Synthesis of ultrafine Pt nanoparticles stabilized by pristine graphene nanosheets for electro-oxidation of methanol

Platinum Species on Oxygen Vacancy-Rich Titania for Efficient Basic Electrocatalytic Hydrogen Evolution

Oxygen vacancy-rich titania is a promising support for enhancing the hydrogen evolution reaction (HER). This work innovatively loaded Pt nanoparticles on oxygen vacancy-rich TiO2 (Pt/Vo-TiO2) in situ by using a photocatalytic device. The synthesis conditions are mild, do not require high temperatures and strong reducing agents, and can avoid the accumulation of platinum species. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectrometry (XAS) verified the synergistic effect of Pt species and oxygen vacancies on the progress of the reaction kinetics, where the Pt particles exposed by the in situ synthesis functioned as reaction sites in the electrocatalytic hydrogen evolution. Based on this, Pt/Vo-TiO2 exhibits excellent electrocatalytic performance with an overpotential of only 56 mV at a current density of 10 mA cm-2 and a Tafel slope of only 73.5 mV dec-1. This work provides a new strategy for designing highly efficient HER catalysts.

Enhanced Methanol Electro-Oxidation Activity of Nanoclustered Gold

Size-selected 3 nm gas-phase Au clusters dispersed by cluster beam deposition (CBD) on a conducting fluorine-doped tin oxide template show strong enhancement in mass activity for the methanol electro-oxidation (MEO) reaction compared to previously reported nanostructured gold electrodes. Density functional theory-based modeling on the corresponding Au clusters guided by experiments attributes this high MEO activity to the high density of exposed under-coordinated Au atoms at their faceted surface. In the description of the activity trends, vertices and edges are the most active sites due to their favorable CO and OH adsorption energies. The faceted structures occurring in this size range, partly preserved upon deposition, may also prevent destructive restructuring during the oxidation-reduction cycle. These results highlight the benefits of using CBD in fine-tuning material properties on the nanoscale and designing high-performance fuel cell electrodes with less material usage.

A facile solvothermal synthesis of Pt1.2Co/C bimetallic nanocrystals as efficient electrocatalysts for methanol oxidation and hydrogen evolution reaction

A bimetallic alloyed Pt_1.2Co/C catalyst, which exhibited superior electrocatalytic performance for both MOR and HER, was synthesized by a one-pot solvothermal approach.

Atomic Carbon Layers Supported Pt Nanoparticles for Minimized CO Poisoning and Maximized Methanol Oxidation

Maximizing activity of Pt catalysts toward methanol oxidation reaction (MOR) together with minimized poisoning of adsorbed CO during MOR still remains a big challenge. In the present work, uniform and well-distributed Pt nanoparticles (NPs) grown on an atomic carbon layer, that is in situ formed by means of dry-etching of silicon carbide nanoparticles (SiC NPs) with CCl₄ gas, are explored as potential catalysts for MOR. Significantly, as-synthesized catalysts exhibit remarkably higher MOR catalytic activity (e.g., 647.63 mA mg^-1 at a peak potential of 0.85 V vs RHE) and much improved anti-CO poisoning ability than the commercial Pt/C catalysts, Pt/carbon nanotubes, and Pt/graphene catalysts. Moreover, the amount of expensive Pt is a few times lower than that of the commercial and reported catalyst systems. As confirmed from density functional theory (DFT) calculations and X-ray absorption fine structure (XAFS) measurements, such high performance is due to reduced adsorption energy of CO on the Pt NPs and an increased amount of adsorbed energy OH species that remove adsorbed CO fast and efficiently. Therefore, these catalysts can be utilized for the development of large-scale and industry-orientated direct methanol fuel cells.

