Electrocatalysts For Ethanol Oxidation Research Articles

High-selective and effective carbon nanotubes supported ultrasmall PtPdRh electrocatalysts for ethanol oxidation

Pt as the most effective ethanol oxidation reaction (EOR) catalyst confronts the problems of insufficient activity, unsatisfactory selectivity and poisoning by intermediates. It hindered the practical use of direct ethanol fuel cells (DEFCs). Therefore, in this work, carbon nanotubes (CNTs) supported ultrasmall PtPdRh nanoparticles (PtPdRh/CNTs, ∼2.3 nm) were synthesized with polyallylamine hydrochloride and hexadecyl trimethyl ammonium bromide for EOR. Pd as the core may reduce the cost, and Rh is helpful to cleave C−C bond. The introduction of Pd and Rh further brings about synergetic effect and adjustment of electronic structures. Moreover, partially oxidized PtPdRh nanoparticles is favorable to generate *OH species in alkaline media to accelerate intermediates removal. Benefit from the nanostructures, the mass and specific activities of PtPdRh/CNTs (1345.16 mA·mg−1 and 1.37 mA·cm−2) are higher than both commercial Pt/C and corresponding mono-/bi-metal catalysts. PtPdRh/CNTs also exhibit excellent selectivity and anti-poisoning ability, with jf/jb as high as 6.17, larger than most up-to-date reports. Besides, PtPdRh/CNTs own excellent stability and durability. This study adopting a rational design strategy to fabricate high-selective and effective EOR catalysts is conducive to the practical application of DEFCs.

Electro-Design of Bimetallic PdTe Electrocatalyst for Ethanol Oxidation: Combined Experimental Approach and Ab Initio Density Functional Theory (DFT)-Based Study.

An alternative electrosynthesis of PdTe, using the electrochemical atomic layer deposition (E-ALD) method, is reported. The cyclic voltammetry technique was used to analyze Au substrate in copper (Cu2+), and a tellurous (Te4+) solution was used to identify UPDs and set the E-ALD cycle program. Results obtained using atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques reveal the nanometer-sized flat morphology of the systems, indicating the epitaxial characteristics of Pd and PdTe nanofilms. The effect of the Pd:Te ratio on the crystalline structure, electronic properties, and magnetic properties was investigated using a combination of density functional theory (DFT) and X-ray diffraction techniques. Te-containing electrocatalysts showed improved peak current response and negative onset potential toward ethanol oxidation (5 mA; −0.49 V) than Pd (2.0 mA; −0.3 V). Moreover, DFT ab initio calculation results obtained when the effect of Te content on oxygen adsorption was studied revealed that the d-band center shifted relative to the Fermi level: −1.83 eV, −1.98 eV, and −2.14 eV for Pd, Pd3Te, and Pd3Te2, respectively. The results signify the weakening of the CO-like species and the improvement in the PdTe catalytic activity. Thus, the electronic and geometric effects are the descriptors of Pd3Te2 activity. The results suggest that Pd2Te2 is a potential candidate electrocatalyst that can be used for the fabrication of ethanol fuel cells.

Interfacial engineering Pb skin-layer at Rh surface to promote ethanol electrooxidation into CO2 in alkaline media

Rh is recently regarded as the promising electrocatalyst for ethanol oxidation into CO2 due to its high activity of splitting C–C bond, whereas the further oxidation of as-generated C1 species (CO and CHx) is pretty sluggish at Rh surface. To solve this, here the oxophile Pb skin-layer is inhabited at Rh nanoparticles to obtain the Pb@Rh core-shell structure with controllable Pb coverage (θPb), expecting to tune the surface reactivity of ethanol oxidation reaction (EOR) according to the Langmuir-Hinshelwood Mechanism as well as the strain effect. Fortunately, the as-obtained Pb@Rh/C catalysts indeed significantly enhance the catalysis performance of EOR, the optimal mass activity is ca. 1450 mA mg-1 metal when θPb is ca. 0.53 (Pb0.53@Rh), being ca. 13 times higher than pristine Rh catalyst. Meanwhile, as much as ca. 57% of the initial EOR current remains even after a 20,000-s durability measurement. And the apparent C1 pathway faraday efficiency (CO2 selectivity) is also estimated to be ca. 21% at Pb0.53@Rh surface. This work can provide a simple and promising protocol to tune the surface reactivity by interfacial engineering manipulation.

