PtCu Alloy Research Articles

On the viability of chitosan-derived mesoporous carbons as supports for PtCu electrocatalysts in PEMFC

Chitosan is an abundant and non-toxic natural polysaccharide rich in nitrogen, which is used here to obtain N-doped mesoporous carbons (NMCs) as supports for Pt-saving PtCu alloy elecrocatalysts, which can be of interest for low-temperature fuels cells. NMCs with different textural properties were synthesized from cheap silica templates. They presented relative dominance of disordered graphitic lattice and comparable amounts of pyrrolic and pyridinic N, with different specific BET surface areas (715–1040 m2 g−1) and mesopore (1.2–2.4 cm3 g−1) and micropore volumes (0.1–0.6 cm3 g−1). PtCu nanoparticles were deposited by Cu electroless deposition and further galvanic exchange with Pt, with overall Pt loadings about 20 wt.%. Pt-rich PtCu alloy crystallites with contracted Pt fcc lattices and sizes of 3.1–4.7 nm were formed. The synthesized PtCu/NMCs catalysts presented better specific current densities for the oxygen reduction and better CO tolerance and specific current densities for the methanol oxidation reaction than those of commercial Pt/C and PtCu/CMK-3. The PtCu/NMC prepared with the H2SO4–activated NMC was the most active catalyst. The different textural properties of the carbonaceous materials appeared to determine the surface structure of the PtCu nanoparticles.

MXene-reinforced octahedral PtCu nanocages with boosted electrocatalytic performance towards endocrine disrupting pollutants sensing.

Rational tailoring of hollow and porous bimetallic structures with excellent electrocatalytic performance is appealing yet challenging. Further, combining independent bimetallic nanoparticles with flexible two-dimensional substrate by forming stable heterocomplex is still highly desired for electrocatalysis. Herein, hierarchical PtCu alloy octahedrons with hollow interiors and nanosheet-assembled nanoshells were synthesized by a facile and efficient chemical transformation strategy using Cu2O as sacrificial templates. Such octahedral PtCu nanocages displayed significantly enhanced electrocatalytic activity owing to their unique hollow and porous architectures which provided easy access for analytes to the catalyst surface. Thereafter, introduction of Ti3C2Tx MXene was realized via simple incubation of Ti3C2Tx in solution containing the 3-aminopropyltriethoxysilane-capped PtCu, and their electrostatic interaction guaranteed the firm adsorption of PtCu nanocages on Ti3C2Tx nanosheets. It turned out that the sensitivity of the hybrid sensor was remarkably improved for electrochemical monitoring of endocrine disrupting pollutants in water, exhibiting ultrawide linear ranges and sub-nanomole detection limits. The eminent electrode performance is attributed to the high specific area, fast electrochemical kinetics, decent electrical catalytic ability, and the synergistic effect between Pt, Cu, and MXene.

Study on ethanol electro-oxidation over a carbon-supported Pt-Cu alloy catalyst by pinhole on-line electrochemical mass spectrometry.

A carbon supported Pt-Cu electrocatalyst was synthesized by the microwave-polyol method following acid-treatment and physically characterized by different techniques including X-ray diffraction (XRD) and transmission electron microscopy (TEM). Both potentiodynamic and potentiostatic measurements with pinhole on-line electrochemical mass spectrometry were carried out to study the electrocatalytic activity and reaction intermediates of Pt/C and Pt-Cu/C electrocatalysts during the ethanol oxidation reaction. The results of potentiodynamic and potentiostatic measurements showed that the Pt-Cu/C electrocatalyst has higher ethanol oxidation efficiency and incomplete ethanol oxidation to acetaldehyde and acetic acid prevails under the given conditions. After calibration of the m/z = 44 mass signal, the CO2 current efficiencies on Pt/C and PtCu-3/C were ∼7% and ∼12%, respectively, which reveal that the presence of copper enhances the complete ethanol oxidation to CO2.

Dendritic Plasmonic CuPt Alloys for Closed-Loop Multimode Cancer Therapy with Remarkably Enhanced Efficacy.

