Ultrathin PdPtP nanodendrites as high-activity electrocatalysts toward alcohol oxidation

PdPtP nanodendrites were prepared by a post-phosphating method. Due to their well-designed structure and composition, the EOR activity of the PtPdP NDs is significantly increased to 14.3 A mgPd+Pt-1, which is a significant improvement compared to commercial Pd/C catalysts. In addition, stability tests demonstrated their excellent catalytic activity and structural durability.

Adjusting grain boundary within NiCo2O4rod arrays by phosphating reaction for efficient hydrogen production

In this work, the density and electronic structures of the metal active sites in NiCo₂O₄nanorod arrays were concurrently tuned by controlling the sample's exposure time in a phosphorization process. The results showed that both the density and electronic structure of the active adsorption sites played a key role towards the catalytic activity for water splitting to produce hydrogen. The optimal catalyst exhibited 81 mV overpotential for hydrogen evolution reaction (HER) at 10 mA cm^-2and 313 mV overpotential towards oxygen evolution reaction at 50 mA cm^-2. The assembled electrode delivered a current density of 50 mA cm^-2at 1.694 V in a fully functional water electrolyzer. The further results of theoretical density functional theory calculations revealed the doping of P elements lowered down the H adsorption energies involved in the water splitting process on the various active sites of P-NiCo₂O₄-10 catalyst, and thus enhanced its HER catalytic activities.

Surfactant-free self-assembly to the synthesis of MoO3 nanoparticles on mesoporous SiO2 to form MoO3/SiO2 nanosphere networks with excellent oxidative desulfurization catalytic performance

Recently, oxidative desulfurization (ODS) is favoured by researchers because it is based on mild conditions and does not consume hydrogen. However, the preparation process of catalyst for ODS was not green or costly, which limits its further industrial applications. In this study, a facile route has been explored to grow the mesoporous MoO₃/SiO₂ nanosphere networks (MoO₃/SiO₂ NN) using low-cost air without surfactants. Herein, the air not only served as the template to self-assemble and form the nanosphere network structure but acted as a mesopore-directing agent to make mesopores on the MoO₃/SiO₂ nanosphere. Moreover, the recovered waste mother liquor was also successfully applied to prepare nanomaterials. Gratifyingly, the nanocomposites of MoO₃/SiO₂ NN displayed remarkable pore structure, large specific surface area (201 m²  g^-1) and excellent amphipathy (CA = 24.7° and 13.6° of water and n-octane, respectively) making it a promising catalyst for two-phase ODS reaction with H₂O₂ as an oxidant. Meanwhile, the high TOF value (56.6 h^-1) and outstanding durability were obtained under optimum conditions (Yield > 99 % at 70 °C and O/S = 8:1 for 1 h, 20 mg catalyst) and the products were detected by GC-MS and ¹H NMR. Therefore, an environmentally benign self-assembly procedure can facilely prepare more types of mesoporous catalysts for large-scale industrial application.

3D porous nanostructured Ni3N-Co3N as a robust electrode material for glucose fuel cell

Metal nitrides are broadly applicable in the field of electrochemistry due to their excellent electrical properties. In this study, a 3D nanostructured Ni₃N-Co₃N catalyst was prepared by using a versatile urea glass method, and was tested as an anode catalyst for a glucose fuel cell. The synthesized Ni₃N-Co₃N exhibits uniform particle dispersion in structure, morphology, and composition, and has a interpenetrating three-dimensional network structure. Notably, the Ni₃N-Co₃N significantly improved the catalytic activity of glucose oxidation compared to Ni₃N, Co₃N, and conventional activated carbon electrodes. The superior electrochemical performance could be attributed to its porous structure and unique properties, which provided a fast transport network for charge and mass transfer as well as good synergetic effect. The glucose fuel cell equipped with a Ni₃N-Co₃N anode achieved 30.89 W m^-2 power and 97.66 A m^-2 current densities at room temperature. This investigation provides potential directions for the design of cost-effective bimetallic catalysts for a wide range of glucose fuel cell applications.

