Performance For Formic Acid Electrooxidation Research Articles

Boosting electrocatalytic oxidation of formic acid on SnO2-decorated Pd nanosheets

Formic acid (HCOOH), as a natural biomass, is a promising feedstock for low temperature fuel cells, and rational development of efficient catalysts for electrochemical dehydrogenation of HCOOH plays a key role toward its full chemical energy utilization. Herein, Pd nanosheets decorated with SnO2 nanoflakes (denoted hereafter as Pd@SnO2-NSs) are designed as a composite catalyst, showing superior performance for formic acid electro-oxidation, as compared to pristine Pd nanosheets (Pd-NSs). In situ attenuated total reflection infrared (ATR-IR) spectroscopic results suggest a promoted formate pathway on the Pd@SnO2-NSs with a suppressed accumulation of CO poisoning species. DFT calculations further indicate that the Pd (111) surface modified with SnO2 has lower energy barriers for the bidentate formate formation, the bidentate to monodentate formate transformation and the C-H bond scission.

PVF-PPy Composite as Support Material for Facile Synthesis of Pt@PVF-PPy Catalyst and Its Electrocatalytic Activity Towards Formic Acid Oxidation

Preparation and characterization of a Pt-based catalyst supported on poly(vinylferrocenium)-poly(pyyrole) conducting polymer composite (Pt@PVF-PPy) was described for electrocatalytic oxidation of formic acid. Pt precursor was aqueous solution of K2PtCl4 and electrochemical and chemical reduction methods were compared for optimum catalyst performance. Other experimental parameters such as polymer film thickness and Pt loading were also optimized with respect to the formic acid oxidation peak current values. Scanning electron microscopy, cyclic voltammetry and chronoamperometry methods were used for physical and electrochemical characterization of the catalyst system. When compared with similar Pt-based conducting polymer supported catalyst systems, the Pt@PVF-PPy catalyst revealed superior performance for formic acid electrooxidation.

Silsesquioxane stabilized platinum-palladium alloy nanoparticles with morphology evolution and enhanced electrocatalytic oxidation of formic acid

Bimetallic catalysts have attracted enormous attention with their enhanced electrocatalytic properties in fuel cells. Herein a series of silsesquioxane (POSS) stabilized platinum-palladium (PtPd) alloy nanoparticles (NPs) with morphology evolution were facilely synthesized with the co-chemical reduction using formaldehyde as the reductant. By varying the ratio of Pt to Pd, the PtPd alloy NPs evolved from truncated octahedrons to octahedrons, and triangular nanoplates. The mechanism of morphology evolution is that Pt and Pd could self-assemble on POSS to form PtxPd1−x intermediates with different Pt/Pd ratios. In addition, formaldehyde could selectively bind to the {1 1 1} facets of Pd to control the growth rates of different facets and help PtxPd1−x intermediates with different Pt/Pd ratio grow into different morphology of PtxPd1−x alloys. The morphology tuning endowed the PtPd alloy NPs superior performance for formic acid electrooxidation. Compared with Pt, Pd NPs, and commercial Pt/C catalyst, the PtPd alloy NPs displayed larger electrochemically active surface area, enhanced electrocatalytic activity and durability toward oxidation of formic acid, and increased CO tolerance. This work suggested that modification of catalytic activity through morphology tuning with composition adjustment might provide some new pathways for the design of promising catalysts with advanced performance.

Kinetic Study of Formic Acid Electrochemical Oxidation on Supported Pd Based Electrocatalysts