The outcome of laser-triggered plasmons-induced phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is significantly limited by the hypoxic tumor microenvironment and the upregulation of heat shock proteins (HSPs) in response to heat stress. Mitochondria, the biological battery of cells, can serve as an important breakthrough to overcome these obstacles. Herein, dendritic triangular pyramidal plasmonic CuPt alloys loaded with heat-sensitive NO donor N, N'-di-sec-butyl-N, N'-dinitroso-1,4-phenylenediamine (BNN) is developed. Under 808nm laser irradiation, plasmonic CuPt can generate superoxide anion free radicals (·O2 - ) and heat simultaneously. The heat generated can then trigger the release of NO gas, which not only enables gas therapy but also damages the mitochondrial respiratory chain. Impaired mitochondrial respiration leads to reduced oxygen consumption and insufficient intracellular ATP supply, which effectively alleviates tumor hypoxia and undermines the synthesis of HSPs, in turn boosting plasmonic CuPt-based PDT and mild PTT. Additionally, the generated NO and ·O2 - can react to form more cytotoxic peroxynitrite (ONOO- ). This work describes aplasmonic CuPt@BNN (CPB) triggered closed-loop NO gas, free radicals, and mild photothermal therapy strategy that is highly effective at reciprocally promoting antitumor outcomes.

Enhanced ammonia sensitivity electrochemical sensors based on PtCu alloy nanoparticles in-situ synthesized on carbon cloth electrode

The alloying of Pt with transition metals is significant in boosting the performance of Pt-based electrochemical sensors. In this paper, Platinum and copper alloy nanoparticles (PtCu NPs) were in-situ loaded on carbon cloth (CC) by electrochemical deposition to obtain a self-supported electrode (PtCu-CC) for electrochemical detection of ammonia. The alloying of Pt and Cu reduced the crystal lattice spacing of Pt and improved the catalytic performance of ammonia. Therefore, the PtCu-CC electrode displayed visibly enhanced ammonia detection performance compared with the Pt-CC electrode and commercial Pt electrode. The linear range for ammonia determination was from 0.5 to 40 and 40–500 μM, and the sensitivity of the Pt7Cu1-CC sensor was 9.5 μA μM−1 cm−2 and 0.778 mA lg μM−1 cm−2, respectively. The detection limit was 8.6 ± 0.32 nM, and the quantification limit was 28.67 ± 0.73 nM. The developed sensor shows good anti-interference capability, reproducibility and stability; in addition, it exhibited good capacity in the actual water sample test. PtCu alloy nanoparticles were applied to ammonia detection in water, which may broaden the ways of ammonia detection in water.

Structural evolution of PtCu nanoframe for efficient oxygen reduction reactions

• Synthesis of high-active PtCu nanoframes for oxygen reduction reaction. • Synergistic interaction of PtCu nanoframes has excellent electrocatalytic performance. • The etched PtCu nanoframes shows high stability in durability tests. Advances in proton exchange membrane fuel cells require Pt-based catalysts with high catalytic activity and stability. However, due to the expensiveness of Pt, scholars are mainly finding ways to improve the catalytic performance and decrease Pt usage. In this paper, the synthesis of high-active PtCu alloy nanoframes is reported. The nanoframes are prepared by the electric displacement reaction between the Cu nanoplate (Cu NP) template and the Pt precursor, and the high-active PtCu alloy nanoframes are obtained by further etching. The synergistic effect of alloy PtCu nanoframes shows excellent electrocatalytic performance for oxygen reduction reactions, with PtCu high-active nanoframes(PtCu HNF) having approximately 1.4 times the mass activity of commercial Pt/C and exhibiting high stability and tolerance in acidic ORR. Due to the increase in the number of surface active sites and the synergistic effect of bimetals, the activity and stability of the catalyst are significantly improved.

Hot Carrier Lifetimes and Electrochemical Water Dissociation Enhanced by Nickel Doping of a Plasmonic Electrocatalyst

Hot carriers generated by localized surface plasmon resonance (LSPR) excitation of plasmonic metal nanoparticles are known to enhance electrocatalytic reactions. However, the participation of plasmonically generated carriers in interfacial electrochemical reactions is often limited by fast relaxation of these carriers. Herein, we address this challenge by tuning the electronic structure of a plasmonic electrocatalyst. Specifically, we design an electrocatalyst for alkaline hydrogen evolution reaction (HER) that consists of nanoparticles of a ternary Cu-Pt-Ni ternary alloy. The CuPt alloy has both plasmonic attributes and electrocatalytic HER activity. Ni doping contributes an electron-deficient 3d band and fully filled 4s band, which promotes water adsorption and prolongs the lifetimes of excited carriers generated by plasmonic excitation. As an outcome, the Cu-Pt-Ni nanoparticles exhibit boosted activity for electrochemical water dissociation and HER under LSPR excitation.