Enhancing Ethanol Electrooxidation Stability over PtIr/GN Catalysts by In Situ Formation of IrO2 at Adjacent Sites

PtIr alloy is considered as one of the most promising catalysts for ethanol electrooxidation due to its excellent C–C bond breaking and dehydrogenation abilities. However, a small amount of intermediate species produced by ethanol oxidation can still poison Pt, thereby affecting the stability of ethanol oxidation. Here, graphene supported PtIr nanoparticles (PtIr/GN) with a Pt: Ir atomic ratio of 3:1 is synthesized by a simple hydrothermal reduction and thermal annealing. The physicochemical analyses show that IrO2 is formed in situ in PtIr/GNs (O) during annealing and located adjacent to PtIr alloys. IrO2 and PtIr are evenly dispersed on GNs. The electrochemical results indicate that PtIr/GNs (O) has higher catalytic activity and stability for ethanol electrooxidation than PtIr/GNs. After 1000 voltammetric cycles, the peak current density for PtIr/GNs (O) is 2.5 times higher than that for PtIr/GNs. The outstanding electrochemical performance of PtIr/GNs (O) is derived from PtIr alloy that promotes the cleavage of the C–C bond and weakens the adsorption of Pt to intermediate species, IrO2 that improves the tolerance of Pt to CO-like species and enhances the structural stability of Pt, and PtIr alloy and IrO2 in adjacent positions that synergistically improve the stability of catalytic ethanol oxidation.

Nanosized Pd-loaded the Fe3C encapsulated by N-doped carbon nanotube as an electrocatalyst for oxygen reduction and ethanol oxidation reactions

Iron carbide-encapsulated nitrogen-doped carbon nanotubes (Fe3C@NCNTs) and Pd that is loaded onto Fe3C@NCNTs (Pd/Fe3C@NCNTs) electrocatalysts were synthesized. The valence state of Pd that was loaded onto the Pd/Fe3C@NCNTs surface is in the Pd0 and Pd2+ forms and Pd0 is the main form. The electrochemical measurement results imply that the Fe3C@NCNT catalyst exhibits an electrocatalytic property in the oxygen reduction reaction (ORR). The Pd/Fe3C@NCNT electrocatalyst has a good catalytic property toward ORR and ethanol oxidation reaction (EOR) in an alkaline solution. The half-wave potential (E1/2) on the Pd/Fe3C@NCNT electrocatalyst toward the ORR can reach 0.904 V, which is higher than that on commercial 20 wt% Pt/C (0.856 V). The forward oxidation peak current density (jf) on the Pd/Fe3C@NCNT electrocatalyst for ethanol oxidation is 1.655 A mg−1, which is larger than that on commercial 10 wt% Pd/C (0.430 A mg−1). The excellent electrocatalytic property of the Pd/Fe3C@NCNT electrocatalyst is contributed to the many active sites and synergistic effects between Pd and Fe3C@NCNTs. The density functional theory (DFT) calculation result implies that the electron mobility increases in the recombination area for Pd and Fe3C@NCNTs.

Copper-doped nickel oxyhydroxide for efficient electrocatalytic ethanol oxidation

Rational design of low-cost and efficient electrocatalysts for ethanol oxidation reaction (EOR) is imperative for electrocatalytic ethanol fuel cells. In this work, we developed a copper-doped nickel oxyhydroxide (Cu-doped NiOOH) catalyst via in situ electrochemical reconstruction of a NiCu alloy. The introduction of Cu dopants increases the specific surface area and more defect sites, as well as forms high-valence Ni sites. The Cu-doped NiOOH electrocatalyst exhibited an excellent EOR performance with a peak current density of 227 mA·cm−2 at 1.72 V versus reversible hydrogen electrode, high Faradic efficiencies for acetate production (> 98%), and excellent electrochemical stability. Our work suggests an attractive route of designing non-noble metal based electrocatalysts for ethanol oxidation.

Self-Assembled Pt/MoCx/MWCNTs Nano Catalyst for Ethanol Electrooxidation of Fuel Cells.