Enhanced Photoinduced Electrocatalytic Oxidation of Methanol Using Pt Nanoparticle-Decorated TiO2-Polyaniline Ternary Nanofibers

Herein, perylene-3,4,9,10-tetracarboxylic acid-doped polyaniline (PTP) nanofibers with/without photoreactive anatase TiO₂ (TiO₂-PTP and PTP, respectively) have been successively synthesized and subsequently decorated by Pt nanoparticles (Pt NPs) to prepare Pt-PTP and Pt-TiO₂-PTP composites. High-resolution transmission electron microscopy confirms the presence of ∼3 nm spherical-shaped Pt NPs on both the composites along with TiO₂ on Pt-TiO₂-PTP. Pt loading on the composites is deliberately kept similar to compare the methanol electro-oxidation in the two composites. The Pt nanocomposites along with the precursor polyanilines are characterized by optical characterization, X-ray diffraction study, X-ray fluorescence spectroscopy, and Raman spectroscopy. The ternary composite-modified (Pt-TiO₂-PTP) electrode demonstrates high electrocatalytic performance for methanol oxidation reaction in acid medium than Pt-PTP and Pt-TiO₂. The higher electrochemical surface area (1.7 times), high forward/backward current ratio, and the higher CO tolerance ability for Pt-TiO₂-PTP make it a superior catalyst for methanol oxidation reaction in the electrochemical process than Pt-PTP. Moreover, the catalytic activity of Pt-TiO₂-PTP is further enhanced significantly with light irradiation. The cooperative effects of photo- and electrocatalysis on methanol oxidation reaction in Pt-TiO₂-PTP enhance the methanol oxidation catalytic activity approximately 1.3 times higher in light illumination than in dark. Therefore, the present work will be proficient to get a light-assisted sustainable approach for developing the methanol oxidation reaction activity of Pt NP-containing catalysts in direct methanol fuel cells.

Nanostructure Optimization of Platinum-Based Nanomaterials for Catalytic Applications

Platinum-based nanomaterials have attracted much interest for their promising potentials in fields of energy-related and environmental catalysis. Designing and controlling the surface/interface structure of platinum-based nanomaterials at the atomic scale and understanding the structure-property relationship have great significance for optimizing the performances in practical catalytic applications. In this review, the strategies to obtain platinum-based catalysts with fantastic activity and great stability by composition regulation, shape control, three-dimension structure construction, and anchoring onto supports, are presented in detail. Moreover, the structure-property relationship of platinum-based nanomaterials are also exhibited, and a brief outlook are given on the challenges and possible solutions in future development of platinum-based nanomaterials towards catalytic reactions.

Exceptional Electrocatalytic Activity and Selectivity of Platinum@Nitrogen-Doped Mesoporous Carbon Nanospheres for Alcohol Oxidation

Porous carbon materials have attracted considerable attention for their various applications such as catalyst supports for fuel cells. However, few studies focus on the effect of carbon pore structure on different alcohols electrooxidation. In this work, platinum@nitrogen-doped carbon nanospheres with tailored mesopores (Pt@NMCs) are fabricated and exhibit outstanding electrocatalytic activity and durability for alcohol oxidation because of the structural advantages such as adjustable mesopores, N-doped carbon, and embedded catalysts. More importantly, the pore size of NMCs (or called the size of the windows connecting the neighboring spherical cavities), which can be tuned simply by adjusting the diameter of colloidal silica nanospheres, has a great effect on the electrocatalytic activity and selectivity of Pt catalysts toward oxidation of alcohols (methanol, ethanol, and n-propanol). Accordingly, we can adopt optimal Pt@NMCs with appropriate pore size based on different requirements and applications.

Superior alkaline hydrogen evolution electrocatalysis enabled by an ultrafine PtNi nanoparticle-decorated Ni nanoarray with ultralow Pt loading

An ultrafine PtNi nanoparticle-decorated Ni nanosheet array with ultralow Pt loading acts as a superior hydrogen-evolving electrocatalyst.