Developing high performance catalyst based on Pd/C catalyst is critical in investigating and commercializing direct formic acid fuel cell. The improvement of the electron-transfer rate of novel catalysts could solve the sluggish reaction kinetics of formic acid electro-oxidation reaction in some extent. We have demonstrated that phosphotungstic acid (PWA) modified Pd/C catalyst could improve the electro-oxidation activity toward formic acid. In this paper, the electrochemical oxidation reaction kinetics of PWA modified Pd/C catalyst were studied by cyclic voltammetry (CV), Tafel polarization, electrochemical impedance spectroscopy (EIS) and rotating disc voltammetry (RDV) at different scanning rates and temperatures. The results showed that smaller apparent activation energy, charge transfer resistance and Tafel slope of formic acid electro-oxidation from Pd/PWA–C electrode catalyst was obtained, which indicated better electrocatalytic kinetics by PWA modification. The rate-determining step of formic acid electro-oxidation is diffusion process and reaction paths are different with potential. The larger diffusion coefficients of Pd/PWA–C electrode catalyst was verified by CV, EIS and RDV, respectively. With the help of electrochemical measurements, it is concluded that PWA modified Pd/C catalyst has better electrocatalytic activity and faster kinetic performance for formic acid electro-oxidation.

Light-induced deposition of Pd-based nanoalloy on TiO 2 nanotubes for formic acid electrooxidation

In this paper, we reported a facile UV-light induced method for depositing the Pd nanoparticles and Pd–Pt nanoalloys onto vertically oriented TiO2 nanotube (TNT) arrays with anodization. As-prepared TNT-supported Pd nanoparticles and Pd–Pt nanoalloys were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). EDS and XRD analysis verified that Pd and Pt particles had been successfully reduced. SEM images showed that Pd and Pd–Pt elements were evenly distributed on the surface of the TiO2 nanotube, and XPS measurement suggested electronic effects of the alloying elements on TiO2 nanotube. The electrocatalytic activities of TNTs-supported Pd-based catalysts had been investigated by the conjunction of cyclic voltammetry, linear sweeping voltammetry, chronoamperometry and CO stripping voltammograms. The results indicated that Pd0.97Pt0.03/TNTs catalysts exhibited the best electrocatalytic performance for formic acid electrooxidation, making it very attractive for practical applications in direct formic acid fuel cells.

Controlled Growth of Pt–Au Alloy Nanowires and Their Performance for Formic Acid Electrooxidation

Pt–Au alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current and were used as the electrocatalyst for formic acid oxidation. The frequency and voltage of the alternating current and the electrolyte composition were adjusted to precisely control the morphologies, alloying structures and composition. The characteristics of Pt–Au alloy nanowires were analyzed by scanning electron microscopy, X-ray diffraction and transmission electron spectroscopy. Electrocatalytic performance of formic acid oxidation at Pt–Au alloy nanowires electrode was investigated by cyclic voltammetry and chronoamperometry. The results showed that the Pt–Au alloy nanowires possessed highly-crystalline morphologies, the controllable bimetallic composition and single-phase alloy structures, which mainly grow in the crystal orientation. The electrocatalytic activity of formic acid oxidation strongly depended on the bimetallic Pt/Au composition. The Pt35Au65 alloy nanowires displayed superior electrocatalytic performance and high stability toward the electrooxidation of formic acid in acidic solution, owing to the ensemble effect of the Pt and Au components. These findings provided insights into the design of the Pt–Au bimetallic nanomaterials as electrocatalysts for formic acid oxidation.

PtFe/nitrogen-doped graphene for high-performance electrooxidation of formic acid with composition sensitive electrocatalytic activity

A PtFe/N-doped graphene electrocatalyst with a reduced amount of Pt is developed, which shows a good catalytic performance for formic acid electrooxidation due to the synergistic effects between the NG substrate and PtFe nanoalloy.

High stability and high activity Pd/ITO-CNTs electrocatalyst for direct formic acid fuel cell

