Small‐Sized Tungsten Nitride Particles Strongly Anchored on Carbon Nanotubes and their Use as Supports for Pt for Methanol Electro‐oxidation

The anchoring of small‐sized WN (tungsten nitride) nanoparticles (NPs) with good dispersion on carbon nanotubes (CNTs) offers an effective means of obtaining promising materials for use in electrocatalysis. Herein, an effective method based on grinding treatment followed by a nitridation process is proposed to realize this goal. In the synthesis, a solution containing H₄[SiO₄(W₃O₉)₄] (SiW₁₂) and CNTs modified with polyethylenimine (PEI‐CNTs) was ground to dryness. Small‐sized WN NPs were anchored onto the CNTs with good dispersion after calcination under NH₃. Under hydrothermal assembly conditions (absence of grinding), WN particles of larger size and with inferior dispersion were obtained, demonstrating the important role of the grinding process. The benefit of the small‐sized WN has been demonstrated by using WN/CNTs as a support for Pt to catalyze the methanol electro‐oxidation reaction. The mass activity of Pt‐WN/CNTs‐G‐70 (where G denotes the grinding treatment, and 70 is the loading amount (%) of WN in the WN/CNTs) was evaluated as about 817 mA mg^?1_Pt, better that those of commercial Pt/C (340 mA mg^?1_Pt) and Pt/CNTs (162 mA mg^?1_Pt). The Pt‐WN/CNTs‐G also displayed good CO tolerance. In contrast, Pt‐WN/CNTs prepared without the grinding process displayed an activity of 344 mA mg^?1_Pt, verifying the key role of grinding treatment in the preparation of WN/CNTs with good co‐catalytic effect.     

Pd/CNT Catalysts for Glycerol Electro‐oxidation: Effect of Pd Loading on Production of Valuable Chemical Products

Glycerol (C₃H₈O₃), a waste product of biodiesel, is considered as a suitable substrate for electro‐oxidation process to generate high value‐added products. A suitable active catalyst could improve the yield of desirable organic compounds from electro‐oxidation of glycerol. In this work, palladium nanoparticles supported over activated multi‐walled carbon nanotubes (MWCNTs) with varying loadings of 5 %–40 % were prepared using chemical reduction method and used to study their potential for electro‐oxidation of glycerol to produce various high value‐added products. The catalysts were characterized by different physicochemical methods, such as X‐ray diffraction (XRD), N₂ adsorption‐desorption, and Transmission electron microscopy (TEM), whereas the electro‐oxidation activity of the catalysts was analysed using cyclic voltammetry (CV) and chronoamperometry (CA), and the products were identified by high performance liquid chromatography (HPLC). The electrochemical surface area (S_ESA) and mass activity (MA) were increased from 176.98 m² g^?1 to 282.29 m² g^?1 and 12.22 mA mg^?1 to 49.53 mA mg^?1 by increasing the Pd‐loading from 5 % to 20 %, respectively. While the further increase to 40 % Pd loading, the S_ESA and MA values decreased to 231.45 m² g^?1 and 47.63 mA mg^?1respectively. The results found that the optimum 20 % Pd‐loading showed the excellent electrochemical properties due to uniform distribution of Pd‐metal particles over MWCNTs. High performance liquid chromatography (HPLC) showed the tartronic acid, glyceric acid and glyceraldehyde as dominant products. Mechanism of the reaction has also been proposed based on product distribution.     

Nanocomposite of Platinum Particles Embedded into Nanosheets of Polycarbazole for Methanol Oxidation

Nanoparticles of Pt were successfully electrodeposited onto polycarbazole (PCz) film on a stainless steel (SS‐PCz‐Pt) by chronocoulometry (0.2 C). For comparative purposes, Pt particles were deposited into stainless steel (SS‐Pt) under the same condition. Fourier transform infrared spectroscopy (FT‐IR) results confirmed PCz exists in the SS‐PCz‐Pt composite electrode. X‐ray photoelectron spectroscopy (XPS) results indicated that PCz of SS‐PCz can interact easily with Pt particles. The crystalline behavior and morphology of SS‐PCz‐Pt and SS‐Pt were determined by X‐ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and Transmission Electron Microscopy (TEM). The TEM results indicated that Pt particles disperse more uniformly into the nanosheets of polycarbazole than those of SS film. Catalytic activity and stability for the oxidation of methanol were studied by using cyclic voltammetry and chronoamperometry. A high catalytic current for methanol oxidation (8.04 mA cm^?2 mg^?1) was found for the SS‐PCz‐Pt electrode in comparison to SS‐Pt electrode (5.01 mA cm^?2 mg^?1) at about 0.6 V (vs. Ag/AgCl).     