Three-dimensional PdCuM (M = Ru, Rh, Ir) Trimetallic Alloy Nanosheets for Enhancing Methanol Oxidation Electrocatalysis

Owing to their intrinsically high activity and rich active sites on the surface, noble metal materials with an ultrathin two-dimensional nanosheet structure are emerging as ideal catalysts for boosting fuel cell reactions. However, the realization of controllable synthesis of multimetallic Pd-based alloy ultrathin nanosheets (NSs) for achieving enhanced electrocatalysis evolved from compositional and structural advantages remains a grand challenge. Herein, we report a universal method for the construction of a new series of the three-dimensional (3D) multimetallic PdCuM (M = Ru, Rh, Ir) superstructures that consist of ultrathin alloy NSs. Different from the conventional 2D ultrathin nanostructure, the 3D PdCuM NSs that endowed with abundant routes for fast mass transport, high noble material utilization efficiency, and ligand effect from M to PdCu display large promotion in electrocatalytic performance for the methanol oxidation reaction. Impressively, the composition-optimized Pd₅₉Cu₃₃Ru₈ NSs, Pd₅₇Cu₃₄Rh₉ NSs, and Pd₆₃Cu₂₉Ir₈ NSs show the mass activities of 1660.8, 1184.4, and 1554.8 mA mg^-1 in alkaline media, which are 4.9, 3.5, and 4.6-fold larger than that of commercial Pd/C, respectively. More importantly, all of the PdCuM NSs are also very stable for long-term electrochemical tests.

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

The use of ethanol as a fuel in direct alcohol fuel cells depends not only on its ease of production from renewable sources, but also on overcoming the challenges of storage and transportation. In an ethanol-based fuel cell, highly active electrocatalysts are required to break the C-C bond in ethanol for its complete oxidation at lower overpotentials, with the aim of increasing the cell performance, ethanol conversion rates, and fuel efficiency. In recent decades, the development of wet-chemistry methods has stimulated research into catalyst design, reactivity tailoring, and mechanistic investigations, and thus, created great opportunities to achieve efficient oxidation of ethanol. In this Minireview, the nanomaterials tested as electrocatalysts for the ethanol oxidation reaction in acid or alkaline environments are summarized. The focus is mainly on nanomaterials synthesized by using wet-chemistry methods, with particular attention on the relationship between the chemical and physical characteristics of the catalysts, for example, catalyst composition, morphology, structure, degree of alloying, presence of oxides or supports, and their activity for ethanol electro-oxidation. As potential alternatives to noble metals, non-noble-metal catalysts for ethanol oxidation are also briefly reviewed. Insights into further enhancing the catalytic performance through the design of efficient electrocatalysts are also provided.

Monodisperse ordered indium-palladium nanoparticles: synthesis and role of indium for boosting superior electrocatalytic activity for ethanol oxidation reaction

The slow kinetics of ethanol oxidation reaction (EOR) has limited its widespread use for fuel cells. Bimetallic catalysts with optimized surface compositions can considerably govern rate-determining steps through selectivity for CH3COOH formation or by facilitating the adsorption of OHadsvia the bifunctional effect of an alloy to increase the EOR's kinetic rates. Here, we reported monodisperse ordered In-Pd nanoparticles as new bimetallic high-performance catalysts for EOR. In-Pd nanoparticles, i.e., In3Pd2 and In3Pd5 were prepared using arrested precipitation in solution, and their composition, structures, phase and crystallinity were confirmed using a variety of analyses including TEM, XPS, EDS and XRD. In-Pd nanoparticles were loaded on carbon black (Vulcan XC-72) as electrocatalysts for EOR in alkaline media. In3Pd2 and In3Pd5 nanoparticles exhibited 5.8 times and 4.0 times higher mass activities than commercial Pd/C, which showed that the presence of indium greatly boosts electrocatalytic reactivity for EOR of Pd catalysts. This performance is the best among those of bimetallic nanoparticles reported to date. Such high performance of In-Pd nanoparticles may be attributed to the following two reasons. First, In-Pd nanoparticles exhibited excellent CO anti-poison ability, as confirmed by CO striping experiments. Second, as revealed by DFT calculations of metals with OHads adsorption, In atoms on In3Pd2 surface exhibited the lowest energy (-1.659 eV) for OHads adsorption as compared to other common oxophilic metals including Sn, SnPt, Ag, Ge, Co, Pb, and Cu. We propose that the presence of indium sites promoted efficient free OH radical adsorption on indium sites and resulted in a faster reaction rate of acetate formation from acetaldehyde (the rate determining step for EOR on Pd sites). Finally, a single direct ethanol fuel cell (DEFC) with Pd/C anode was prepared. Compared to the results for a commercial Pd/C anode, the open circuit voltage (OCV) of In3Pd2/C improved by 0.25 V (from 0.64 to 0.89 V) and the power density improved by ∼80% (from 3.7 to 6.7 mW cm-2), demonstrating its practical uses as Pt or Pd catalyst alternatives for DEFC.