Synthesis of Ultrasmall Platinum Nanoparticles on Polymer Nanoshells for Size-Dependent Catalytic Oxidation Reactions

It is highly desirable for the synthesis and stabilization of noble metal nanoparticles of uniform, precisely tunable sizes, especially in the range of angstroms to a few nanometers, for many catalytic applications in pursuit of optimal activity and selectivity. Herein, we report a novel strategy for the synthesis of uniform platinum (Pt) nanoparticles of ultrasmall sizes (average size: 0.9-2.3 nm), which are stabilized on hollow polymer nanoshells formed by polymerization of sodium dodecyl benzenesulfonate (SDBS) at the interface of an ethanol/water emulsion. The resulting composite represents a highly active catalyst for effective oxidation of alcohols under ambient conditions. Strong size-dependent catalytic activity of Pt nanoparticles has been revealed in aerobic oxidation of 1-phenylethanol to yield acetophenone, demonstrating a volcano-shape profile, with Pt nanoparticles of ∼1.7 nm showing the highest activity. The size effect has been attributed to the size-dependent d-band electron structure of the Pt nanoparticles. This work reveals the size effect of Pt nanoparticles in general organic oxidation reactions, and thus provides a general methodology and a lot of opportunities in the design of metal-nanoparticle-based catalysts for fine-chemical production.

In Situ Assembly of Ultrathin PtRh Nanowires to Graphene Nanosheets as Highly Efficient Electrocatalysts for the Oxidation of Ethanol

One-dimensional (1D) anisotropic platinum-based nanowires are promising electrocatalysts in polymer electrolyte membrane fuel cells owing to the inherent structural merits. Herein, we report an in situ growth of ultrathin PtRh nanowires (diameters of 2-3 nm) on graphene nanosheets via the oriented attachment pathway. Mechanistic studies reveal that graphene nanosheets play a critical role in the nucleation and growth of PtRh nanowires. The resulting hybrid of PtRh nanowire decorated graphene nanosheets shows outstanding activity and durability toward ethanol electro-oxidation. It exhibits a specific current density of 2.8 mA cm^-2 and a mass-normalized current density of 1 A mg^-1 metal, which are 5.4 and 3.1 times those of the state-of-the-art Pt/C catalyst, respectively. After 2000 cyclic tests, it maintains 86% of the initial electrochemically active surface area, which is larger than that of 63% obtained from the Pt/C catalyst. The superior performance is attributed to the combination of the advantageous 1D morphological motif with the synergistic effects of PtRh alloys and graphene nanosheet support.

Synergistically Improving the Activity, Antipoisonous Ability, and Long-Term Stability of Pt to Methanol Oxidation through Developing Favorable Graphene-Based Supports

An interconnected framework of reduced graphene oxide/phenyl formaldehyde polymer composites was synthesized by a one-pot hydrothermal reaction followed by carbonizing under different conditions. Then, the obtained porous materials with varied surface properties were used to disperse ultrasmall Pt nanoparticles. The catalyst with the optimized support demonstrates superior achievements to methanol oxidation reaction (MOR): distinctive improved mass activity (MA) and specific activity at both forward peak position and at the potential range near the operation of fuel cells, best antipoisonous ability revealed by 17 times MA and 7 times the retaining rate of commercial Pt/C in chronoamperometric evaluations, and outstanding long-term stability verified by 3-4 times MA and the retaining rate of Pt/C in the accelerated duration tests. By analyzing the performances of all studied catalysts, we proposed that fruitful oxygen groups and defects on the surface of supporting materials play a key role in boosting the MOR fulfillments through strengthening the Pt-substrate interaction or facilitating the removal of CO from the Pt surface. Elimination of surface oxygen groups and defects may promote the conductivity and mechanical strength of the catalysts but could result in a serious deterioration of antipoisonous ability, which means that only if the deliberate balance is achieved in the preparation of supporting materials can the MOR performances of Pt be improved synergistically.

Self-Decoration of PtNi Alloy Nanoparticles on Multiwalled Carbon Nanotubes for Highly Efficient Methanol Electro-Oxidation

ABSTRACT

A simple one-pot method was developed to prepare PtNi alloy nanoparticles, which can be self-decorated on multiwalled carbon nanotubes in [BMIm][BF4] ionic liquid. The nanohybrids are targeting stable nanocatalysts for fuel cell applications. The sizes of the supported PtNi nanoparticles are uniform and as small as 1-2 nm. Pt-to-Ni ratio was controllable by simply selecting a PtNi alloy target. The alloy nanoparticles with Pt-to-Ni ratio of 1:1 show high catalytic activity and stability for methanol electro-oxidation. The performance is much higher compared with those of both Pt-only nanoparticles and commercial Pt/C catalyst. The electronic structure characterization on the PtNi nanoparticles demonstrates that the electrons are transferred from Ni to Pt, which can suppress the CO poisoning effect.