Methanol Oxidation at Platinum Coated Black Titania Nanotubes and Titanium Felt Electrodes

Optimized Pt-based methanol oxidation reaction (MOR) anodes are essential for commercial direct methanol fuel cells (DMFCs) and methanol electrolyzers for hydrogen production. High surface area Ti supports are known to increase Pt catalytic activity and utilization. Pt has been deposited on black titania nanotubes (bTNTs), Ti felts and, for comparison, Ti foils by a galvanic deposition process, whereby Pt(IV) from a chloroplatinate solution is spontaneously reduced to metallic Pt (at 65 °C) onto chemically reduced (by CaH₂) TNTs (resulting in bTNTs), chemically etched (HCl + NaF) Ti felts and grinded Ti foils. All Pt/Ti-based electrodes prepared by this method showed enhanced intrinsic catalytic activity towards MOR when compared to Pt and other Pt/Ti-based catalysts. The very high/high mass specific activity of Pt/bTNTs (ca 700 mA mg_Pt⁻¹ at the voltammetric peak of 5 mV s⁻¹ in 0.5 M MeOH) and of Pt/Ti-felt (ca 60 mA mg_Pt⁻¹, accordingly) make these electrodes good candidates for MOR anodes and/or reactive Gas Diffusion Layer Electrodes (GDLEs) in DMFCs and/or methanol electrolysis cells.     

Facile Synthesis of PdCu Echinus‐Like Nanocrystals as Robust Electrocatalysts for Methanol Oxidation Reaction

Exploiting high‐performance and inexpensive electrocatalysts for methanol electro‐oxidation is conductive to promoting the commercial application of direct methanol fuel cells. Here, we present a facile synthesis of echinus‐like PdCu nanocrystals (NCs) via a one‐step and template‐free method. The echinus‐like PdCu NCs possess numerous straight and long branches which can provide abundant catalytic active sites. Owing to the novel nanoarchitecture and electronic effect of the PdCu alloy, the echinus‐like PdCu NCs display high electrocatalytic performance toward methanol oxidation reaction in an alkaline medium. The mass activity of echinus‐like PdCu NCs is 1202.1 mA mg_Pd^?1, which is 3.7 times that of Pd/C catalysts. In addition, the echinus‐like structure, as a kind of three‐dimensional self‐supported nanoarchitecture, endows PdCu NCs with significantly enhanced stability and durability. Hence, the echinus‐like PdCu NCs hold prospect of being employed as electrocatalysts for direct alcohol fuel cells.     

Porous Ni@Pt Core‐Shell Nanotube Array Electrocatalyst with High Activity and Stability for Methanol Oxidation

Bimetallic core‐shell nanostructures are emerging as more important materials than monometallic nanostructures, and have much more interesting potential applications in various fields, including catalysis and electronics. In this work, we demonstrate the facile synthesis of core‐shell nanotube array catalysts consisting of Pt thin layers as the shells and Ni nanotubes as the cores. The porous Ni@Pt core‐shell nanotube arrays were fabricated by ZnO nanorod‐array template‐assisted electrodeposition, and they represent a new class of nanostructures with a high electrochemically active surface area of 50.08 m² (g Pt)^?1, which is close to the value of 59.44 m² (g Pt)^?1 for commercial Pt/C catalysts. The porous Ni@Pt core‐shell nanotube arrays also show markedly enhanced electrocatalytic activity and stability for methanol oxidation compared with the commercial Pt/C catalysts. The attractive performances exhibited by these prepared porous Ni@Pt core‐shell nanotube arrays make them promising candidates as future high‐performance catalysts for methanol electrooxidation. The facile method described herein is suitable for large‐scale, low‐cost production, and significantly lowers the Pt loading, and thus, the cost of the catalysts.     