Ordered Intermetallic PtCu Catalysts Made from Pt@Cu Core/Shell Structures for Oxygen Reduction Reaction.

Platinum-based ordered intermetallic compounds are promising low-Pt catalysts toward the oxygen reduction reaction (ORR) for high-performance fuel cells. However, the synthesis of ordered intermetallic catalysts usually requires high-temperature annealing to overcome the energy barrier for atom diffusion, which leads to inevitable sintering of catalysts and greatly reduced mass-specific activity. Herein, we developed a new strategy to synthesize PtCu-ordered intermetallic catalysts by the generation of the Pt@Cu core/shell nanoparticles (Pt@Cu NPs) by Pt-assisted H2 reduction of Cu2+ with subsequent annealing at 500-1000 °C. Compared to the commonly used wet-impregnation method, the core/shell structure starts to form ordered PtCu alloys at a lower annealing temperature (500 °C). The Pt@Cu core/shell structure avoids the necessary process of Cu atoms diffusing to Pt NPs across the carbon supports occurred during high-temperature annealing in the wet-impregnation method, which ensures the formation of PtCu NPs with higher ordering degree while annealing at the same temperature. The highly ordered small-sized PtCu catalysts prepared by the core/shell strategy exhibit higher mass activity and specific activity compared to those prepared by the wet-impregnation method. Moreover, a positive correlation between the ORR activity and the ordering degree of the intermetallic PtCu NPs is identified, which could be associated with the increase of compressive strain with the ordering degree.

Light doping of tungsten into copper-platinum nanoalloys for boosting their electrocatalytic performance in methanol oxidation

Coupling the bi-functional mechanism with compressive lattice strain might be an effective way to boost the electrocatalysis of platinum (Pt)-based nanoparticles for methanol oxidation reaction (MOR). This strategy weakens the chemisorption of poisoning CO-like intermediates generated during MOR on the active Pt sites by lowering their d-band center. In this context, we herein report the synthesis of ternary copper-tungsten-platinum (CuWPt) nanoalloys with light doping of W element by simply co-reducing their precursors at elevated temperature. In this ternary alloy system, the presence of only small amount of W element not only weakens the chemisorption of CO-like intermediates by lowering the Pt d-band center through compressive lattice strain, but also cleans the active Pt sites by "hydrogen spillover effect", endowing the as-prepared CuWPt nanoalloys at an appropriate Cu/W/Pt ratio with good activity for MOR. In specific, the ternary CuWPt alloy nanoparticles at a Cu/W/Pt molar ratio of 21/4/75 show a specific activity of 2.5 mA·cm⁻² and a mass activity of 2.11 A·mg⁻¹ with a better durability, outperforming those ternary CuWPt alloy nanoparticles at other Cu/W/Pt ratios, binary CuPt alloys and commercial Pt/C catalyst as well as a large number of reported Pt-based electrocatalysts. In addition, a single direct methanol fuel cell (DMFC) assembled using ternary CuWPt nanoalloys as anodic catalysts shows a power density of 24.3 mW·cm⁻² and an open-circle voltage of 0.6 V, also much higher than those of the single DMFC assembled from commercial Pt/C catalysts.

Boosting catalytic stability for VOCs removal by constructing PtCu alloy structure with superior oxygen activation behavior

