Preparation of highly dispersed palladium–phosphorus nanoparticles and its electrocatalytic performance for formic acid electrooxidation

Highly Enantioselective Binaphthyl-Based Chiral Phosphoramidite Stabilized-Palladium Nanoparticles for Asymmetric Suzuki C-C Coupling Reactions

The optically pure binaphthyl-based phosphoramidite ligands and their perfluorinated analogs have been first used for the preparation of chiral palladium nanoparticles (PdNPs). These PdNPs have been extensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ³¹P NMR, and thermogravimetric analysis techniques. The circular dichroism(CD) analysis of chiral PdNPs exhibited negative cotton effects. Perfluorinated phosphoramidite ligands provided smaller (2.32-3.45 nm) and well-defined nanoparticles, in comparison with the nonfluorinated analog (4.12 nm). The catalytic behavior of binaphthyl-based phosphoramidite stabilized chiral PdNPs has been investigated in the asymmetric Suzuki C-C coupling reactions for the formation of sterically hindered binaphthalene units, and high isolated yields (up to 85%) were achieved with excellent enantiomeric excesses (>99% ee). Recycling studies revealed that chiral PdNPs could be reused over 12 times without significant loss in activity and enantioselectivity (>99% ee). The nature of the active species was also investigated with a combination of poisoning and hot filtration tests and found that catalytically active species is the heterogeneous nanoparticles. These results indicate that the use of phosphoramidite ligands as a stabilizer for developing efficient and unique chiral nanoparticles could open up a field for many other asymmetric organic transformations promoted by chiral catalysts.

Emerging interstitial/substitutional modification of Pd-based nanomaterials with nonmetallic elements for electrocatalytic applications

Palladium (Pd)-based nanomaterials have been identified as potential candidates for various types of electrocatalytic reaction, but most of them typically exhibit unsatisfactory performances. Recently, extensive theoretical and experimental studies have demonstrated that the interstitial/substitutional modification of Pd-based nanomaterials with nonmetallic atoms (H, B, C, N, P, S) has a significant impact on their electronic structure and thus leads to the rapid development of one kind of promising catalyst for various electrochemical reactions. Considering the remarkable progress in this area, we highlight the most recent progress regarding the innovative synthesis and advanced characterization methods of nonmetallic atom-doped Pd-based nanomaterials and provide insights into their electrochemical applications. What's more, the unique structure- and component-dependent electrochemical performance and the underlying mechanisms are also discussed. Furthermore, a brief conclusion about the recent progress achieved in this field as well as future perspectives and challenges are provided.

Recent advances in phosphorus containing noble metal electrocatalysts for direct liquid fuel cells

Direct liquid fuel cells (DLFCs) are considered as satisfactory alternatives to traditional fossil fuels owing to their unique advantages, e.g. environmental friendliness and easy storage. Noble metal catalysts are widely used to improve the efficiency of DLFCs. However, the high cost, low utilization and poor stability of noble metals restricted their practical applications. Therefore, it is of great significance to explore cost-effective electrocatalysts and further improve their electrocatalytic performance. Reducing the content of noble metals by adding low-priced phosphorus (P) has been considered as an effective strategy, which is able to enhance their electrocatalytic activity and anti-poisoning ability through effectively changing the electronic density of active sites. In the past few years, tremendous P containing catalysts have been synthesized and utilized in DLFCs. In this review, we summarize the fundamentals of electrochemical reactions and present recent progress in P containing noble metal catalysts for DLFCs, including the discussion of their shape, composition and the relationship between P and active sites. Finally, the challenges and some potential directions in this field are pointed out.

A review on advances in green treatment of glycerol waste with a focus on electro-oxidation pathway

Over the past decades, research efforts are being devoted into utilizing the biomass waste as a major source of green energy to maintain the economic, environmental, and social sustainability. Specifically, there is an emerging consensus on the significance of glycerol (an underutilised waste from biodiesel industry) as a cheap, non-toxic, and renewable source for valuable chemicals synthesis. There are numerous methods enacted to convert this glycerol waste to tartronic acid, mesoxalic acid, glyceraldehyde, dihydroxyacetone, oxalic acid and so on. Among these, the green electro-oxidation technique is one of the techniques that possesses potential for industrial application due to advantages such as non-toxicity process, fast response, and lower energy consumption. The current review covers the general understanding on commonly used techniques for alcohol (C₁ & C₂) conversion, with a specific insight on glycerol (C₃) electro-oxidation (GOR). Since catalysts are the backbone of chemical reaction, they are responsible for the overall economy prospect of any processes. To this end, a comprehensive review on catalysts, which include noble metals, non-noble metals, and non-metals anchored over various supports are incorporated in this review. Moreover, a fundamental insight into the development of future electrocatalysts for glycerol oxidation along with products analysis is also presented.