Preparation of disk‐like Pt/CeO2‐p‐TiO2 catalyst derived from MIL‐125(Ti) for excellent catalytic performance

A feasible strategy is reported for the synthesis of a disk‐like Pt/CeO₂‐p‐TiO₂ catalyst derived from the titanium‐based metal–organic framework (MOF) MIL‐125(Ti) through a few valid steps. To verify the successful synthesis and structural features of the Pt/CeO₂‐p‐TiO₂ catalyst, as‐prepared samples were characterized using several techniques. The characterizations demonstrated that MOF‐derived porous TiO₂ was appropriate for application as a support owing to its moderate surface area (101 m² g^?1) and suitable pore size (6 nm). Moreover, to study the effect of calcination temperature on the catalytic performance, the obtained catalyst was calcined at various temperatures. It was found that Pt/CeO₂‐p‐TiO₂ calcined at 550 °C exhibited the highest catalytic performance, evaluated by means of the reduction of 4‐nitrophenol monitored by UV–visible spectra. Furthermore, this catalyst showed good reusability with a conversion of 94% even after six cycles. Finally, a possible reaction mechanism was proposed to explain the reduction of 4‐nitrophenol to 4‐aminophenol over the Pt/CeO₂‐p‐TiO₂ catalyst.     

Bi‐Microporous Metal–Organic Frameworks with Cubane [M4(OH)4] (M=Ni,Co) Clusters and Pore‐Space Partition for Electrocatalytic Methanol Oxidation Reaction

Embedding cubane [M₄(OH)₄] (M=Ni, Co) clusters within the matrix of metal–organic frameworks (MOFs) is a strategy to develop materials with unprecedented synergistic properties. Herein, a new material type based on the pore‐space partition of the cubic primitive minimal‐surface net (MOF‐14‐type) has been realized. CTGU‐15 made from the [Ni₄(OH)₄] cluster not only has very high BET surface area (3537 m² g^?1), but also exhibits bi‐microporous features with well‐defined micropores at 0.86 nm and 1.51 nm. Furthermore, CTGU‐15 is stable even under high pH (0.1 m KOH), making it well suited for methanol oxidation in basic medium. The optimal hybrid catalyst KB&CTGU‐15 (1:2) made from ketjen black (KB) and CTGU‐15 exhibits an outstanding performance with a high mass specific peak current of 527 mA mg^?1 and excellent peak current density (29.8 mA cm^?2) at low potential (0.6 V). The isostructural cobalt structure (CTGU‐16) has also been synthesized, further expanding the application potential of this material type.     

Facile Hydrogen‐Bond‐Assisted Polymerization and Immobilization Method to Synthesize Hierarchical Fe3O4@Poly(4‐vinylpyridine‐co‐divinylbenzene)@Au Nanostructures and Their Catalytic Applications

Hierarchical Fe₃O₄@poly(4‐vinylpyridine‐co‐divinylbenzene)@Au (Fe₃O₄@P(4‐VP–DVB)@Au) nanostructures were fabricated successfully by means of a facile two‐step synthesis process. In this study, well‐defined core–shell Fe₃O₄@P(4‐VP–DVB) microspheres were first prepared with a simple polymerization method, in which 4‐VP was easily polymerized on the surface of Fe₃O₄ nanoparticles by means of strong hydrogen‐bond interactions between ? COOH groups on poly(acrylic acid)‐modified Fe₃O₄ nanoparticles and a 4‐VP monomer. HAuCl₄ was adsorbed on the chains of a P(4‐VP) shell and then reduced to Au nanoparticles by NaBH₄, which were embedded into the P(4‐VP) shell of the composite microspheres to finally form the Fe₃O₄@P(4‐VP–DVB)@Au nanostructures. The obtained Fe₃O₄@P(4‐VP–DVB)@Au catalysts with different Au loadings were applied in the reduction of 4‐nitrophenol (4‐NP) and exhibited excellent catalytic activity (up to 3025 h^?1 of turnover frequency), facile magnetic separation (up to 31.9 emu g^?1 of specific saturation magnetization), and good durability (over 98 % of conversion of 4‐NP after ten runs of recyclable catalysis and almost negligible leaching of Au).     

