The Preparation And Electrocatalytic Performance Of Transition Metal And Carbon-based Composites Electrocatalysts

The excessive use of fossil fuels has caused serious environmental problems.Developing clean and sustainable energy conversion and storage devices is urgent.Metal-air batteries have attracted widespread research interest due to its extremely high theoretical energy density,low cost,rich resources,environmental friendliness,and high safety.The oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?are two crucial half-reactions on the air cathode in metal-air batteries;however,the sluggish kinetics severely limited their commercialization.Therefore,it is essential yet challenging to develop high activity,conductivity and stability bifunctional catalysts.In this paper,three transition metal decorated carbon-based composites electrocatalysts were successfully synthesized by using different precursors.The morphology,structure and composition of resultant catalyst were explored by various characterization techniques.The contents of this paper are as follows:?1?Synthesis of Graphene-encapsulated cobalt nanoparticles embedded in porous nitrogen-doped graphitic carbon nanosheets as efficient electrocatalysts for oxygen reduction reactionHerein,a facile efficient pyrolysis approach was developed to prepare graphene-encapsulated Co nanoparticles?NPs?embedded in porous nitrogen doped graphitic carbon nanosheets?Co@G/N-GCNs?,in which g-C₃N₄ served as C and N sources,and cobalt phthalocyanine?CoPc?as the Co-and N-sources.The as-obtained catalyst exhibited exceptional ORR activity(E_1/2=0.86 V),good durability(12 mV negative shift of E_1/2 after 2000 cycles),and strong methanol resistance,surpassing those of commercial Pt/C catalyst in alkaline conditions.The pyrolysis temperature had critical impacts on the ORR features.This work offers a feasible strategy for exploiting cost-effectiveness non-noble-metal catalysts for energy conversion and storage.?2?Formation of ultrafine NiCoP-decorated N,S,P-codoped hierarchical porous carbon nanosheets as an efficient bifunctional electrocatalyst for oxygen reduction and oxygen evolutionIn this work,ultrafine NiCoP nanoparticles decorated on N,S,P-codoped hierarchical porous carbon nanosheets?NiCoP/NSP-HPCNS?were fabricated via a simple yet effective pyrolysis strategy.Herein,thiourea and phytic acid?PA?served as S and P sources,cobalt acetate?CA?and nickel phthalocyanine?NiPc?as the metal,C and N precursors.The NiCoP/NSP-HPCNS displayed extraordinary enhancement in ORR,with a half-wave potential of 0.84 V and enhanced limiting current density of 6mA cm^–2 in 0.1 M KOH,outperforming commercial Pt/C(0.84 V and 5.1 mA cm^–2).Furthermore,the catalyst exhibited outstanding catalytic property for oxygen evolution reaction?OER?,with a low overpotential of 299 mV at the current density of 10 mA cm^–2 in 1 M KOH.This work opens up a new avenue to prepare highly effective,low cost and bifunctional electrocatalysts for sustainable energy applications.?3?Bio-inspired one-step pyrolysis fabrication of 3D porous Co,N,P-doped carbon nanosheets as high-efficient bifunctional oxygen electrocatalyst for rechargeable Zn-air batteryHerein,a one-step pyrolysis method was developed to prepare Co,N,P-doped porous carbon nanosheets?Co,N,P-PCNS?with abundant CoN_x active sties,using vitamin B12?VB12?as the Co and P sources and g-C₃N₄ as the C and N precursor.The Co,N,P-PCNS exhibited prominent ORR activity(E_1/2=0.87 V)superior to Pt/C(E_1/2=0.84 V)in 0.1 M KOH electrolyte,coupled with a low overpotential?319mV?for OER at 10 mA cm^–2 in 1.0 M KOH electrolyte.Strikingly,the assembled rechargeable Zn-air battery delivered remarkable peak power density of 101.3 mW cm^–2 at a potential of 0.71 V.This work offers impetus for rational fabrication of cost-effectiveness and highly active bifunctional oxygen electrocatalysts for energy transportation and storage.