High-efficiency oxygen reduction reaction (ORR) catalysts are crucial for facilitating the large-scale exploitation of electrochemical energy storage and conversion technologies. Herein, we demonstrate a carbon-based metal hybrid, which offers a higher electrocatalytic activity than that of the individual composite by optimizing the electronic modulation effect from suitable microstructure. The resulting cobalt@cobalt oxide nanoparticles embedded in N-doped carbon shell couple with hierarchical porous graphene (GCN−Co@CoO), exhibiting a significantly enhanced ORR activity in alkaline solution and highlighting a synergistic effect between N-doped carbon shell and metallic Co species. More precisely, the GCN−Co@CoO hybrid pyrolyzed at 800 °C achieves a more positive half-wave potential of −0.194 V (vs SCE) and superior limiting current of 4.91 mA cm −2 . Moreover, the GCN−Co@CoO composite also shows an outstanding tolerance to methanol crossover effects and long-term stability. Furthermore, based on the GCN− Co@CoO cathode catalyst, the self-assembled microbial fuel cells perform a maximum power density of 611 ± 9 mW m −2 at a high current density of 1869 ± 24 mA m −2 .

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The sluggish kinetic rate-limiting oxygen reduction reaction (ORR) at the cathode remains the foremost issue hindering the commercialization of microbial fuel cells (MFCs). Utilization of the effect of micromolecule conjugation and the synergistic effect between Pd nanoparticles and N-rGO (nitrogen-doped reduced graphene oxide) to stabilize a precious metal onto carbon materials is a promising strategy to design and synthesize highly efficient cathode catalysts. In this study, gallic acid is used to facilitate the coupling of palladium (Pd) with N-rGO to form GN@Pd-GA via a simple hydrothermal process. Notably, the as-synthesized GN@Pd-GA as a cathode catalyst shows an approximately direct four-electron feature and demonstrates a high ORR performance in 0.1 M KOH. Furthermore, the stability and methanol tolerance of GN@Pd-GA are superior to those of the commercial Pt/C catalysts. In addition, a maximum power density of 391.06 ± 0.2 mW m of MFCs equipped with GN@Pd-GA was obtained, which was 96.2% of the power density of MFCs equipped with a commercial Pt/C catalyst.

The mixture Ni0.85Se/Co0.85Se-NHCS-2 displayed superior electrocatalytic performance to that of Ni0.85Se-NHCS or Co0.85Se-NHCS alone. This provided a simple approach to develop ORR/OER bifunctional electrocatalysts for zinc–air batteries.

The high cost, low abundance and poor durability of precious metal catalysts greatly hinder the practical applications of microbial fuel cells (MFCs) for bioremediation and bioelectricity generation. It is imperative to develop highly efficient and robust noble metal-free catalysts for the high power density of MFCs. In this work, we present a scalable and cost-effective strategy to synthesize Co 9 S 8 nanoparticles coupled with nitrogen-doped hollow carbon sphere (NHCS), which subtly constructs synergistic interface structures that expose plentiful active sites and afford high conductive channel for charge transfer. The as-obtained porous Co 9 S 8 /NHCS exhibits excellent catalytic activity, and superior stability as well as methanol tolerance during oxygen reduction reaction (ORR) process in both alkaline and neutral environment. The MFC device equipped with Co 9 S 8 /NHCS as air-cathode achieves a remarkable power density of 704 � 22 mW m À 2 and outstanding chemical oxygen demand (COD) removal rate of 96.28 % � 0.50 %, which is even superior to the performance of commercial Pt/C catalyst. The favorable results provide a new concept to design and explore porous noble metal-free electrocatalysts for clean and sustainable energy conversion.

The efficient and durable oxygen reduction reaction (ORR) catalyst is of great significance to boost power generation and pollutant degradation in microbial fuel cells (MFCs). Although transition metal–nitrogen-codoped carbon materials are an important class of ORR catalysts, copper–nitrogen-codoped carbon is not considered a suitable MFC cathode catalyst due to the insufficient performance and especially instability. Herein, we report a three-dimensional (3D) hierarchical porous copper, nitrogen, and boron codoped carbon (3DHP Cu–N/B–C) catalyst synthesized by the dual template method. The introduced B atom as an electron donor increases the electron density around the Cu–N x active site, which significantly promotes the efficiency of the ORR process and stabilizes the active site by preventing demetallization. Thus, the 3DHP Cu–N/B–C catalyst exhibited excellent ORR performance with the half-wave potential of 0.83 V (vs reversible hydrogen electrode (RHE)) in a 0.1 M KOH electrolyte and 0.68 V (vs RHE) in a 50 mM PBS electrolyte. Meanwhile, 3DHP Cu–N/B–C had satisfactory stability with 94.16% current retention after 24 h of chronoamperometry test, which is better than that of 20% Pt/C. The MFCs using 3DHP Cu–N/B–C not only showed a maximum power density of up to 760.14 ± 19.03 mW m–2 but also operating durability of more than 50 days. Moreover, the 16S rDNA sequencing results presented that the 3DHP Cu–N/B–C catalyst had a positive effect on the microbial community of the MFC with more anaerobic electroactive bacteria in the anode biofilm and fewer aerobic bacteria in the cathode biofilm. This study provides a new approach for the development of Cu-based ORR electrocatalysts as well as guidance for the rational design of high-performance MFCs.

Herein, we present an efficient non‐enzymatic electrochemical sensor for H2O2 detection based on the catalytic‐reduction of H2O2 on ZnMn0.5Co1.5O4. The ZnMn0.5Co1.5O4 derived from ZnCo2O4 by the partial substitution of Co with Mn was synthesized via sol‐gel combustion method. The catalytic performance of ZnMn0.5Co1.5O4 for the reduction of H2O2 is better than that of ZnCo2O4, attributing to the synergetic effects of electronic structure, lattice distortion, and multivalent state of Mn. Specifically, as‐fabricated ZnMn0.5Co1.5O4‐based electrochemical sensor shows an excellent quantitative detection capability toward H2O2 in a wide range of 5 to 7585 μM, with a theoretical detection limit of 0.12 μM (3S/N). Moreover, the excellent reproducibility and selectivity for H2O2 sensing was also verified. The excellent recoveries from 94.4 to 103.2 % were obtained for H2O2‐spiked orange juice and beer. More importantly, the sensor exhibits desirable performance in the real‐time monitoring of H2O2 released from living human colon cancer cell (HCT116 cells). The results indicate that the as‐presented sensor is a promising candidate for the H2O2 determination in food safety and clinical diagnose.