Construction Of Carbon-based Non-noble Metal Electrocatalyst And Their Oxygen Reduction Reaction Performance

Oxygen reduction reaction（ORR）plays an important role in energy storage and conversion technology（such as fuel cells and metal-air batteries）.At present,precious metal Pt-based materials are the most effective electrocatalysts for ORR,but their scarce reserves and high price significantly increase the overall cost of fuel cells and metal-air batteries,thus limiting their large-scale application.Transition metal（TM=Fe,Co,Ni,Mn,etc.）catalysts have attracted much attention due to their abundance and adjustable catalytic activity.High performance non-precious metal（NPM）ORR electrocatalysts are promising alternatives to Pt-based electrocatalysts.In this paper,carbon-based NPM electrocatalyst is taken as the research object,and non-precious metal monatomic electrocatalyst（NPM SACs）with excellent ORR activity and stability is prepared by the synthesis strategy of wet chemisorption and high temperature pyrolytic carbonization.The main research contents are as follows:1.Fe single-atom electrocatalysts anchored by porous carbon spheresBy anchoring N and S diheteroatoms and metallic Fe atom precursors on the defect sites of porous carbon spheres,the N and S co-doped porous carbon spheres based Fe single-atom electrocatalysts（Fe-SAs@N/S-PCSs）have been prepared.At a low catalyst load(0.255 mg cm^-2),the prepared Fe-SAs@N/S-PCSs showed outstanding performance,with an E_onset of 1.02 V and a half-wave potential(E_1/2)of 0.90 V in 0.1 M KOH solution.It was higher than Pt-based electrocatalysts(E_onset=1.01 V,E_1/2=0.86V),and showed good OER activity(10 m A cm^-2,450 m V).The porous structure and abundant active sites enable the prepared Fe-SAs@N/S-PCSs catalyst to have excellent ORR activity and durability.In addition,the zinc-air batteries assembled with Fe-SAs@N/S-PCSs as the cathode material has large open-circuit voltage,high power density and small voltage gap.2.Construction of Fe single-atom electrocatalyst assisted by organic ligandsHigh activity Fe single-atom electrocatalyst（SA-Fe-N-CNTs）was synthesized by constructing a composite of metal-organic ligand and carbon nanotubes during high temperature pyrolysis.SA-Fe-N-CNTs had a large E_onset（1.02 V）and E_1/2（0.90 V）.The activity and stability of SA-Fe-N-CNTs were superior to those of commercial Pt/C(E_onset=1.00 V,E_1/2=0.86 V)at the same load.The synthesis strategy developed by us has certain universality and can be applied to other transition metal（TM）catalysts（SA-Co-N-CNTs,SA-Ni-N-CNTs,SA-Mn-N-CNTs）.In addition,liquid and flexible zinc-air batteries assembled with SA-Fe-N-CNTs as air cathodic cells showed excellent open-circuit voltage,power density and charge/discharge cycle stability.