Direct ethanol fuel cells (DEFCs) have attracted more and more attention because of their unique advantages such as low cost and low toxicity. However, sluggish C-C bond cleavage during the ethanol electrooxidation reaction (EOR) in acidic media results in a lower energy yield and gravely hinders the commercialization of DEFCs. Therefore, it is very necessary to develop an anode catalyst with high performance, high stability and low cost to solve this problem. In this paper, Pt/MoCx/MWCNTs nanocomposites with different mass ratios of PtMo were obtained through a molecular self-assembly technology. The structure and morphology of Pt/MoCx/MWCNTs nanocomposites were characterized by several techniques such as XRD, FESEM, XPS, etc. The electrochemical performance and stability of Pt/WCx/MWCNTs electrocatalysts toward EOR were investigated in acid electrolytes. The results show that PtMo exists in the form of alloy. The size of Pt/MoCx nanoparticles is very uniform with an average size of ∼24 nm. The Pt/MoC0.25/MWCNTs exhibits excellent electrocatalytic activities with an electrochemically active surface area of 37.1 m2 g−1, a peak current density of 610.4 mA mgPt −1 and a steady-state current density of 39.8 mA mgPt −1 after 7,200 s, suggesting that the Pt/MoC0.25/MWCNTs is a very promising candidate for application in EOR of DEFCs.

Designing New Material Based on Functionalized Multi-Walled Carbon Nanotubes and Cu(OH)2-Cu2O/Polypyrrole Catalyst for Ethanol Oxidation in Alkaline Medium.

In this work, copper(II) hydroxide (Cu(OH)2) and copper oxide (Cu2O) nanostructures are deposited on functionalized multi-walled carbon nanotubes/polypyrrole to report an efficient electrocatalyst for ethanol oxidation in alkaline medium. In the first step, the deposition of functionalized multi-walled nanotubes of carbon (F-MWCNTs) on the electrode surface was carried out using drop casting mode followed by the electrodeposition of polypyrrole (PPy) and copper nanoparticles (Cu-Nps) using galvanostatic mode. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed in order to study the morphology and the structure of the elaborated catalysts. Electrochemical characterization conducted by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed that the introduction of functionalized multi-walled carbon nanotubes enhances the electric properties of the nanocomposites and offers a large active surface area. The prepared electrocatalyst was then tested in a solution of 0.1 M NaOH containing 0.2 M of ethanol showing high performance (7 mA cm−2 at 0.85 V vs Ag/AgCl) and good stability (over 1800 s) toward ethanol oxidation.

Surface Nitridation of PdCu Nanosheets to Promote Charge Transfer and Suppress CO Poisoning toward Ethanol Electrooxidation

AbstractAlthough PdCu alloy is recognized as an active catalyst for ethanol electrooxidation, its activity needs significant enhancement to satisfy the practical application. In this study, surface nitrided PdCu nanosheets are constructed through a facile nitrogen plasma treatment. The obtained catalyst shows highly enhanced catalytic activity and stability toward ethanol oxidation reaction in comparison with normal PdCu nanosheets and Pd nanosheets. The improvement should be ascribed to the combined electronic and structural effects from introduced Cu and facile surface nitridation, which promote charge transfer and suppress CO poisoning. This work offers a guideline to design and synthesize efficient catalysts for energy electrocatalysis by rational surface engineering.

Combining surface chemical functionalization with introducing reactive oxygen species boosts ethanol electrooxidation.

The introduction of functional groups or oxygen vacancies into Pd-based electrocatalysts is a powerful strategy for enhancing the electrocatalytic performances for many electrocatalytic reactions. Herein, an amorphous ceria-modified Pd nanocomposite anchored on D-4-amino-phenylalanine (DAP)-functionalized graphene nanosheets (Pd-CeO2-x/FGS) was prepared by a facile and effective one-pot synthetic strategy and further used as an electrocatalyst for the ethanol oxidation reaction (EOR) in alkaline electrolytes. The obtained Pd-CeO2-x/FGS exhibits relatively high electrocatalytic activity, fast kinetics and excellent antipoisoning ability as well as robust durability for EOR, outperforming the comparable electrocatalysts as well as commercial Pd/C. The experimental results show that the enhanced EOR properties of Pd-CeO2-x/FGS can be attributed to the DAP-functionalization and CeO2-x-modification. Adequate functional groups (amino and carboxyl groups) and abundant oxygen vacancies were introduced in Pd-CeO2-x/FGS by DAP-functionalization and CeO2-x-modification. The functional groups facilitate the anchoring of small nanoparticles onto the substrate as well as modulate the electron density of Pd. The oxygen vacancies boost the adsorption ability of the reactive oxygen species (OHads) and accelerate the kinetics of the potential-limiting step for EOR. This study proposes a new strategy for the rational design of highly efficient catalysts for the electro-oxidation reaction.

