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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 °C. 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.

Acetylene chemical process, especially catalyzing acetylene acetoxylation for the synthesis of vinyl acetate (VAc), has attracted wide attention in coal-rich countries. Although great efforts have been made to prepare different catalysts to improve the VAc synthesis via acetylene acetoxylation, the acetic acid (HAc) conversion cannot achieve a satisfactory level, much lower than 60%. Herein, ZnO nanoparticles in situ wrapped on zinc-nitrogen-carbon materials (ZnO@ Zn–N–C) have been successfully synthesized. Due to the simultaneous presence of nitrogen and carbon in chitosan, the obtained carbon material achieved in situ nitrogen doping during the high-temperature treatment. Furthermore, the as-obtained ZnO@Zn–N–C exhibits high specific surface area of 1430.1 m2/g and pore volume of 0.92 cm3/g, because Zn composites have the ability to etch carbon to form pores. In particular, ZnO@Zn–N–C displays an amazing catalytic activity for acetylene acetoxylation to synthesize VAc with the HAc conversion high up to 88.8%, which is much higher than those reported in other papers before.

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 half-wave 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. Keywords: Fe/Fe3C nanoparticles, Prussian blue, Microwave, Carbon bath method, Oxygen reduction reaction

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 m2/g than that of 939.5 m2/g from Co-CoO/N-C (CHT), the Co-CoOx/N-C (SBM) performed larger pore diameter and more Co3O4 active component resulting in better ORR performance in 0.1 mol/L KOH solution. The Co-CoOx/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/cm2 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.

Electrocatalysts with strong stability and high electrocatalytic activity have received increasing interest for oxygen reduction reactions (ORRs) in the cathodes of energy storage and conversion devices, such as fuel cells and metal-air batteries. However, there are still several bottleneck problems concerning stability, efficiency, and cost, which prevent the development of ORR catalysts. Herein, we prepared bimetal FeCo alloy nanoparticles wrapped in Nitrogen (N)-doped graphitic carbon, using Co-Fe Prussian blue analogs (Co3[Fe(CN)6]2, Co-Fe PBA) by the microwave-assisted carbon bath method (MW-CBM) as a precursor, followed by dielectric barrier discharge (DBD) plasma treatment. This novel preparation strategy not only possessed a fast synthesis rate by MW-CBM, but also caused an increase in defect sites by DBD plasma treatment. It is believed that the co-existence of Fe/Co-N sites, rich active sites, core-shell structure, and FeCo alloys could jointly enhance the catalytic activity of ORRs. The obtained catalyst exhibited a positive half-wave potential of 0.88 V vs. reversible hydrogen electrode (RHE) and an onset potential of 0.95 V vs. RHE for ORRs. The catalyst showed a higher selectivity and long-term stability than Pt/C towards ORR in alkaline media.