Improving the electrocatalytic activity of Fe,N co-doped biochar for polysulfide by regulation of N-C and Fe-N-C electronic configurations

The conversion of agricultural residual biomass into biochar as a sulfur host material for Li-S batteries is a promising approach to alleviate the greenhouse effect and realize waste resource reutilization.However,the large-scale application of pristine biochar is hindered by its low electrical conductivity and limited electrocatalytic sites.This paper addressed these challenges via the construction of Fe-N co-doped biochar(Fe-NOPC)through the copyrolysis of sesame seeds shell and ferric sodium ethylenediaminetetraacetic acid(NaFeEDTA).During the synthesis process,NaFeEDTA was used as an extra carbon resource to regulate the chemical environment of N doping,which resulted in the production of high contents of graphitic,pyridinic,and pyrrolic N and Fe-Nx bonds.When the resulting Fe-NOPC was used as a sulfur host,the pyridinic and pyrrolic N would adjust the surface electron structure of biochar to accelerate the electron/ion transport,and the electropositive graphitic N could be combined with sulfur-related species via electrostatic attraction.Fe-Nx could also promote the redox reaction of lithium polysulfides due to the strong Li-N and S-Fe bonds.Benefiting from these advantages,the resultant Fe-NOPC/S cathode with a sulfur loading of 3.8 mg·cm^(-2)delivered an areal capacity of 4.45 mAh·cm^(-2)at 0.1C and retained a capacity of 3.45 mAh·cm^(-2)at 1C.Thus,this cathode material holds enormous potential for achieving energy-dense Li-S batteries.

Heteroatom-doped biochar devised from cellulose for CO_(2) adsorption:a new vision on competitive behavior and interactions of N and S

Biochar,as a potential CO_(2) adsorbent,is of great significance in addressing the problem of global warming.Previous studies have demonstrated that the CO_(2) adsorption performance of biochar can be improved by nitrogen and sulfur doping.Co-doping can integrate the structure and function of two elements.However,the physicochemical interaction of nitrogen and sulfur during doping and the CO_(2) adsorption process remains unclear in co-doped biochar.In this study,the heteroatom-doped biochar was prepared with different additives(urea,sodium thiosulfate,and thiourea)via hydrothermal carbonization,and the physicochemical interaction of nitrogen and sulfur in co-doped biochar was investigated extensively.The findings revealed that nitrogen and sulfur competed for limited doped active sites on the carbon skeleton during the co-doping process.Interestingly,thiourea retained the amino group on the surface of biochar to a great extent due to carbon-sulfur double bond breaking and bonding,which facilitated the formation of pore in the activation process.Significantly,co-doping had no significant improvement effect although nitrogen and sulfur doping separately enhanced the CO_(2) adsorption performance of biochar by 11.9%and 8.5%.The nitrogencontaining and sulfur-containing functional groups in co-doped biochar exhibited mutual inhibition in the process of CO_(2) adsorption.The findings of this study will have pertinent implications in the application of N/S co-doped biochar for CO_(2) adsorption.

One-pot pyrolysis route to Fe−N-Doped carbon nanosheets with outstanding electrochemical performance as cathode materials for microbial fuel cell

The naturally lackadaisical kinetics of oxygen reduction reaction(ORR)in the cathode is one of the important factors that restrict the development of air-cathode microbial fuel cells(MFCs).In this work,the iron-nitrogen-carbon hierarchically nanostructured materials had been successfully fabricated by pyrolyzing glucose,iron chloride,and dicyandiamide with the aim of solving the issue.The obtained catalyst with an ultrathin nanostructure demonstrated an idiosyncratic electrocatalytic activity caused by the high content introduction of nitrogen and iron atoms,large surface area,which will offer sufficient active sites for improving the charge/mass transfer and reducing the diffusion resistance.Furthermore,with the increase of N dopant in the catalyst,better ORR catalytic activity could be achieved.Illustrating the N doping was beneficial to the ORR process.The high content of N,BET surface area caused by the N increasing could be responsible for the superior performance according to results of X-Ray photoelectron spectroscopy(XPS),Raman and Brunner-Emmet-Teller(BET)analysis.The ORR on the Fe-N3/C material follows 4e−pathway,and MFCs equipped with Fe-N3/C catalyst achieved a maximum power density(MPD)of 912 mW/m2,which was 1.1 times of the MPD generated by the commercial Pt/C(830 mW/m2).This research not only provided a feasible way for the fabrication of Pt-free catalyst towards oxygen reduction but also proposed potential cathode catalysts for the development of MFCs.