Synthesis And Electrochemical Applications Of Doped Carbon Materials

High-efficiency sustainable energy conversion and storage technologies,such as metal-air batteries,fuel cells,and supercapacitors etc.attract enormous attention due to their clean,efficient,and renewable advantages.At present,the limitation of the scale of the above technology mainly comes from the excessively expensive noble-metal electrode materials.Therefore,the development of cheap and efficient electrode materials is of great importance for the storage and conversion of clean and sustainable energy sources.Carbonaceous materials have attracted much attention due to their wide sources,low price and stable physicochemical properties.However,the electrochemical catalytic performance of carbonaceous materials is not ideal,and often necessary to functionalize heterogeneous elements or materials to endow them with efficient adsorption and catalytic conversion active sites.Based on formamide liquid phase chemistry and organic dehalogenation strategies,the doped carbon materials with intrinsic nonmetallic impurity elements,including N,B,P,S and other elements,which realizes the structure and morphology control of carbon materials on the micro-nano scale,and obtained excellent electrochemical activity,catalytic selectivity and capacitive energy storage specific capacity.The contents are as follows:1.Nitrogen-doped carbon materials with specific carbon defect structure（D-NC950）are constructed through topological transformation of atomic-level dispersed Zn-N₄structure,and their applications in catalytic oxygen reduction reaction（ORR）,and aqueous metal-air battery are developed.The research shows that D-NC950 materials have better ORR catalytic activity,selectivity and stability than Pt/C.At the same time,the Al-air battery assembled with this material shows high specific power(144.0 m W cm^-2)and excellent stability.2.Herein,through an organic dehalogenation strategy,and polyvinylidene chloride（PVDC）as carbon source,coupled with five kinds of organic small molecule doping sources with different relative positions of N and S under mild reaction conditions（strong base,room temperature,ball milling）,five N,S co-doped carbon materials are successfully synthesized,and expecting to obtain the optimal ORR catalytic activity by adjusting the doping structure of N and S.It is found that N,S co-doped carbon（NS-C950）prepared by using thiomorpholine as doping source has better ORR catalytic performance than commercial Pt/C.As the positive electrode of Al-air battery,it shows a specific power of 130.7 m W cm^-2.This work provides a novel strategy for the specific structure doping of multi-doping heterogeneous elements in carbon materials.3.Based on the strategy of organic dehalogenation,we developed a high amount of B-doped carbon materials（up to 5.3 at.%.）which can efficiently promote ORR to produce H₂O₂.The optimal synthesis parameters and selectivity of H₂O₂ were obtained by adjusting the amount of boron source and calcination temperature.The yield of NS-C950 is up to 98%in the three electrode alkaline test system,and the highest yield of H₂O₂is 500 mg g_cat.^-1h^-1 in H-type test cell.4.Through doping carbon materials with a high amount of B（up to 11.5 at.%）and controlling the doping amount of other elements N and P,the specific capacity of the final carbon-doped materials（BNP-C）is improved,the proportion of pseudo-capacitance is increased（the pseudo-capacitance is>40%）,the stable working voltage is broadened（both acid and alkaline voltage windows can use 1.5 V）,and the specific energy(>12.0 Wh kg^-1 under 0.7 kw kg^-1)is improved.What’s more,it has ultra-long cycle stability(only 2%is attenuated after working 5000 times at 50 A g^-1).