Indium tin oxide (ITO) and carbon nanotube hybrid has been explored as a support for Pd catalyst. Pd/ITO-CNTs catalysts with different ITO contents were prepared by the microwave-assisted polyol process. The as-prepared Pd/ITO-CNTs catalysts were characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and electrochemical measurements in this work. The TEM results show that Pd particle size distribution in the Pd/ITO-CNTs catalyst is more uniform than that in Pd/CNTs, indicating that the ITO can promote the dispersion of Pd nanoparticles. It is found that there is metal-support interaction between Pd nanoparticles and ITO in the Pd/ITO-CNTs catalyst through XPS test. The results of electrochemical tests prove that the Pd/ITO-CNTs catalysts exhibit higher electro-catalytic activity and stability than Pd/CNTs toward formic acid electrooxidation. When the ITO content is 50% of ITO-CNTs support mass, the Pd/ITO-CNTs catalyst has the best catalytic performance for formic acid electrooxidation. The peak current density of formic acid electrooxidation on the Pd/ITO-CNTs50% electrode is 1.53 times as high as that on Pd/CNTs, 2.31 times higher than that on Pd/ITO. The results of aging test show that the peak current density on the Pd/ITO-CNTs decreases by only 14.0%, while 56.1% on the Pd/CNTs after 500 cycles. It is due to the promoting effect of In2O3 and SnO2 in ITO, and metal-support interaction between Pd nanoparticles and ITO.

Rapid fabrication of Cu/Pd nano/micro-particles porous-structured catalyst using hydrogen bubbles dynamic template and their enhanced catalytic performance for formic acid electrooxidation

In this work, a self-supporting Pd–Cu bimetallic film with 3D porous structure was electrodeposited at the surface of glassy carbon electrode (GCE) using a facile double-template fabrication process, including hydrogen bubble templating method and galvanic replacement reaction, and its performance investigated as a catalyst for formic acid oxidation (FAO). The structure of the Cu/Pd porous film was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The electrocatalytic activity of the as-prepared catalysts with high surface areas were evaluated in sulfuric acid solution containing 1 M formic acid using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The Cu/Pd porous structure exhibited significantly high current densities of formic acid oxidation compared to the Cu/Pd particles film catalyst. The effects of galvanic replacement time and concentration of formic acid on the catalytic activity of as-prepared electrode for FAO were comparatively investigated.

An efficient antimony doped tin oxide and carbon nanotubes hybrid support of Pd catalyst for formic acid electrooxidation

We report on a mixture of antimony doped tin oxide (ATO) and carbon nanotubes as a novel support of Pd catalyst (Pd/ATO-CNTs) with the aims to enhance electron and proton conductivity of hybrid support, and catalytic activity and stability for formic acid electrooxidation. The surface content, morphology and structure of the as-prepared Pd/ATO-CNTs catalysts with different CNTs contents have been characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), inductively coupled plasma-optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and high angle annular dark field STEM (HAADF-STEM), respectively. The electrocatalytic properties of the samples for formic acid electrooxidation reaction are investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that the activity and stability of Pd/ATO-CNTs catalyst is obviously higher than that of Pd/CNTs catalyst for formic acid electrooxidation due to unique physical and chemical properties of ATO and metal-support interaction between Pd nanoparticles and ATO. Moreover, the Pd/ATO-CNTs10 (CNTs content is 10 wt.% of ATO-CNTs support mass) with smaller Pd particle size and narrower size distribution on surface of the hybrid support exhibits the best performance for formic acid electrooxidation among all the samples.

Preparation of PdAu/C-Sb2O5·SnO2 electrocatalysts by borohydride reduction process for direct formic acid fuel cell

Pd/C-Sb2O5·SnO2 and PdAu/C-Sb2O5·SnO2 electrocatalysts with different PdAu atomic ratio (90:10, 70:30, and 50:50) were prepared by borohydride reduction method, and characterized by X-ray diffraction, transmission electron microscopy, cyclic voltammetry, chronoamperommetry, and performance test on direct formic acid fuel cell at 100 °C. X-ray diffraction showed for Pd/C-Sb2O5·SnO2 the presence of Pd face-centered cubic (fcc) system, while for PdAu/C-Sb2O5·SnO2 it showed the presence of Pd fcc phase, PdAu fcc alloys and a segregated phases fcc Pd-rich and Au-rich phases. TEM micrographs and histograms for all electrocatalysts showed that the nanoparticles where not well dispersed on the support and some agglomerates were present. The electrochemical studies showed that PdAu/C-Sb2O5·SnO2 (70:30) had superior performance for formic acid electro-oxidation at 25 °C compared to others electrocatalysts prepared while PdAu/C-Sb2O5·SnO2 (90:10) showed superior performance in direct formic acidic fuel cell at 100 °C. These results indicated that the addition of 10–30 % Au to Pd favor the electro-oxidation of formic acid. This effect could be attributed to the synergy between the constituents of the electrocatalyst (metallic Pd and Au, SnO2, and Sb2O5·SnO2).

