Application Of Transition Metal Materials In Zinc-air Batteries And Water Splitting

New energy technology is of great significance to conquer the current energy crisis and environmental pollution.Among them,fuel cell（FC）and electrochemical catalyzing water splitting（WS）technology provide a cost-effective,high-efficiency and environmentally friendly pathway for energy conversion and storage.Three important electrocatalytic reactions are involved:hydrogen evolution reaction（HER）,oxygen evolution reaction（OER）,and oxygen reduction reaction（ORR）.At present,however,the currently required high-activity catalysts are mainly composed of exorbitant and scarce metals such as platinum,ruthenium,and iridium,which have poor stability and cannot meet the needs of large-scale production,manufacturing,and utilization.Therefore,non-noble metal catalysts with low-cost,high activity and high stability can be developed by rationally designing catalysts components,optimizing of pore structure and regulating of electronic structure.In view of the above points,this paper mainly does the following work:（1）A facile and reliable route to convert ZIF-8 modified by Fe-phenanthroline into iron incorporated and nitrogen doped carbon dodecahedron nanoarchitecture（Fe-NCDNA）,in which carbon nanosheets are in-situ formed as the building block with uniform Fe-N-C species decoration.As synthesized electrocatalyst possess highly attractive catalytic features toward ORR in terms of activity and durability in both alkaline and neutral medium,showing excellent catalytic activity and stability.The zinc-air battery with the optimal material as cathode catalyst performs a power density of 184 m W cm^-2 and a specific capacity of 801 m Ah g^-1,suggesting the great competitiveness in terms of activity and durability over the Zn-air device with Pt-based cathode electrocatalyst.（2）N and S co-doped carbon clad bimetal phosphates were prepared by introducing nitrogen source and sulfur source compound cross-linking in one-pot pyrolysis.Electrochemical tests exhibit that the prepared materials have high catalytic properties for ORR,OER under alkaline conditions and HER in acidic solutions.Advanced catalytic activity enables the material to be applied in zinc-air batteries and asymmetric electrolyte cells.The optimized catalyst is equipped in an alkaline zinc-air battery,the battery demonstrates superior performance exceeds commercial materials,with a maximum power density of 205 m W cm^-2 and a stable operation for 1500cycles.The asymmetric electrolyte electrolyzed water device is built at the same time and provides a voltage about 1.0 V at a current density of 10 m A cm^-2,which is far lower than the 1.68 V of the alkaline electrolyzed water device,and significantly improves the current density of electrolysis water.