Colloidal nanocrystals for electrochemical reduction reactions

Co engineered CoP catalyst for photochemical CO2 reduction with accelerated electron transfer endowed by the space-charge region

Photocatalytic CO₂ reduction has been regarded as an ideal method to simulate photosynthesis for achieving carbon neutralization. However, poor charge transfer efficiency limits its development. Herein, an efficient Co/CoP@C catalyst was prepared with compact contact of Co and CoP layer by using MOF as precursor. At the interface of Co/CoP, the difference in functionality between the two phases may result in uneven distribution of electrons, thus forming a self-driven space-chare region. In this region, spontaneous electron transfer is guaranteed, thus facilitating the effective separation of photogenerated carriers as well as boosting the utilization of solar energy. Furthermore, the electron density of active site Co in CoP is increased and more active sites are exposed, which promotes the adsorption and activation of CO₂ molecules. Together with suitable redox potential, low energy barrier for *COOH formation and easy desorption of CO, the reduction rate of CO₂ catalyzed by Co/CoP@C is 4 times higher than that of CoP@C.

Ordered SnO2@C Flake Array as Catalyst Support for Improved Electrocatalytic Activity and Cathode Durability in PEMFCs

Pt-SnO2@C-ordered flake array was developed on carbon paper (CP) as an integrated cathode for proton exchange membrane fuel cell through a facile hydrothermal method. In the integrated cathode, Pt nanoparticles were deposited uniformly with a small particle size on the SnO2@C/CP support. Electrochemical impedance spectroscopy analysis revealed lower impedance in a potential range of 0.3-0.5 V for the ordered electrode structure. An electrochemically active surface area and oxygen reduction peak potential determined by cyclic voltammetry measurement verified the synergistic effect between Pt and SnO2, which enhanced the electrochemical catalytic activity. Besides, compared with the commercial carbon-supported Pt catalyst, the as-developed SnO2@C/CP-supported Pt catalyst demonstrated better stability, most likely due to the positive interaction between SnO2 and the carbon coating layer.

Mediated electrochemical synthesis of metal nanoparticles

The review integrates and analyzes data of original studies on the mediated electrosynthesis of metal nanoparticles — a new efficient and environmentally attractive process for obtaining these particles in the solution bulk. The general principles and specific features of electrosynthesis of metal nanoparticles by mediated electroreduction of metal ions and complexes are considered. The discussed issues include the role of cyclic voltammetry in the development of this method, the method efficiency, some aspects of selection of mediators, and aggregation, stabilization and catalytic activity of the metal nanoparticles thus obtained. Analysis of the results of mediated electrosynthesis of Pd, Ag, PdAg, Au, Pt and Cu nanoparticles stabilized by various compounds and mediated electrogeneration of highly active metal particles is used as basic data for discussion.

The bibliography includes 247 references.

Fabrication of palladium-copper nanoparticles with controllable size and chemical composition

A series of Pd_xCu_100-x (x = 20, 40, 60, 80) particles with the sizes of 7-9 nm were fabricated by a two-step polyol reduction process, which differentiated the nucleation and growth steps of the nanoparticles. The primary reduction of Pd²⁺ by ethylene glycol at 393 K formed appreciable amounts of Pd⁰ nuclei, while the subsequent reduction at 473 K fully reduced the Pd²⁺ and Cu²⁺ species with the aid of the initially formed Pd nuclei seeds. Meanwhile, the releasing oleylamine, previously coordinated with metal cations, acted as the capping agent to segregate the nanoparticles. Both parameters simultaneously controlled the assembly kinetics of the bimetallic nanoparticles and resulted in uniform sizes and designed chemical compositions. Among them, the Pd₈₀Cu₂₀ nanoparticles showed quite promising activity and selectivity for the hydrogenation of nitrobenzene under mild conditions.

Three-dimensional carbon architectures for electrochemical capacitors

Three-dimensional (3D) carbon-based materials are emerging as promising electrode candidates for energy storage devices. In comparison to the 1D and 2D structures, 3D morphology offers new opportunities in rational design and synthesis of novel architectures tailor-made for promoting electrochemical performance. The capability of building hierarchical porous structures with 3D configuration can significantly advance the performance of energy storage devices by simultaneously enhancing the ion-accessible surface area and ion diffusion. This feature article presents an overview of recent progress in design, synthesis and implementation of 3D carbon-based materials as electrodes for electrochemical capacitors. Synthesis methodologies of four types of 3D carbon-based electrodes: 3D exfoliated carbon structures, 3D graphene scaffolds, 3D hierarchical porous carbon foams, as well as 3D architectures with periodic pores derived from direct ink writing, are thoroughly discussed and highlighted with selected experimental works. Finally, key opportunities and challenges in which different 3D carbons can significantly impact the energy storage and conversion communities will be provided.

Stabilizer-free silver nanoparticles as efficient catalysts for electrochemical reduction of oxygen

In this work we demonstrated the potential of the He+5% H₂+1% N₂ plasma jet treatment for the synthesis of surfactant-free silver nanoparticles (Ag NPs) with narrow size distribution. The obtained colloidal solutions of electrostatically stabilized Ag NPs do not show any agglomeration for several months. Apart from an atomic thin oxide layer and the relatively weakly bound OH^- ions, the surface of Ag NPs can be considered as stabilizer-free. The surface charge (characterized by the zeta potential) of Ag NPs in solution was measured by electrophoretic light scattering technique. Plasmonic band position and width in the UV/VIS extinction spectra was utilized for the assessment of Ag NPs size distribution. Highly concentrated Ag NPs were uniformly deposited on the surface of the glassy carbon (GC) electrodes by vacuum-drying technique. The deposition process was monitored with a digital camera attached to a microscope. The assemblies of Ag NPs on the electrode surface were characterized by scanning electron microscopy. The Ag NP/GC catalysts were electrochemically tested in alkaline solution using the rotating disk electrode method. The Ag NP/GC electrodes exhibited high electrocatalytic activity toward the oxygen reduction reaction (ORR) in 0.1M KOH solution, indicating their potential applicability as cathode materials for alkaline fuel cells.