Shape-Controlled Synthesis of Surface-Clean Ultrathin Palladium Nanosheets by Simply Mixing a Dinuclear PdICarbonyl Chloride Complex with H2O

Wet-chemistry synthesis of two-dimensional Pt- and Pd-based intermetallic electrocatalysts for fuel cells

Two-dimensional (2D) noble-metal-based nanomaterials have attracted tremendous attention and have widespread promising applications as a result of their unique physical, chemical, and electronic properties. Especially, 2D Pt- and Pd-based intermetallic nanoplates (IMNPs) and nanosheets (IMNSs) are widely studied for fuel cell (FC)-related reactions, including the cathodic oxygen reduction reaction (ORR) and anodic formic acid, methanol and ethanol oxidation reactions (FAOR, MOR and EOR). Wet-chemistry synthesis is a powerful strategy to prepare metallic nanocrystals with well-controlled dispersity, size, and composition. In this review, a fundamental understanding of the FC-related reactions is firstly elaborated. Subsequently, the current wet-chemistry synthesis pathways for 2D Pt- and Pd-based IMNPs and IMNSs are briefly summarized, as well as their electrocatalytic applications including in the ORR, FAOR, MOR, and EOR. Finally, we provide an overview of the opportunities and current challenges and give our perspectives on the development of high-performance 2D Pt- and Pd-based intermetallic electrocatalysts towards FCs. We hope this review offers timely information on the synthesis of 2D Pt- and Pd-based IMNPs and IMNSs and provides guidance for the efficient synthesis and application of them.

Carbon Monoxide Promotes the Catalytic Hydrogenation on Metal Cluster Catalysts

Size effect plays a crucial role in catalytic hydrogenation. The highly dispersed ultrasmall clusters with a limited number of metal atoms are one candidate of the next generation catalysts that bridge the single-atom metal catalysts and metal nanoparticles. However, for the unfavorable electronic property and their interaction with the substrates, they usually exhibit sluggish activity. Taking advantage of the small size, their catalytic property would be mediated by surface binding species. The combination of metal cluster coordination chemistry brings new opportunity. CO poisoning is notorious for Pt group metal catalysts as the strong adsorption of CO would block the active centers. In this work, we will demonstrate that CO could serve as a promoter for the catalytic hydrogenation when ultrasmall Pd clusters are employed. By means of DFT calculations, we show that Pd _n  (n = 2-147) clusters display sluggish activity for hydrogenation due to the too strong binding of hydrogen atom and reaction intermediates thereon, whereas introducing CO would reduce the binding energies of vicinal sites, thus enhancing the hydrogenation reaction. Experimentally, supported Pd₂CO catalysts are fabricated by depositing preestablished [Pd₂(μ-CO)₂Cl₄]^2- clusters on oxides and demonstrated as an outstanding catalyst for the hydrogenation of styrene. The promoting effect of CO is further verified experimentally by removing and reintroducing a proper amount of CO on the Pd cluster catalysts.

Rational Design of Multisite Trielement Ru-Ni-Fe Alloy Nanocatalysts with Efficient and Durable Catalytic Hydrogenation Performances

The co-decomposition of non-noble metals into Ru nanoparticles (NPs) would provide multiple active centers as well as synergistically alter the reaction pathway, enhancing the catalytic hydrogenation performance. Herein, a facile route for synthesizing trielement Ru-Ni-Fe alloy NPs was proposed. The catalytic hydrogenation performance of NPs was measured using p-nitrophenol as a model. The synergistic effect of these three elements (Ru, Ni, and Fe) and synergistic catalysis of multiple crystal faces greatly improved the catalytic hydrogenation performance of Ru₄₄Ni₂₈Fe₂₈ alloy NPs. Ru with more vacant orbitals showed a strong coordination with BH₄^- for the generation of active H species. Ni played a major role in transporting electrons and active H species, increasing the accessibility of catalytically active sites. Fe could cooperate with BH₄^- to produce active H species and promote electrons transfer. Ru₄₄Ni₂₈Fe₂₈ alloy NPs could be reused and applied for the fabrication of films at the oil-water (ethyl acetate-water) interface. The densely packed Ru₄₄Ni₂₈Fe₂₈ NP films were good Raman substrates for monitoring the complete conversion of 4-nitrothiophenol into 4-aminothiophenol. The rational design of Ru₄₄Ni₂₈Fe₂₈ will broaden the application range of Ru-based catalysts and provide new insights into the rational design of other multisite alloy catalysts.