Improved ethanol electrooxidation performance by shortening Pd-Ni active site distance in Pd-Ni-P nanocatalysts

Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. However, effects of the distance between the noble metal and oxophilic metal active sites on the catalytic performance have rarely been investigated. Herein, we report on ultrasmall (∼5 nm) Pd–Ni–P ternary nanoparticles for ethanol electrooxidation. The activity is improved up to 4.95 A per mg_Pd, which is 6.88 times higher than commercial Pd/C (0.72 A per mg_Pd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni–P heterodimers into Pd–Ni–P nanoparticles and tuning the Ni/Pd atomic ratio to 1:1. Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals (on Ni active sites) which facilitate the oxidative removal of carbonaceous poison and combination with CH₃CO radicals on adjacent Pd active sites.

Incorporating oxophilic metals into noble metal catalysts can improve electrocatalytic performance; however, the influence of the distance between noble metal and oxophilic metal active site is not well understood. Here the authors make Pd–Ni–P nanocatalysts for ethanol oxidation, with improved performance achieved by shortening the Pd–Ni distance.

The green synthesis of ultrafine palladium–phosphorus alloyed nanoparticles anchored on polydopamine functionalized graphene used as an excellent electrocatalyst for ethanol oxidation

A new catalyst, consisting of ultrafine Pd–P alloyed nanoparticles (NPs) anchored on polydopamine functionalized graphene (Pd–P/PDA-GS), was fabricated by a green, facile and surfactant free method for ethanol electrocatalytic oxidation reaction (EOR).

Aqueous sodium borohydride induced thermally stable porous zirconium oxide for quick removal of lead ions

Aqueous sodium borohydride (NaBH4) is well known for its reducing property and well-established for the development of metal nanoparticles through reduction method. In contrary, this research paper discloses the importance of aqueous NaBH4 as a precipitating agent towards development of porous zirconium oxide. The boron species present in aqueous NaBH4 play an active role during gelation as well as phase separated out in the form of boron complex during precipitation, which helps to form boron free zirconium hydroxide [Zr(OH)4] in the as-synthesized condition. Evolved in-situ hydrogen (H2) gas-bubbles also play an important role to develop as-synthesized loose zirconium hydroxide and the presence of intra-particle voids in the loose zirconium hydroxide help to develop porous zirconium oxide during calcination process. Without any surface modification, this porous zirconium oxide quickly adsorbs almost hundred percentages of toxic lead ions from water solution within 15 minutes at normal pH condition. Adsorption kinetic models suggest that the adsorption process was surface reaction controlled chemisorption. Quick adsorption was governed by surface diffusion process and the adsorption kinetic was limited by pore diffusion. Five cycles of adsorption-desorption result suggests that the porous zirconium oxide can be reused efficiently for removal of Pb (II) ions from aqueous solution.

Scalable synthesis of Cu-based ultrathin nanowire networks and their electrocatalytic properties

In this research, we developed an easy way to generate CuM (M = Pd, Pt and PdPt) ultrathin nanowire networks by simply injecting the metallic precursors into an aqueous solution which contained sodium borohydride under vigorous stirring. The reaction can be finished quickly without needing any other reagents, thus leaving the products with a clean surface. The prepared materials show an ultrathin diameter of less than 5 nanometers. The reaction can be easily amplified, resulting in scalable products. These properties combined with the superior catalytic performance of the prepared CuM nanowire networks underpin their potential use in glycerol electrooxidation reaction.

Preparation of Au@Ag nanoparticles at a gas/liquid interface and their application for sensitive detection of hydrogen peroxide

Preparation of Au@Ag NPs at a gas/liquid interface by a seed-mediated growth procedure and their application for sensitive detection of hydrogen peroxide.

Liquid–liquid interface-mediated room-temperature synthesis of amorphous NiCo pompoms from ultrathin nanosheets with high catalytic activity for hydrazine oxidation

Ni_xCo_y alloy pompoms formed by the aggregation of nano ultrathin sheets were prepared by simultaneous reduction of NiCl₂ and CoCl₂ with NaBH₄via a liquid–liquid interface reaction.

Synthesis of dendritic Pt–Ni–P alloy nanoparticles with enhanced electrocatalytic properties

Dendritic Pt–Ni–P nanoparticles were synthesizedviaa wet-chemical route, exhibiting a higher electrocatalytic activity than dendritic Pt–Ni nanoparticles and commercial Pt/C.

Room-temperature synthesis with inert bubble templates to produce “clean” PdCoP alloy nanoparticle networks for enhanced hydrazine electro-oxidation

PdCoP alloy nanoparticle networks prepared using inert bubbles as template exhibited high activity for hydrazine oxidation.

Amorphous PtNiP particle networks of different particle sizes for the electro-oxidation of hydrazine

Amorphous PtNiP particle networks with different particle sizes prepared via the reaction temperature control method showed high catalytic activity for hydrazine oxidation compared to the Pt and PtNi catalysts due to its porous, amorphous structure.