Synthesis and characterization of Pd catalysts supported on carbon microspheres for formic acid oxidation

A facile preparation of Pd catalyst using carbon microspheres as support was introduced in this paper. The carbon microspheres were prepared with a simple method from dextrose via hydrothermal process and used as catalysts support for formic acid electrooxidation. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses revealed that the as-prepared face-centered cubic crystal Pd nanoparticles were well-dispersed on the surface of the carbon microspheres, and the mean diameter of the nanoparticles was 8.8 nm. The effect of the support on the catalyst performance for formic acid electrooxidation was studied. The as-prepared catalyst showed the enhanced electrochemical surface active area and the higher electrocatalytic activity towards formic acid oxidation compared with Pd/CNTs and Pd/XC-72 catalysts prepared at room temperature. Electrochemical analysis suggested that the carbon microspheres might be good candidates to be used as the supports of catalyst for formic acid electrochemical oxidation.

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

Highly dispersed and ultrafine palladium–phosphorus (Pd–P) nanoparticles (NPs) are prepared with a novel phosphorus reduction method. The structural and electronic properties of Pd–P NPs are characterized using Fourier transform infrared (FT-IR), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrooxidation of formic acid on Pd–P NPs are investigated by using cyclic voltammetry, chronoamperometry and CO-stripping measurements. The physical characterizations indicate the doped P element can enhance the content of Pd 0 species in Pd NPs, decrease the particle size and improve the dispersion of Pd–P NPs. The electrochemical measurements show the Pd–P NPs have a better catalytic performance for formic acid electrooxidation than Pd NPs.

Synthesis of carbon supported palladium nanoparticles catalyst using a facile homogeneous precipitation-reduction reaction method for formic acid electrooxidation

A highly dispersed and ultrafine carbon supported Pd nanoparticles (Pd/C) catalyst is synthesized by a facile homogeneous precipitation-reduction reaction method. Under the appropriate pH conditions, [PdCl 4] 2− species in PdCl 2 solution are slowly transformed into the insoluble palladium oxide hydrate (PdO·H 2O) precipitation by heat treatment due to a slow hydrolysis reaction, which results in the generation of carbon supported PdO·H 2O nanoparticles (PdO·H 2O/C) sample with the high dispersion and small particle size. Consequently, a highly dispersed and ultrafine Pd/C catalyst can be synthesized by PdO·H 2O → Pd 0 in situ reduction reaction path in the presence of NaBH 4. As a result, the resulting Pd/C catalyst possesses a significantly electrocatalytic performance for formic acid electrooxidation, which is attributed to the uniformly sized and highly dispersed nanostructure.

Highly dispersed carbon-supported Pd nanoparticles catalyst synthesized by novel precipitation–reduction method for formic acid electrooxidation

The highly dispersed and ultrafine carbon-supported Pd nanoparticles (Pd/C) catalyst is synthesized by using an improved precipitation–reduction method, which involves in Pd II → PdO·H 2O → Pd 0 reaction path. In the method, palladium oxide hydrate (PdO·H 2O) nanoparticles (NPs) with high dispersion is obtained easily by adjusting solution pH in the presence of 1,4-butylenediphosphonic acid (H 2O 3P-(CH 2) 4-PO 3H 2, BDPA). After NaBH 4 reduction, the resulting Pd/C catalyst possesses high dispersion and small particle size. As a result, the electrochemical measurements indicate that the resulting Pd/C catalyst exhibits significantly high electrochemical active surface area and high electrocatalytic performance for formic acid electrooxidation compared with that prepared by general NaBH 4 reduction method.