Scalable Preparation Of High Dispersion Metal-nitrogen-carbon Catalysts And Studies Of Their Electrochemical Performance

The development of high-performance electrocatalysts is the key to rapid energy conversion.Although precious metal catalysts have many advantages,their scarcity and high cost limit their large-scale practical application.The atomically dispersed catalyst is not only beneficial to improve the catalytic activity and selectivity of various electrocatalytic reactions,but also can improve the utilization of atoms and reduce costs in large-scale applications.The current methods of synthesizing atomically dispersed catalysts easily lead to the formation of metal clusters and even nanoparticles.Most of the researchers focus on the atomization and precise control of the metal components in the atomically dispersed transition metal nitrogen-carbon（MNC）materials.Therefore,it is still very challenging to develop a low-cost,universal method for its large-scale preparation and application.Based on the principle of physical vapor deposition,this paper has realized the low-cost and controllable mass production of a variety of atomically dispersed single and multi-element metal catalytic materials through the development of atom capture strategies.Afterwards,low-cost activated carbon was used as a carbon matrix material,and a novel method was developed for the large-scale preparation of atomically dispersed MNC materials by using the high nitrogen content of formamide to convert nitrogen to carbon and strong chelation of metal components.Large-scale synthesis strategy-"Glue Strategy",mass synthesis of a series of highly dispersed MNC electrochemical catalysts with industrial value.The main research work is listed as follows:（1）Based on the principle of physical vapor deposition,an atom trapping strategy was developed.Fe atoms are emitted from FeCl₃ in gaseous form at high temperatures,and then captured by defect-rich Zn-NC carriers.Due to the volatilization of metallic zinc,Fe atoms and N atoms are coordinated to form a stable Fe-N_x structure,which inhibits the formation of large particles.The prepared Fe-NC material has a large specific surface area and high nitrogen content,and exhibits better ORR performance than commercial Pt/C.After that,we followed the same idea and synthesized a series of highly dispersed bimetallic catalysts（Fe Co-NC,Fe Ni-NC,Fe Cu-NC,Fe Mn-NC）.Electrochemical tests found that the four catalysts not only have better ORR performance than commercial Pt/C,but also have good OER performance,which is a dual-function electrocatalyst.This work provides new ideas for the synthesis of atomically dispersed catalysts,and also lays a methodological basis for the mass preparation of atomically dispersed catalysts.（2）Based on activated carbon as a carbon matrix material,a novel large-scale synthesis strategy-"glue strategy"was developed by taking advantage of the characteristics of formamide conversion of nitrogen to carbon and strong chelation of metal components.The controllable macroscopic preparation of atomically dispersed Fe-NC catalyst was realized.The study found that Fe-NC material has excellent resistance to methanol poisoning and long-term stability compared to commercial Pt/C.After that,a scale-up experiment was carried out.The test results show that the amplification of production will not affect the catalytic activity of oxygen reduction.This synthesis method is suitable for large-scale production and is expected to promote the design,preparation and actual large-scale application of various low-cost,high-performance new catalysts.（3）Based on the"glue strategy",we used activated carbon to synthesize a series of highly dispersed MNC（M=Co,Ni,Cu,Mn）materials.ORR test shows that Co-NC has the most positive starting potential and half-wave potential,which is comparable to commercial Pt/C.Ni-NC and Cu-NC are used in the electrocatalytic CO₂ reduction reaction.Ni-NC has high catalytic activity,while Cu-NC has serious hydrogen evolution reaction and poor catalytic activity in the entire voltage range.After that,the same method was used to realize the support of highly dispersed Ni-based catalysts（Ni@CeO₂ and Ni@Al₂O₃）on metal oxides.This work will open up a new way for the design of highly dispersed MNC materials with abundant element selection as low-cost and high-efficiency catalysts for ORR,CO₂RR and a variety of liquid and gas phase catalysis.