The elimination of volatile organic compounds (VOCs) emitted from the process of industry production is of great significance to improve the atmospheric environment. Herein the catalytic oxidation of the toluene and iso-hexane mixture, as the typical components from furniture paint industry, and the enhancement in the catalytic stability for toluene oxidation were investigated in detail. The formation rate of active oxygen species was very important for the development of the catalyst with high catalytic stability. Compared with the Pt/M catalyst, the Pt-Cu/M catalyst owned stronger ability of VOCs adsorption and gaseous oxygen activation by introducing additional sites for activating O2. The Langmuir–Hinshelwood (adsorbed oxygen) and Mars–van Krevelen (lattice oxygen) mechanism existed in toluene oxidation over the present Pt/M and Pt-Cu/M catalysts, respectively. The change in the involved active oxygen species during toluene oxidation was resulted from the Pt-Cu alloy structure. In addition to the adsorption of O2, a part of active lattice oxygen species can also be replenished by the migration of bulk lattice oxygen over Pt-Cu/M. With a rise in the reaction temperature, weakly adsorbed iso-hexane could be timely reacted with the more active lattice oxygen species to keep the catalytic stability over the Pt/M and Pt-Cu/M catalysts. Generally, we not only prepared a promising material for the catalytic removal of VOCs from the furniture paint industry, but also provided a new strategy for the generation of active oxygen species, making the catalyst exhibit high catalytic oxidation stability.

(Invited) Investigations into the Role of Adsorption Processes in Alloy Deposition

The interplay between adsorption, underpotential deposition and excess bond enthalpy in the deposition of alloys and intermetallic will be discussed based on selections from recent work. Examples of limiting behavior will be presented that range from the deposition of solid-solutions, e.g. Pt-Cu and Pt-Fe group alloys, to intermetallics, e.g. Pt-Pb, to immiscible, e.g. Cu-Pb, systems. In addition, the impact of “parasitic” reactions, such as electrolyte breakdown, on the deposition of elements and alloys will be briefly discussed. The utility of a close coupling between electroanalytical, gravimetric, metallurgical and surface science measurements to reveal the underlying thermodynamic and kinetic influences on co-deposition process will be highlighted.

In Situ Surface PtCu Alloying on Delafossite-type CuAlO2 as Electrocatalyst for Enhanced Methanol Oxidation

Delafossite type oxide CuAlO2 as a highly efficient methanol oxidation reaction catalyst support has been investigated in this work. Utilizing the sustained release of copper from CuAlO2 layered structure, we developed a composite catalyst that was in situ formed PtCu alloy upon oxide via solvothermal method. Owing to the metal-support interaction between PtCu alloy and CuAlO2, abundant oxygen defects and adsorbed hydroxyl groups were generated on the surface of composite catalyst, which were verified by structural characterizations and surface analysis. Density functional theory simulation further revealed that the in situ formation of PtCu alloy accompanied with superficial defects dramatically changed the geometry and electronic structures of the composite catalyst, resulting in a higher mass activity (990 mA/mgPt), specific activity (3.30 mA cm−2 ECSA), and a superior reaction kinetics of MOR performance. This work proves delafossite type oxide CuAlO2 as a potential support to facilitate the anti-CO poisoning ability of Pt-based catalysts.

Effects of second metals (M = Fe, Cu, Ga, In, Sn) on the geometric and electronic properties of platinum for the direct dehydrogenation of propane

Supported Pt-based bimetallic catalysts are representative types of dehydrogenation catalysts used for alkanes to olefins conversion. The platinum in these catalysts exhibits unique structural features accompanied with changes in electronic states due to the addition of the second metal. To investigate the impact of each effect on the activity for propane dehydrogenation, a series of Pt-M/SiO 2 (M= Fe, Cu, Ga, In and Sn) catalysts were prepared and used for propane dehydrogenation. Utilizing various characterization techniques, the geometric and electronic properties of these catalysts were studied. The relationships between the specific activity of bimetallic platinum catalysts in propane dehydrogenation and atomic sizes of alloys (i) and the total density of unoccupied d bands in platinum (ii) were considered. Via alloy formation, it was found that dilution of the active metal Pt occurred in these SiO 2 supported bimetallic catalysts, and the lattice parameter of Pt-M alloys decreased on Pt-Fe, Pt-Cu and Pt-Ga alloys, but increased on Pt-In and Pt-Sn alloys when compared with that of Pt foil. Catalytic activity was evidently shown to not be a function of the lattice parameters of Pt-M alloys, but appears closely related with the d -holes of Pt in Pt-M bimetallic catalysts. More d holes show favorably high activity. Among the studied Pt-M/SiO 2 (M= Fe, Cu, Ga, In and Sn) catalysts, the prominent and primary role of the electronic effect was demonstrated. • Mansour’method was used to quantitatively determine the electronic state of Pt. • Pt-Ga/SiO 2 catalyst exhibits biggest d -holes and highest initial conversion of propane. • The electronic effect plays a crucial role in studied systems.