Optimized Synthesis of Nitrogen and Phosphorus Dual-Doped Coal-Based Carbon Fiber Supported Pd Catalyst with Enhanced Activities for Formic Acid Electrooxidation

Development of a Pd-based catalyst with highly active and durable properties for formic acid oxidation reaction at the anode remains an important matter of interest in the research community. Herein, we have designed novel coal-based carbon fibers (Coal-CFs) with dicyandiamide (DCD) as nitrogen (N) source, triphenylphosphine (TPP) as phosphorus (P) source dual-doped to support Pd catalysts (Pd/NP-Coal-CFs(DCD/TPP)), which exhibit superior catalytic performance toward formic acid oxidation reaction. Mass activity of formic acid oxidation of Pd/NP-Coal-CFs(DCD/TPP) catalyst is 536.6 mA·mg^-1_Pd, which is 2.5 times higher than that of Pd/Coal-CFs catalyst. The higher specific surface areas, exclusive electron transport path, and the high synergistic interaction of N and P are the favorable phenomena for catalytic performance. The addition of coal not only increases the abundant defects sites but also makes the utilization of coal with high added value. This N and P dual-doped catalyst inspires an idea for promoting applications in practical fuel cells.

Fabrication of Pd/P nanoparticle networks with high activity for methanol oxidation

The as-prepared Pd/P nanoparticle networks efficiently exhibit electrocatalytic activity and stability for methanol oxidation.

Facile synthesis of 3D Pd–P nanoparticle networks with enhanced electrocatalytic performance towards formic acid electrooxidation

3D Pd–P nanoparticle networks (NNs) have been successfully synthesized using a facile one-step soft-template-assisted method. The as-prepared Pd–P NNs exhibit markedly improved activity and stability towards formic acid electrooxidation over Pd NNs, commercial Pd/C and Pd–P nanoparticle aggregates (NAs).

Polyallylamine-directed green synthesis of platinum nanocubes. Shape and electronic effect codependent enhanced electrocatalytic activity

The synthesis of Pt nanocrystals with controlled size and morphology has drawn enormous interest due to their particular catalytic activity. We present a facile and green hydrothermal method for synthesizing monodisperse Pt nanocubes (Pt-NCs) with polyallylamine hydrochloride (PAH) as a complex-forming agent, capping agent and facet-selective agent, and formaldehyde as a reductant. The formation mechanism, particle size and surface composition of the Pt-NCs were investigated by Ultraviolet and visible spectroscopy (UV-vis), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), etc. In the proposed PAH-K(2)PtCl(4)-HCHO synthesis system, the raw material could be reutilized to re-synthesize the Pt-NCs, and the particle size of the Pt-NCs could be readily controlled by the reduction rate of the Pt(II) species in the Pt(II)-PAH complex. After UV/Ozone and electrochemical cleaning, the residual PAH on the Pt-NC surfaces still strongly influenced the d-band centre of Pt due to the strong N-Pt interaction. The as-prepared 6 nm Pt-NCs showed superior electrocatalytic activity (mass activity and specific activity) and stability towards the oxygen reduction reaction (ORR) in both H(2)SO(4) and HClO(4) electrolytes compared to the commercial E-TEK Pt black, owing to the combination of the facets effect and electronic effect.

Polyallylamine functionalized palladium icosahedra: one-pot water-based synthesis and their superior electrocatalytic activity and ethanol tolerant ability in alkaline media

Polyallylamine (PAH) functionalized Pd icosahedra are synthesized through a simple, one-pot, seedless and hydrothermal growth method. Herein, PAH is used efficiently as a complex-forming agent, capping agent, and facet-selective agent. The strong interaction between PAH and Pd atom sharply changes the electronic structure of Pd atom in the Pd icosahedra. The protective function of PAH layers and enhanced antietching capability of Pd atom are responsible for the formation of the Pd icosahedra. Very importantly, the as-prepared PAH functionalized Pd icosahedra exhibit superior electrocatalytic activity and ethanol tolerant ability toward the oxygen reduction reaction (ORR) compared to the commercially available Pt black in alkaline media. At 0.95 V (vs RHE), the ORR specific kinetic current density at the Pd icosahedra is 4.48 times higher than that at commercial Pt black. The fact demonstrates the appropriate surface modification of the Pd nanoparticles by nonmetallic molecules can be regarded as an effective way to enhance the electrocatalytic activity toward the ORR.