Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst

Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking.In this study,ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst.These catalysts were prepared via a one-step method at 900℃.Amazingly,the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles.These facilitated the catalyst synthesis,and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium,including a lower onset potential,lower mid-wave potential,four electron transfer process,and better durability compared with 20 wt%Pt/C.More importantly,the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH*from*OO toward oxygen reduction reaction.Therefore,the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells,given the novel catalyst’s resulting performance.

High efficient oxygen reduction performance of Fe/Fe3C nanoparticles in situ encapsulated in nitrogen-doped carbon via a novel microwave-assisted carbon bath method

Fe-based carbon materials are widely considered promising to replace Pt/C as next-generation electrocatalysts towards oxygen reduction reaction (ORR). However, the preparation of Fe-based carbon materials is still carried out by conventional heating method (CHM). Herein, a novel microwave-assisted carbon bath method (MW-CBM) was proposed, which only took 35 min to synthesize Fe/Fe3C nanoparticles encapsulated in N-doped carbon layers derived from Prussian blue (PB). The catalyst contained large specific surface area and mesoporous structure, abundant Fe-Nx and C–N active sites, unique core-shell structure. Due to the synergistic effects of these features, the as-prepared Fe/Fe3C@NC-2 displayed outstanding ORR activity with onset potential of 0.98 VRHE and halfwave potential of 0.87 VRHE, which were more positive than 20 wt.% Pt/C (0.93 VRHE and 0.82 VRHE). Besides, Fe/Fe3C@NC-2 gave a better stability and methanol tolerance than Pt/C towards ORR in alkaline media, too.

Improved oxygen reduction reaction via a partially oxidized Co-CoO catalyst on N-doped carbon synthesized by a facile sand-bath method

High active and durable non-noble metal electrocatalysts are urgently developed to satisfy the high performance oxygen reduction reaction(ORR). We successfully synthesized Co-CoOx anchored on nitrogen-doped carbon via a facile sand-bath method(SBM), i.e., Co-CoOx/N-C(SBM). The as-obtained Co-CoOx/N-C(SBM) exhibited overwhelming superiorities to Co-CoO/N-C prepared by conventional heat treatment(CHT), particularly in electrochemical performance of ORR. Although Co-CoOx/N-C(SBM)showed smaller specific surface area of 276.8 m^2/g than that of 939.5 m^2/g from Co-CoO/N-C(CHT), the Co-CoOx/N-C(SBM) performed larger pore diameter and more Co_3O_4 active component resulting in better ORR performance in 0.1 mol/L KOH solution. The Co-CoO_x/N-C(SBM) delivered onset potential of 0.91 V vs. RHE, mid-wave potential of 0.85 V vs. RHE and limited current density of 5.46 mA/cm^2 much better than those of the Co-CoO/N-C(CHT). Furthermore, Co-CoOx/N-C(SBM) showed greater stability and better methanol tolerance superior to the commercial 20 wt% Pt/C.

Overwhelming electrochemical oxygen reduction reaction of zinc-nitrogen-carbon from biomass resource chitosan via a facile carbon bath method

Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction(ORR),which is the fundamental for the development and commercialization of renewable energy conversion technology.Herein,zinc-nitrogen-carbon(Zn-N-C)was prepared by using biomass resource chitosan via a facile carbon bath method.The obtained Zn-N-C delivered a high specific surface area(794.7 cm^2/g)together with pore volume(0.49 cm^3/g).During the electrochemical evaluation of oxygen reduction reaction(ORR),Zn-N-C displayed high activity for ORR with an onset pote ntial E0=0.96 VRHE and a half wave potential E1/2=0.86 VRHE,which were more positive than those of the comme rcial 20 wt%Pt/C benchmark catalyst(E0=0.96 VRHE and E1/2=0.81 VRHE).In addition,the ZnN-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.