Promoted Glycerol Oxidation Reaction in an Interface-Confined Hierarchically Structured Catalyst

Confined catalysis in a 2D system is of particular interest owing to the facet control of the catalysts and the anisotropic kinetics of reactants, which suppress side reactions and improve selectivity. Here, a 2D-confined system consisting of intercalated Pt nanosheets within few-layered graphene is demonstrated. The strong metal-substrate interaction between the Pt nanosheets and the graphene leads to the quasi-2D growth of Pt with a unique (100)/(111)/(100) faceted structure, thus providing excellent catalytic activity and selectivity toward one-carbon (C1) products for the glycerol oxidation reaction. A hierarchically porous graphene architecture, grown on carbon cloth, is used to fabricate the confined catalyst bed in order to enhance the mass-diffusion limitation in interface-confined reactions. Owing to its unique 3D porous structure, this graphene-confined Pt catalyst exhibits an extraordinary mass activity of 2910 mA mg_Pt ^-1 together with a formate selectivity of 79% at 60 °C. This paves the way toward rational designs of heterogeneous catalysts for energy-related applications.

A route to support Pt sub-nanoparticles on TiO2 and catalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline at room temperature

We report a method to support Pt sub-nanoparticles on TiO₂.

Self-Supported 3D PdCu Alloy Nanosheets as a Bifunctional Catalyst for Electrochemical Reforming of Ethanol

3D PdCu alloy nanosheets exhibit enhanced electrocatalytic activity toward hydrogen evolution reaction and ethanol oxidation reaction in alkaline media. Simultaneous hydrogen and acetate production via a solar-powered cell for ethanol reforming has been fabricated using the nanosheets as bifunctional electrocatalysts. The device is promising for the production of both hydrogen and value-added chemicals using renewable energy.

Trace surface-clean palladium nanosheets as a conductivity enhancer in hole-transporting layers to improve the overall performances of perovskite solar cells

Surface-clean Pd nanosheets were synthesized and embedded in a hole transport material (HTM) matrix to improve the conductivity of the HTM layer. Applying only a trace amount of Pd nanosheets readily led to a remarkably enhanced performance of perovskite solar cells (PSCs). This finding provides an effective strategy to build efficient charge-transport materials for improving the overall performance of PSCs.

Mechanochemical Synthesis of Free-Standing Platinum Nanosheets and Their Electrocatalytic Properties

Robust, 26 nm thick free-standing platinum nanosheets, an extremely rare morphology for metal nanostructures, are obtained by employing fluid induced shearing force of the order of 1.8 N and differential shear-stress of 0.5 kPa across the diameter of a Te template nanorod undergoing galvanic displacement by Pt⁴⁺ . Corrugation leads to their large surface area and much improved electrocatalytic properties when compared with conventional Pt catalysts.

Thin metal nanostructures: synthesis, properties and applications

Two-dimensional nanomaterials, especially graphene and single- or few-layer transition metal dichalcogenide nanosheets, have attracted great research interest in recent years due to their distinctive physical, chemical and electronic properties as well as their great potentials for a broad range of applications. Recently, great efforts have also been devoted to the controlled synthesis of thin nanostructures of metals, one of the most studied traditional materials, for various applications. In this minireview, we review the recent progress in the synthesis and applications of thin metal nanostructures with a focus on metal nanoplates and nanosheets. First of all, various methods for the synthesis of metal nanoplates and nanosheets are summarized. After a brief introduction of their properties, some applications of metal nanoplates and nanosheets, such as catalysis, surface enhanced Raman scattering (SERS), sensing and near-infrared photothermal therapy are described.