Palladium Nanoparticles Anchored on Mxene-Based N-Doped Porous Carbon Nanosheets as an Advanced Electrocatalyst for Ethanol Oxidation

Palladium Nanoparticles Anchored on Mxene-Based N-Doped Porous Carbon Nanosheets as an Advanced Electrocatalyst for Ethanol Oxidation

Amorphous palladium-based alloy nanoparticles as highly active electrocatalysts for ethanol oxidation.

Amorphous Pd-P metal-metalloid alloy nanoparticles showed a higher electrochemical ethanol oxidation reaction performance than crystalline Pd nanoparticles. The high performance was attributed to the rich defective coordination unsaturated sites and the P alloying, which enhanced the OH adsorption.

High-Selective and Effective Carbon Nanotubes Supported Ultrasmall Ptpdrh Electrocatalysts for Ethanol Oxidation

High-Selective and Effective Carbon Nanotubes Supported Ultrasmall Ptpdrh Electrocatalysts for Ethanol Oxidation

Nickel chalcogenides as selective ethanol oxidation electro-catalysts and their structure-performance relationships.

Five nickel chalcogenides have been studied and they showed high selectivity towards selective ethanol electro-oxidation to acetic acid. The activities of the different nickel chalcogenides are correlated with the Ni-Ni projected distances of the catalysts.

Ultrasmall AuPd nanoclusters on amine-functionalized carbon blacks as high-performance bi-functional catalysts for ethanol electrooxidation and formic acid dehydrogenation

The synthesis of ultrasmall metal nanoclusters (NCs) with high catalytic activities is of great importance for the development of clean and renewable energy technologies but remains a challenge. Here we report a facile wet-chemical method to prepare ∼1.0 nm AuPd NCs supported on amine-functionalized carbon blacks. The AuPd NCs exhibit a specific activity of 5.98 mA cmAuPd−2 and mass activity of 5.25 A mgAuPd−1 for ethanol electrooxidation, which are far better than those of commercial Pd/C catalysts (1.74 mA cmPd−2 and 0.54 A mgPd−1). For formic acid dehydrogenation, the AuPd NCs have an initial turn over frequency of 49339 h−1 at 298 K without any additive, which is much higher than those obtained for most of reported AuPd catalysts. The reported synthesis may represent a facile and low-cost approach to prepare other ultrasmall metal NCs with high catalytic activities for various applications.

Pd decorated Co–Ni nanowires as a highly efficient catalyst for direct ethanol fuel cells

The storage and conversion of energy necessitates the use of appropriate electrochemical systems and chemical reaction catalysts. This work presents newly developed catalysts for electrooxidation of ethanol in an alkaline medium. Nanocatalysts composed of Co–Ni nanowires (Co–Ni NWs) decorated with Pd nanoparticles (Pd NPs) were made at varying metal ratios and their chemical composition and structure was investigated in detail. The synthesis involved a wet chemical reduction assisted by a magnetic field, which led to the generation of NWs, followed by the deposition of spherical Pd NPs on their surface. The best catalytic activity was obtained for the catalyst made of Co3–Ni7 decorated with Pd NPs, which exhibited EOR of 8003 mA/mgPd for only 0.86 wt% of Pd loading. The results can be explained by the synergistic effect between the morphology of the bimetallic support and the favorable interaction of oxophilic Co, Ni with catalytic Pd.

Pd electrodeposition on a novel substrate of reduced graphene oxide/ poly(melem-formaldehyde) nanocomposite as an active and stable catalyst for ethanol electrooxidation in alkaline media

Palladium nanoparticles (Pd NPs) were successfully electrodeposited on a reduced graphene oxide/poly(melem-formaldehyde) nanocomposite (rGO/PMF) NC as a catalyst for ethanol electrooxidation in alkaline media; melem was used as a nitrogen-rich source in the substrate structure for the first time. The specific surface area and average pore diameter of (rGO/PMF) NC were 481.61 m2 gr−1 and 10.23 nm, respectively. High nitrogen doping and structural defects improved the dispersion and anchoring of Pd NPs on (rGO/PMF) NC. The onset potential (Eonset) of Pd/(rGO/PMF) NC was shifted negatively to 110 mV, in comparison to Pd/rGO. Also, the current density and electrochemical active surface area (EASA) of Pd/(rGO/PMF) NC were enhanced to 44 mA cm−2 and 67.58 m2 gr−1, respectively, as compared to Pd/rGO. Furthermore, the stability of Pd/(rGO/PMF)NC was indicated against ethanol oxidation intermediates during 7000 s. This work also produced a superior graphene-based material for direct ethanol fuel cell anode catalysts applications.