GRAPHICAL ABSTRACT

Ternary Platinum-Copper-Nickel Nanoparticles Anchored to Hierarchical Carbon Supports as Free-Standing Hydrogen Evolution Electrodes

Developing cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts for hydrogen production is of paramount importance to attain a sustainable energy future. Reported herein is a novel three-dimensional hierarchical architectured electrocatalyst, consisting of platinum-copper-nickel nanoparticles-decorated carbon nanofiber arrays, which are conformally assembled on carbon felt fabrics (PtCuNi/CNF@CF) by an ambient-pressure chemical vapor deposition coupled with a spontaneous galvanic replacement reaction. The free-standing PtCuNi/CNF@CF monolith exhibits high porosities, a well-defined geometry shape, outstanding electron conductivity, and a unique characteristic of localizing platinum-copper-nickel nanoparticles in the tips of carbon nanofibers. Such features render PtCuNi/CNF@CF as an ideal binder-free HER electrode for hydrogen production. Electrochemical measurements demonstrate that the PtCuNi/CNF@CF possesses superior intrinsic activity as well as mass-specific activity in comparison with the state-of-the-art Pt/C catalysts, both in acidic and alkaline solutions. With well-tuned composition of active nanoparticles, Pt42Cu57Ni1/CNF@CF showed excellent durability. The synthesis strategy reported in this work is likely to pave a new route for fabricating free-standing hierarchical electrodes for electrochemical devices.

Controllable synthesis of Ni(OH)2/Co(OH)2 hollow nanohexagons wrapped in reduced graphene oxide for supercapacitors

Reduced graphene oxide (rGO) wrapped hollow nanohexagons comprised of nickel hydroxide and cobalt hydroxide have been synthesized via in situ wet chemical approach.

Highly Dispersed Ultrafine Pt Nanoparticles on Reduced Graphene Oxide Nanosheets: In Situ Sacrificial Template Synthesis and Superior Electrocatalytic Performance for Methanol Oxidation

We report a simple and environmentally friendly route to prepare platinum/reduced graphene oxide (Pt/rGO) nanocomposites (NCs) with highly reactive MnOx colloids as reducing agents and sacrificial templates. The colloids are obtained by laser ablation of a metallic Mn target in graphene oxide (GO)-containing solution. Structural and morphological investigations of the as-prepared NCs revealed that ultrafine Pt nanoparticles (NPs) with an average size of 1.8 (±0.6) nm are uniformly dispersed on the surfaces of rGO nanosheets. Compared with commercial Pt/C catalysts, Pt/rGO NCs with highly electrochemically active surface areas show remarkably improved catalytic activity and durability toward methanol oxidation. All of these superior characteristics can be attributed to the small particle size and uniform distribution of the Pt NPs, as well as the excellent electrical conductivity and stability of the rGO catalyst support. These findings suggest that Pt/rGO electrocatalysts are promising candidate materials for practical use in fuel cells.

Monolayer of close-packed Pt nanocrystals on a reduced graphene oxide (RGO) nanosheet and its enhanced catalytic performance towards methanol electrooxidation

A close-packed monolayer composed of (111)-orientated Pt nanocrystals was fabricated on reduced graphene oxide, exhibiting excellent electrocatalytic activity and stability towards methanol oxidation, ~3 times better mass activity than the commercial Pt/C.

Effect of size and oxidation state of platinum nanoparticles on the electrocatalytic performance of graphene-nanoparticle composites

Size and oxidation state of Pt nanoparticles significantly influence the electrocatalytic performance of Pt–graphene nanocomposites for methanol oxidation and 2.2 nm Pt with variable oxidation states offers the best catalytic activity and durability.

Human hair-derived graphene-like carbon nanosheets to support Pt nanoparticles for direct methanol fuel cell application

A novel graphene-like carbon nanosheet (HGCN) with high specific surface area and multimodal pore system was synthesized using human hair as a carbon source for the deposition of PtNPs.