Tuning the surface structure and phase structure of PtCu3 nanoparticle for highly efficient electrocatalysts

Significantly improving the catalytic activity and durability of platinum (Pt) based electrocatalysts is crucial for commercial application of fuel cells by tuning structure of Pt alloy nanoparticles. Here, we report a method of tuning structure of PtCu3 alloy nanoparticle by annealing in different atmospheres. The detailed analyses showed that evolution of surface structure and phase structure of PtCu3 alloy nanoparticles heat-treated in N2 atmosphere and N2/H2 mixed atmosphere are mainly as follows: (1) when heat-treated in N2, the crystal phase of PtCu3 has undergone a transformation from disordered PtCu3 alloy to ordered PtCu3 alloy and then to disordered PtCu3 alloy with the increase of holding time from 30 min to 90 min; (2) when heat-treated in H2/N2, a Pt-rich surface is formed on the Pt–Cu nanoparticles due to Pt segregation induced by H2 adsorption. Electrochemical measurements demonstrated that both PtCu3/C-N2 electrocatalysts prepared in N2 and PtCu3/C-N2/H2 electrocatalysts prepared in H2/N2 exhibit enhanced mass activities toward the oxygen reduction reaction (ORR) relative to Pt/C electrocatalyst in acidic media. In particular, when the holding time is 90 min, the obtained PtCu3/C-N2/H2 electrocatalysts with Pt-rich surface showed highest mass activity of 435 mA/mgPt (at 0.9 V vs. RHE), which is four times greater than that of Pt/C catalyst (20 wt.% Pt, 115 mA/mgPt). This study provides a promising method for the reasonable design and preparation of low cost and high performance Pt-based electrocatalysts.

Geometric Engineering of Porous PtCu Nanotubes with Ultrahigh Methanol Oxidation and Oxygen Reduction Capability.

Platinum (Pt), as a commonly used electrocatalyst in direct methanol fuel cells (DMFCs), suffers from sluggish kinetics of both the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). Geometric engineering has been proven effective for improving the MOR and ORR activities. Thus, by modulating the Pt precursor and poly(vinylpyrrolidone) (PVP) dosages, different porous PtCu nanotubes constructed by hollow nanospheres, solid alloy, and Pt-rich skinned nanoparticles, respectively, are successfully synthesized. Among them, the solid PtCu alloy nanoparticle coherent nanotubes exhibit the specific activity 9.42 times higher than Pt/C toward MOR, while the hollow PtCu alloy nanosphere coherent nanotubes show the specific activity 4.85 times higher than Pt/C toward ORR. The different Pt:Cu ratios of hollow nanospheres, solid alloy, and Pt-rich skinned nanoparticles cause the differences in electron transfer from Cu to Pt as well as electronic structures of Pt. As a result, the binding energies of intermediates can be regulated, leading to the enhancement in MOR and ORR.

Catalyst Electrodes with PtCu Nanowire Arrays In Situ Grown on Gas Diffusion Layers for Direct Formic Acid Fuel Cells.

The excellent performance and safety of direct formic acid fuel cells (DFAFCs) promote them as potential power sources for portable electronic devices. However, their real application is still highly challenging due to the poor power performance and high complexity in the fabrication of catalyst electrodes. In this work, we demonstrate a new gas diffusion electrode (GDE) with ultrathin PtCu alloy nanowire (NW) arrays in situ grown on the carbon paper gas diffusion layer surface. The growing process is achieved by a facile template- and surfactant-free self-growth assisted reduction method at room temperature. A finely controlled ion reduction process tunes the nucleation and crystal growth of Pt and Cu leading to the formation of alloy nanowires with an average diameter of about 4 nm. The GDE is directly used as the anode for DFAFCs. The results in the half-cell GDE measurement indicate that the introduction of Cu in PtCu NWs boosts the direct oxidation pathway for formic acid. The Pt3Cu1 NW GDE shows a 2.4-fold higher power density compared to the Pt NW GDE in the membrane electrode assembly test in single cells.