Bi‐Microporous Metal–Organic Frameworks with Cubane [M4(OH)4] (M=Ni,Co) Clusters and Pore‐Space Partition for Electrocatalytic Methanol Oxidation Reaction

Embedding cubane [M₄(OH)₄] (M=Ni, Co) clusters within the matrix of metal–organic frameworks (MOFs) is a strategy to develop materials with unprecedented synergistic properties. Herein, a new material type based on the pore‐space partition of the cubic primitive minimal‐surface net (MOF‐14‐type) has been realized. CTGU‐15 made from the [Ni₄(OH)₄] cluster not only has very high BET surface area (3537 m² g^?1), but also exhibits bi‐microporous features with well‐defined micropores at 0.86 nm and 1.51 nm. Furthermore, CTGU‐15 is stable even under high pH (0.1 m KOH), making it well suited for methanol oxidation in basic medium. The optimal hybrid catalyst KB&CTGU‐15 (1:2) made from ketjen black (KB) and CTGU‐15 exhibits an outstanding performance with a high mass specific peak current of 527 mA mg^?1 and excellent peak current density (29.8 mA cm^?2) at low potential (0.6 V). The isostructural cobalt structure (CTGU‐16) has also been synthesized, further expanding the application potential of this material type.     

Revealing the Effect of Surface Composition on Multiwalled Carbon Nanotubes Supported Pt-Fe Alloy Electrocatalysts for Methanol Oxidation Performance

The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt₁Fe₃@NC/MWCNTs catalyst with moderate Fe³⁺ feeding content (0.86 mA/mg_Pt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mg_Pt). Furthermore, the CO oxidation initial potential of Pt₁Fe₃@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt₁Fe₃@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field.     

High‐Performance Electrocatalytic Activity of Palladium‐Copper Nanoalloy towards Methanol Electro‐oxidation in an Alkaline Medium

Nanoalloy of PdCu were synthesized with three different stoichiometry ratio (3 : 1, 1 : 1, 1 : 3) by simple co‐reduction process at 5 °C with Triton X‐100 as surface modifier. Morphology and composition of the synthesized catalyst were characterized by X‐ray diffraction (XRD), X‐ray photo electron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X‐ray analysis (EDAX) with selected area electron diffraction (SAED) techniques. Electrocatalytic activity and stability of the catalysts towards methanol oxidation reaction were verified in alkaline medium by cyclic voltammetry (CV) and chronoamperometry (CA). Observed results emphasis that PdCu nanoalloy in the 3 : 1 stoichiometric ratio shows better catalytic activity (778.98 mA mg⁻¹) and stability not only in the initial state (93.73 mA mg⁻¹) but also after 1800 s (8.61 mA mg⁻¹) among all other prepared catalysts.     

Preparation of Surfactant-Free Pt and PtRu Nanoparticles with High Activity for Methanol Oxidation

A simple and green approach to synthesize highly active electro-catalysts for methanol oxi- dation reaction （MOR） without using any organic agents is described. Pt nanoparticles are directly deposited on the pre-cleaned and pre-oxidized multiwall carbon nanotubes （MWC- NTs） from Pt salt by using CO as the reductant. MOR activity has been characterized by both cyclic voltammetry and chronoamperometry, the current density and mass specific current at the peak potential （ca. 0.9 V vs. RHE） reaches 11.6 mA/cm^2 and 860 mA/mgpt, respectively. After electro-deposition of Ru onto the Pt/MWCNTs surface, the catalysts show steady state mass specific current of 20 and 80 mA/mgpt at 0.5 and 0.6 V, respectively.     

Electroanalytical Study of Methanol Oxidation and Oxygen Reduction at Carbon Nanohorns‐Pt Nanostructured Electrodes

This work reports a comprehensive electroanalytical study of carbon nanohorns (CNHs) in electrochemical applications. Compared to other types of carbons, the bare CNHs electrode exhibited higher peak current densities and lowest anodic peak‐to‐cathodic peak separation of less than 50 mV for the [Fe(CN)^4?]₆/[Fe(CN)^3?]₆ redox couple. Furthermore, CNHs exhibited excellent electrocatalyst supporting properties for porous Pt film towards methanol oxidation reaction reaching a peak current density of 127 mA cm^?2 or peak current mass activity 184 mA mg_Pt^?1. Regarding oxygen reduction reaction, an onset potential as positive as 0. 77 V vs. Ag/AgCl was achieved with CNHs/porous Pt film.     

