Preparation and Application of Fe-N Co-Doped GNR@CNT Cathode Oxygen Reduction Reaction Catalyst in Microbial Fuel Cells

Synthesis of Fe-N doped porous carbon/silicate composites regulated by minerals in coal gasification fine slag for synergistic electrocatalytic treatment of phenolic wastewater

Coal gasification fine slag (CGFS), as a difficult-to-dispose solid waste in the coal chemical industry, consists of minerals and residual carbon. Due to the aggregate structure of minerals blocking pores and encapsulating active substances, the high-value utilization of CGFS still remains a challenge. Based on the intrinsic characteristics of CGFS, this study synthesized Fe-N doped porous carbon/silicate composites (Fe-NC) by alkali activation and pyrolysis for electrocatalytic degradation of phenolic wastewater. Meanwhile, minerals were utilized to regulate the surface chemical and pore structure, turning their disadvantages into advantages, which caused a sharp increase in m-cresol mineralization. The positive effect of minerals on composite properties was investigated by characterization techniques, electrochemical analyses and density functional theory (DFT) calculations. It was found that the mesoporous structure of the mineral-regulated composites was further developed, with more carbon defects and reactive substances on its surface. Most importantly, silicate mediated iron conversion through strong interaction with H2O2, high work function gradient with electroactive iron, and excellent superoxide radical (•O2-) production capacity. It effectively improved the reversibility and kinetics of the entire electrocatalytic reaction. Within the Fe-NC311 electrocatalytic system, the m-cresol removal rate reached 99.55 ± 1.24%, surpassing most reported Fe-N-doped electrocatalysts. In addition, the adsorption and electrooxidation experiment confirmed that the synergistic effect of Fe-N doped porous carbon and silicate simultaneously promoted the capture of pollutants and the transformation of electroactive molecules, and hence effectively shortened the diffusion path of short-lived radicals, which was further supported by molecular dynamics simulation. Therefore, this research provides new insights into the problem of mineral limitations and opens an innovative approach for CGFS recycling and environmental remediation.

Synergistic advancements in sewage-driven microbial fuel cells: novel carbon nanotube cathodes and biomass-derived anodes for efficient renewable energy generation and wastewater treatment

Microbial fuel cells (MFCs) offer a dual solution of generating electrical energy from organic pollutants-laden wastewater while treating it. This study focuses on enhancing MFC performance through innovative electrode design. Three-dimensional (3D) anodes, created from corncobs and mango seeds via controlled graphitization, achieved remarkable power densities. The newly developed electrode configurations were evaluated within sewage wastewater-driven MFCs without the introduction of external microorganisms or prior treatment of the wastewater. At 1,000°C and 1,100°C graphitization temperatures, corncob and mango seed anodes produced 1,963 and 2,171 mW/m2, respectively, nearly 20 times higher than conventional carbon cloth and paper anodes. An advanced cathode composed of an activated carbon-carbon nanotube composite was introduced, rivaling expensive platinum-based cathodes. By optimizing the thermal treatment temperature and carbon nanotube content of the proposed cathode, comparable or superior performance to standard Pt/C commercial cathodes was achieved. Specifically, MFCs assembled with corncob anode with the proposed and standard Pt/C cathodes reached power densities of 1,963.1 and 2,178.6 mW/m2, respectively. Similarly, when utilizing graphitized mango seeds at 1,100°C, power densities of 2,171 and 2,151 mW/m2 were achieved for the new and standard cathodes, respectively. Furthermore, in continuous operation with a flow rate of 2 L/h, impressive chemical oxygen demand (COD) removal rates of 77% and 85% were achieved with corncob and mango seed anodes, respectively. This work highlights the significance of electrode design for enhancing MFC efficiency in electricity generation and wastewater treatment.

Research Progress of Bifunctional Oxygen Reactive Electrocatalysts for Zinc-Air Batteries

Zinc-air batteries (ZABs) have several advantages, including high energy density, cheap price and stable performances with good application prospects in the field of power batteries. The charging and discharging reactions for the air cathode of ZABs are the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively, which play an important role in the whole performance of ZAB. Due to the cost and limited reserves of highly active precious metal catalysts, it is crucial to design alternative efficient and stable dual-functional non-precious metal catalysts. In the present review, we present a systematic summary of the recent progress in the use of transition metal-based electrocatalysts as alternatives to precious metals for the positive poles of ZAB air. Combined with state-of-the-art in situ characterization technologies, a deep understanding of the catalytic mechanism of OER/ORR provided unique insights into the precise design of excellent synthetic non-precious metal catalysts from the perspective of atomic structure. This review further shows that the hybrid electric battery is a new strategy to improve the efficiency of the hybrid electric battery, which could be available to alleviate the problem of resource shortage. Finally, the challenges and research trends for the future development of ZABs were clearly proposed.

Transition Metal Nitrides for Electrocatalytic Application: Progress and Rational Design

The energy crisis and environmental issues are becoming more severe due to the long-term consumption of fossil fuels. Therefore, novel energy-conversion devices with high energy density and environmental friendliness are expected to provide reliable alternatives to traditional fossil-based energy systems. However, because of the inevitable use of costly precious metals as the electrode catalysts for such devices, their popularization is seriously hindered. Transition metal nitrides (TMNs) exhibit similar surface and adsorption properties to noble metals because the atomic distance between metal atoms increases and the d-band center of metal atoms downshifts after nitrogen atoms enter the metal lattice. TMNs have become one of the best electrode materials to replace noble metal-based electrocatalysts in next-generation energy-storage and energy-conversion devices. In this review, the recent developments in the electrocatalytic application of TMNs are covered. First, we discuss the structure and activity origin of TMNs and introduce the common synthesis methods for the preparation of TMNs. Subsequently, we illustrate the applications of mono-metallic TMNs and multi-metallic TMNs in oxygen-reduction reaction, oxygen-evolution reaction, and bifunctional oxygen reduction and evolution reactions. Finally, we summarize the challenges of TMNs encountered at the present stage, and expect their future development.

Novel electrical properties and applications in kaleidoscopic graphene nanoribbons

As one of the representatives of nano-graphene materials, graphene nanoribbons (GNRs) have more novel electrical properties, highly adjustable electronic properties, and optoelectronic properties than graphene due to their diverse geometric structures and atomic precision configurations. The electrical properties and band gaps of GNRs depend on their width, length, boundary configuration and other elemental doping, etc. With the improvement of the preparation technology and level of GNRs with atomic precision, increasing number of GNRs with different configurations are being prepared. They all show novel electrical properties and high tunability, which provides a broad prospect for the application of GNRs in the field of microelectronics. Here, we summarize the latest GNR-based achievements in recent years and summarize the latest electrical properties and potential applications of GNRs.

Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids' surface functionalization in a nonpolar solvent.