Nitrogen-Doped Graphene Aerogel Microspheres Used as Electrocatalyst Supports for Methanol Oxidation

Nitrogen and Sulfur Co-Doped Graphene Composite Aerogel Microspheres Supporting Pt Electrode-Catalyzed Methanol Electro-Oxidation Reaction

Nitrogen and sulfur co-doped graphene composite aerogel microspheres containing pyrolyzed carbon (NS-GAMs@C) are prepared by pressure-spraying the graphene oxide (GO) dispersion with water-soluble phenolic resin and thiourea, followed by freeze shaping, freeze-drying, and high-temperature carbonization. The resulting NS-GAMs@C possesses interconnected porous structures with large surface areas and high doping levels of N/S elements. Furthermore, the platinum nanoparticles (Pt NPs) are grown onto the NS-GAMs@C via a solvothermal reduction reaction to obtain the Pt/NS-GAMs@C microspheres with an average particle size of ∼32.25 μm. The residual carbon species in situ formed by the high-temperature carbonization of phenolic resin can act as intercalation compounds to reduce the self-stacking of graphene sheets, which contributes to an enhanced specific surface area and doping level. The N/S co-doping in NS-GAMs@C improves the interaction between the Pt and carriers, reduces the size of Pt NPs, ensures their even distribution, and increases the proportion of highly active Pt (111) crystal planes. Consequently, the methanol oxidation activity of Pt/NS-GAMs@C is significantly improved compared to undoped materials. Specifically, the optimized Pt/NS-GAMs@C composites demonstrate a remarkable mass activity of 840.11 mA·mg-1 Pt for methanol electrooxidation, which is approximately 2.39, 3.94, 3.41, and 1.75 times higher than that of commercial Pt/C, Pt/rGO (reduced GO), Pt/GAMs without doping, and Pt/NS-GAB@C (bulk aerogel), respectively. Additionally, the Pt/NS-GAMs@C exhibits long-term electrocatalytic stability. This research provides a novel catalyst system based on aerogel microspheres for methanol electrooxidation fuel cells.

Advancements in Noble Metal-Decorated Porous Carbon Nanoarchitectures: Key Catalysts for Direct Liquid Fuel Cells

Noble-metal nanocrystals have emerged as essential electrode materials for catalytic oxidation of organic small molecule fuels in direct liquid fuel cells (DLFCs). However, for large-scale commercialization of DLFCs, adopting cost-effective techniques and optimizing their structures using advanced matrices are crucial. Notably, noble metal-decorated porous carbon nanoarchitectures exhibit exceptional electrocatalytic performances owing to their three-dimensional cross-linked porous networks, large accessible surface areas, homogeneous dispersion (of noble metals), reliable structural stability, and outstanding electrical conductivity. Consequently, they can be utilized to develop next-generation anode catalysts for DLFCs. Considering the recent expeditious advancements in this field, this comprehensive review provides an overview of the current progress in noble metal-decorated porous carbon nanoarchitectures. This paper meticulously outlines the associated synthetic strategies, precise microstructure regulation techniques, and their application in electrooxidation of small organic molecules. Furthermore, the review highlights the research challenges and future opportunities in this prospective research field, offering valuable insights for both researchers and industry experts.

Ultrahigh Mass Activity Pt Entities Consisting of Pt Single atoms, Clusters, and Nanoparticles for Improved Hydrogen Evolution Reaction

Platinum is one of the best-performing catalysts for the hydrogen evolution reaction (HER). However, high cost and scarcity severely hinder the large-scale application of Pt electrocatalysts. Constructing highly dispersed ultrasmall Platinum entities is thereby a very effective strategy to increase Pt utilization and mass activities, and reduce costs. Herein, highly dispersed Pt entities composed of a mixture of Pt single atoms, clusters, and nanoparticles are synthesized on mesoporous N-doped carbon nanospheres. The presence of Pt single atoms, clusters, and nanoparticles is demonstrated by combining among others aberration-corrected annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and electrochemical CO stripping. The best catalyst exhibits excellent geometric and Pt HER mass activity, respectively ≈4 and 26 times higher than that of a commercial Pt/C reference and a Pt catalyst supported on nonporous N-doped carbon nanofibers with similar Pt loadings. Noteworthily, after optimization of the geometrical Pt electrode loading, the best catalyst exhibits ultrahigh Pt and catalyst mass activities (56 ± 3 A mg^-1 _Pt and 11.7 ± 0.6 A mg^-1 _Cat at -50 mV vs. reversible hydrogen electrode), which are respectively ≈1.5 and 58 times higher than the highest Pt and catalyst mass activities for Pt single-atom and cluster-based catalysts reported so far.