Ethylene Glycol Electrooxidation Based on Pentangle‐Like PtCu Nanocatalysts

The research of active and stable electrocatalysts toward liquid‐fuel oxidation reaction is of great significance for the large‐scale commercialization of fuel cells. Although extensive efforts have been devoted to pursuing high‐performance nanocatalysts for fuel cells, both the high cost and sluggish reaction kinetics have been two major drawbacks that limited its commercial development. In this regard, we demonstrated a facile solvothermal method for the syntheses of an advanced class of PtCu nanocatalysts with a unique pentangle‐like shape. By combining the merits of a highly active surface area as well as the synergistic and electronic effects, the as‐prepared pentangle‐like Pt₃Cu nanocatalysts showed superior electrocatalytic activity towards ethylene glycol oxidation with a mass and specific activities of 5162.6 mA mg^?1 and 9.7 mA cm^?2, approximately 5.0 and 5.1 times higher than the commercial Pt/C, respectively. More significantly, the Pt₃Cu pentangle also showed excellent long‐term stability with less activity decay and negligible changes in structure after 500 cycles, indicating another class of anode catalysts for fuel cells and beyond.     

Platinum and Palladium Nanotubes Based on Genetically Engineered Elastin–Mimetic Fusion Protein‐Fiber Templates: Synthesis and Application in Lithium‐O2 Batteries

The coupling of proteins with self‐assembly properties and proteins that are capable of recognizing and mineralizing specific inorganic species is a promising strategy for the synthesis of nanoscale materials with controllable morphology and functionality. Herein, GPG‐AG3 protein fibers with both of these properties were constructed and served as templates for the synthesis of Pt and Pd nanotubes. The protein fibers of assembled GPG‐AG3 were more than 10 μm long and had diameters of 20–50 nm. The as‐synthesized Pt and Pd nanotubes were composed of dense layers of ～3–5 nm Pt and Pd nanoparticles. When tested as cathodes in lithium‐O₂ batteries, the porous Pt nanotubes showed low charge potentials of 3.8 V, with round‐trip efficiencies of about 65 % at a current density of 100 mA g^?1.     

Ternary CoPtAu Nanoparticles as a General Catalyst for Highly Efficient Electro‐oxidation of Liquid Fuels

Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO₂. Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1₀‐structure and Au segregates on the surface to alloy with Pt. The L1₀‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg_Pt, 1.49 A/mg_Pt, and 11.97 A/mg_Pt, respectively in 0.1 m HClO₄. The L1₀‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C?C bond more efficiently for ethanol oxidation.     

Two‐Dimensional Conjugated Aromatic Networks as High‐Site‐Density and Single‐Atom Electrocatalysts for the Oxygen Reduction Reaction

Two‐dimensional conjugated aromatic networks (CAN) with ultra‐thin conjugated layers (ca. 3.5 nm) and high single‐metal‐atom‐site density (mass content of 10.7 wt %, and 0.73 metal atoms per nm²) are prepared via a facile pyrolysis‐free route involving a one‐step ball milling of the solid‐phase‐synthesized polyphthalocyanine. These materials display outstanding oxygen reduction reaction (ORR) mass activity of 47 mA mg_cat.^?1 represents 1.3‐ and 6.4‐fold enhancements compared to Pt and Pt/C in benchmark Pt/C, respectively. Moreover, the primary Zn‐air batteries constructed with CAN as an air electrode demonstrate a mass/volume power density of 880 W g_cat.^?1/615 W cm_cat.^?3 and stable long‐term operation for 100 h. This strategy offers a new way to design high‐performance electrocatalysts with atomic precision for use in other energy‐storage and conversion applications.     

A Versatile Iron–Tannin‐Framework Ink Coating Strategy to Fabricate Biomass‐Derived Iron Carbide/Fe‐N‐Carbon Catalysts for Efficient Oxygen Reduction

The conversion of biomass into valuable carbon composites as efficient non‐precious metal oxygen‐reduction electrocatalysts is attractive for the development of commercially viable polymer electrolyte membrane fuel‐cell technology. Herein, a versatile iron–tannin‐framework ink coating strategy is developed to fabricate cellulose‐derived Fe₃C/Fe‐N‐C catalysts using commercial filter paper, tissue, or cotton as a carbon source, an iron–tannin framework as an iron source, and dicyandiamide as a nitrogen source. The oxygen reduction performance of the resultant Fe₃C/Fe‐N‐C catalysts shows a high onset potential (i.e. 0.98 V vs the reversible hydrogen electrode (RHE)), and large kinetic current density normalized to both geometric electrode area and mass of catalysts (6.4 mA cm^?2 and 32 mA mg^?1 at 0.80 V vs RHE) in alkaline condition. This method can even be used to prepare efficient catalysts using waste carbon sources, such as used polyurethane foam.