Self-doping active sites in microbe-derived carbonaceous electrocatalysts for the oxygen reduction reaction performance

Microorganisms are rich in heteroatoms,which can be self-doped to form active sites during pyrolysis and loaded on microbederived carbonaceous materials.In recent years,microbe-derived carbonaceous materials,characterized with abundant selfdoping sites,have been continuously developed as cost-effective electrocatalysts for oxygen reduction reaction(ORR).To fully unlock the catalytic potential of microbe-derived carbonaceous materials,a comprehensive analysis of catalytic sites and mechanisms for ORR is essential.This paper provides a summary of the ORR catalytic performance of microbe-derived carbonaceous materials reported to date,with a specific focus on the self-doping sites introduced during their pyrolytic fabrication.It highlights the mono-or co-doping sites involving nonmetallic elements such as oxygen(O),nitrogen(N),phosphorus(P),and sulfur(S)atoms,as well as covers the doping of metallic iron(Fe)atoms with various coordination configurations in microbe-derived carbonaceous materials.Understanding the impact of these self-doping sites on ORR catalytic performance can guide the design of doping sites in microbe-derived carbonaceous materials.This approach has the potential to maximize electrocatalytic activity of microbe-derived carbonaceous materials and contributes to the development of more efficient and cost-effective carbonaceous electrocatalysts.

Visible light induces bacteria to produce superoxide for manganese oxidation

Manganese oxides are widely distributed in soils and sediments, affecting the migration and transformation of heavy metals and organic pollutants. The microbial conversion of soluble Mn(Ⅱ) into insoluble Mn(Ⅲ/Ⅳ) oxides is considered to be the initial source of manganese oxides in the environment;however, whether this process is related to a physiological role remains unclear. Here, we explored the microbial manganese oxidation process under visible light by using coastal surface seawater microorganisms. Visible light greatly promotes the oxidation rate of Mn(Ⅱ), and the average rate reaches 64 μmol/(L·d). The generated manganese oxides were then conducive to Mn(Ⅱ) oxidation, thus the rapid manganese oxidation was the result of the combined action of biotic and abiotic, and biological function accounts for 88 % ± 4 %. Extracellular superoxide produced by microorganisms induced by visible light is the decisive factor for the rapid manganese oxidation in our study. But the production of these superoxides does not require the presence of Mn(Ⅱ) ions, the Mn(Ⅱ) oxidation process was more like an unintentional side reaction, which did not affect the growth of microorganisms. More than 70 % of heterotrophic microorganisms in nature are capable of producing superoxide, based on the oxidizing properties of free radicals, all these bacteria can participate in the geochemical cycle of manganese. What’s more, the superoxide oxidation pathway might be a significant natural source of manganese oxide.

Engineering asymmetric electronic structure of cobalt coordination on CoN_(3)S active sites for high performance oxygen reduction reaction

The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.