Biomass Carbon-Supported Iron-Copper-Based Oxygen Reaction Catalyst For High-Efficiency Zinc-Air Batteries

Zinc-air batteries(ZABs)have received much attention for their high energy density,safety and environmentally friendly features.The oxygen reduction reaction(ORR)and oxygen precipitation reaction(OER)occur at the cathode during their charging and discharging process,and the hysteresis kinetics of these two cathode reactions lead to the low efficiency and poor stability of the batteries.Noble metal-based catalysts are still the benchmark catalysts for oxygen reactions,but their high cost is not suitable for large-scale applications.Therefore,the exploration of efficient and inexpensive anode materials is a prerequisite for the development of ZABs.Transition metal compounds exhibit excellent oxygen reactivity,and their compounding with carbon carriers can further improve catalytic activity and stability.When the metal is dispersed and anchored on the carbon carrier,it can form active centers with high surface density and accelerate the oxygen reaction kinetics.Based on this,this thesis aims at preparing efficient electrode materials from cheap biomass,preparing iron-based catalysts with excellent oxygen reaction performance using biomass cellulose and iron salts as precursors,and constructing high-efficiency and long-life hybrid ZABs,investigating the mechanism of action of hybrid batteries using a combination of experimental and in-situ characterization techniques,proposing a new idea of multiple redox pairs coupling strategy to construct hybrid batteries,and broadening the application of carbon-based materials to ZABs.The main studies are as follows:The Fe3O4/Fe2N NPs and N-doped carbon composite catalysts were prepared from cellulose extracted from biomass by graphitization and activation,and the P-modified Fe3O4/Fe2N and N-doped porous carbon composite catalysts(P-Fe3O4/Fe2N@NPC)were further obtained by phosphorylation strategy.The assembly of ZAB with P-Fe3O4/Fe2N@NPC as air cathode has excellent small charging/discharging voltage difference.Using DFT calculations,it was shown that the P modification could modulate the electronic state and coordination environment of Fe,thus reducing the OER reaction potential barrier.Highly dispersed Cu-Fe2P nanoparticles/N,P co-doped carbon composite catalysts were prepared by thermal decomposition strategy using cellulose extracted from biomass and Fe-phytate skeleton as raw materials.The catalysts exhibited an ORR onset potential of 0.99 V,a half-wave potential of 0.86 V and an ultimate current density of 5.7mA cm-2 in alkaline medium.DFT calculations indicated that the synergistic effect between highly dispersed Cu and Fe2P could modulate the electronic structure of the metal,thus reducing the ORR reaction potential.As air cathode,the assembled ZABs have high open-circuit voltage and power density.Composites of Fe dispersed in N,S co-doped carbon(Fe-NSPC)were prepared by complexation of poly pyrrole using cellulose as raw material.The coordination interaction of N in polypyrrole with metal Fe can inhibit the aggregation of metal species at high temperature.As an ORR catalyst,the onset and half-wave potentials were 1.02 and 0.87 V,respectively,and the limiting current density reached 6.0 mA cm-2.The DFT calculations were used to show that the S doping facilitated the reduction of the free energy of OH*desorption,which accelerated the ORR process.A Zn-Cu/Ni/air hybrid battery with an energy efficiency of 79.6%was constructed based on a multiple redox pairs coupling.The in-situ X-ray diffraction spectroscopy combined with quasi-in situ X-ray photoelectron spectroscopy reveals that the reversible conversion of metal ions occurring during the charging and discharging process is the key to improve the efficiency and lifetime of the battery.Based on this,a high-efficiency and long-life Zn-Cu/Co/air hybrid battery was constructed by effectively combining Cu2O@CoV with excellent OER activity and Fe-NSPC catalyst with better ORR activity as the air cathode,which provides a new idea for the breakthrough of ZAB efficiency.The charging and discharging mechanism of the hybrid ZAB was investigated in depth by in situ X-ray diffraction spectroscopy combined with quasi-in situ X-ray photoelectron spectroscopy.The results show that the reversible conversion of Cu-O-Cu?Cu-O and Ni-O?Ni-O-O-H during the charging/discharging process is the key to improve the efficiency and lifetime of the battery.On this basis,high-efficiency and long-life Zn-Cu/Co/air hybrid battery were assembled by combining a highly active OER array electrode(Cu2O@CoV)with a highly active biomass carbon-based ORR catalyst(Fe-NSPC)as an air cathode,and the advantages of the multiple redox pairs coupling strategy in improving the efficiency of the hybrid battery were further explored.And in the study,we found that the hybrid battery can mitigate the corrosion of carbon-based ORR catalysts and improve the lifetime of ZABs assembled with carbon-based materials.