High-index faceted Pt-Ru alloy concave nanocubes with enhancing ethanol and CO electro-oxidation

High-index faceted Pt-based alloys are the promising electrocatalysts for ethanol oxidation due to their high-index facets (HIFs) structure, alloying electronic effect, and bi-functional mechanism. However, the controllable synthesis of Pt-based alloys enclosed by HIFs remains a challenge as the high surface energy, distinct standard reduction potential and atom sizes between different metals. In the present work, we propose a shape- and composition-controlled synthesis of Pt-Ru alloy concave nanocubes with high-index {510} facets via combining deep eutectic solvent (DES) with electrochemical square-wave potential. Compared with the monometallic Pt concave nanocubes and quasi-spherical Pt-Ru alloys, the as-synthesized concave cubic Pt-Ru alloys exhibit an excellent electro-oxidation performance of ethanol and CO due to the high density of low-coordinated Pt step sites (HIFs structure) and the unique electronic effect of Pt-Ru (alloying structure). Density functional theory (DFT) calculations reveal that OH* formation from water dissociation on Pt-Ru surface is apparently the rate determining step. The present of Ru on Pt(510) surface is capable to promote the OH* adsorption and then enhance the ethanol electro-oxidation reactivity and CO-resistance ability.

Construction of Pd-Zn dual sites to enhance the performance for ethanol electro-oxidation reaction

Rational design and synthesis of superior electrocatalysts for ethanol oxidation is crucial to practical applications of direct ethanol fuel cells. Here, we report that the construction of Pd-Zn dual sites with well exposure and uniformity can significantly improve the efficiency of ethanol electro-oxidation. Through synthetic method control, Pd-Zn dual sites on intermetallic PdZn nanoparticles, Pd-Pd sites on Pd nanoparticles and individual Pd sites are respectively obtained on the same N-doped carbon coated ZnO support. Compared with Pd-Pd sites and individual Pd sites, Pd-Zn dual sites display much higher activity for ethanol electro-oxidation, exceeding that of commercial Pd/C by a factor of ~24. Further computational studies disclose that Pd-Zn dual sites promote the adsorption of ethanol and hydroxide ion to optimize the electro-oxidation pathway with dramatically reduced energy barriers, leading to the superior activity. This work provides valuable clues for developing high-performance ethanol electro-oxidation catalysts for fuel cells.

High-performance Pd nanocatalysts based on the novel N-doped Ti3C2 support for ethanol electrooxidation in alkaline media

In this article, the novel N-doped Ti3C2 support Pd-based catalyst (Pd/N-Ti3C2-28 h) is successfully prepared by suitable HF-etching and NH3.H2O doping, which possess the conspicuous lamellar morphology and uniform metal Pd distribution. The Pd/N-Ti3C2-28 h with N-doping has the higher content of Pd (~5.33 at%) than that of without N-doping (~1.38 at%) under the same mass of Pd loading. Being explored as the catalyst for ethanol electrooxidation in alkaline medium, the Pd/N-Ti3C2-28 h catalyst exhibits the higher electrochemically active surface areas, ethanol oxidated current densities (~36.71 mA.cm−2) and electrochemical stability than those of the Pd/Ti3C2-28 h, the other Pd/N-Ti3C2 catalysts with different HF-etching time (20,24 and 32 h), and the commercial Pd/C (j = ~12.73 mA.cm−2). Such excellent electrocatalytic performance can be ascribed to synergy of obvious layer-structure of the Ti3C2 support and the NH3.H2O doping, which lead to the higher binding energy and more electron transfer of the metal Pd and Ti3C2, thereby improving the Pd loading on the Ti3C2. And the current densities after 200 redox cycles of Pd/Ti3C2-28 h can retain 78.3% of the maximum capacity, demonstrating the high cycle stability. Thus, the Pd/N-Ti3C2-28 h can become the potential candidates as the anode catalyst for the ethanol electrooxidation in alkaline medium.