Ultrahigh Pt‐Mass‐Activity Hydrogen Evolution Catalyst Electrodeposited from Bulk Pt

AbstractMaximizing the Pt utilization is important for the widescale implementation of Pt‐based hydrogen evolution reaction (HER) electrocatalysts, owing to the scarcity of Pt. Here, three‐component heterostructured HER catalysts with ultrahigh Pt mass activity in which hollow PtCu alloy nanospheres are supported on an array of WO3 on Cu foam, are reported. It has been pointed out that the use of Pt counter electrode in a three‐electrode configuration in evaluating catalysts’ HER performances in acidic media carries the risk of contaminating the working electrode in previous reports. Here, the authors rationally utilize this “contaminating” to “activate” low‐HER‐activity materials, maximizing the Pt utilization. As a result, ultrahigh Pt mass activity is achieved, that is 1.35 and 10.86 A mg−1Pt at overpotentials of 20 and 100 mV, respectively, 27 and 13 times higher than those of commercial Pt/C catalysts, outperforming some state‐of‐the‐art Pt‐single‐atom catalysts. The hollow sphere structure and PtCu alloying increase the number and reactivity of active sites. Density function calculations and electrochemical experiments reveal that the synergy between WO3 and Pt is also responsible for the high HER activity where the hydrogen spillover effect triggers the Volmer–Heyrovsky mechanism and promotes the rapid removal of H* from Pt to re‐expose the active sites.

Platinum−Copper Bimetallic Nanoparticles Supported on TiO2 as Catalysts for Photo−thermal Catalytic Toluene Combustion

Oxidation of toluene into CO2 and H2O under mild conditions via a photo-promoted catalytic process has been regarded as a promising tactic to solve the toluene pollution issues in air. In this work, we examined the performance of Pt–Cu/TiO2 nanocatalysts with tunable mass ratios between Pt and Cu elements for photocatalytic, thermocatalytic, and photo–thermal catalytic degradation of toluene. In the photo–thermal catalytic process, 80% of the inlet toluene could be decomposed over Pt0.4 wt %Cu0.1 wt %–TiO2 catalyst at 77 °C under light irradiation, while 100 °C was needed for Pt0.5 wt %–TiO2 to achieve the same catalytic efficiency. The greatly enhanced activity could be ascribed to the synergistic effects arising from photothermal effects of the high dispersion of PtCu alloy nanoparticles, intimate interaction between the metal elements, and the photoexcitation of TiO2. In the photocatalytic process, the highest photocatalytic toluene conversion rate was obtained on the PT-4 catalyst (55%) and there was a negligible conversion rate (0.38%) of toluene under thermocatalytic conditions at 110 °C, delineating that the efficiency of photo–thermal catalytic degradation of toluene was much higher than that of a thermocatalytic or a photocatalytic process, illustrating the synergistic effects between light irradiation and heat. This work highlights the high photo–thermal catalytic toluene degradation performance of PtCu alloy nanoparticles and the synergistic effects of light irradiation and heat.

PtCu alloy cocatalysts for efficient photocatalytic CO2 reduction into CH4 with 100% selectivity

In this paper, PtCu alloys with varying Pt/Cu ratios were deposited onto TiO2 nanocrystals to selectively photoreduce CO2 into CH4.

Engineering PtCu nanoparticles for a highly efficient methanol electro-oxidation reaction.

Achieving a highly efficient and durable methanol electro-oxidation catalyst in acid media is critical for the practical utilization of direct methanol fuel cells (DMFCs) at the commercial scale. Herein, we report a facile and effective one-pot strategy for the synthesis of carbon-supported PtCu alloy nanoparticles (PtCu NPs) with a Pt-rich surface, small particle size and uniform dispersion. The as-prepared PtCu NPs with the optimal alloy composition (Pt2Cu) exhibit a significantly improved electrochemical methanol oxidation reaction performance in terms of a high activity, superior CO tolerance and remarkable durability, in contrast to those of commercial Pt/C catalysts in acid media. Particularly, the Pt2Cu/C catalyst exerts a 4.5 times enhancement in the mass activity and a larger If/Ib value compared to those of commercial Pt/C (Pt/Ccomm). The enhanced catalytic activities can be ascribed to the high utilization of Pt and the high index facets of the surface. Also, the addition of Cu downshifts the d-band center of Pt and improves the CO tolerance during the methanol oxidation reaction process. This work provides an efficient strategy for designing desired Pt-based alloys for various catalytic reactions.