the interfaces constructed by MOFs,the growth and interfaces construction of MOFs still provided possibilities for the various applications for MOFs.In addition,a series of porous porphyrin networks?PPNs?films were modified on the surface of the flat Au electrode by in situ electrochemical polymerization,and were successfully applied in the CO₂RR exhibiting high catalytic performance.We have conducted a series of control experiments and characterizations of the PPN and the interface,we found that the amino functionalized PPN has a strong chemical interaction with CO₂ molecules.In parallel,we confirmed that the catalytic sites came from the gold electrode,and the catalytic reaction occurred on the molecularly defined interface between the PPN layer and the Au electrode.Through the discussion of this paper,we concluded the design of concerted catalysis carried out by molecularly defined interface really works and this construct opened up a new pathway for CO₂RR.