Catalysts For Methanol Oxidation Research Articles

Constructing Efficient CuAg Nanoalloys on Ce0.90In0.10Oδ for Methanol Deep Oxidation Catalysis at Low Temperature.

So far, it is still extremely challenging to develop an efficient catalyst for deep oxidation of methanol at low temperature. Herein, we report the construction of the highly dispersed CuAg alloy on the surface of Ce0.90In0.10Oδ nanorods support for catalyzing methanol deep oxidation. The composition, structure and properties of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the CuxAg100-x/Ce0.90In0.10Oδ alloy catalysts exhibit superior catalytic activity and stability compared to pure Ag/Ce0.90In0.10Oδ, with the highest activity observed for Cu40Ag60/Ce0.90In0.10Oδ, accompanied by the light-off temperature (T50) and full conversion temperature (T90) of 115 and 145 °C, respectively. This is attributed to the synergistic effect of CuAg alloy, which results in electron transfer, generating more Ag0, and enhanced interaction between CuAg alloy and the support, leading to increased Ce3+ content and higher oxygen vacancy concentration. This work successfully applies CuAg alloy catalysts in thermo-catalytic reaction, offering promising prospects for CuAg alloy catalysts in the methanol deep oxidation.

Construction of MOF-5 derived ZnO composites porous carbon supported Pd nanoparticles as highly stable catalyst for methanol and ethanol oxidation

The preparation of highly active and stable Pd-based catalysts for direct alcohol fuel cells (DAFC) is hampered by inefficient utilization of the active sites, susceptibility to CO poisoning, poor stability, and relatively slow reaction kinetics. Herein, the stability and anti-toxicity of the catalysts (Pd/ZnO/MDC) are tuned by loading Pd nanoparticles on the carbon-coated ZnO support, achieving efficient electrocatalysis for methanol and ethanol oxidation reaction (MOR and EOR). TEM result shows the ZnO is covered by the carbon layer formed outside of MOF-5 derived porous carbon, which can prevent it from dissolving under harsh conditions. The mass activities of the well-tuned catalyst Pd/ZnO/MDC(800) for MOR and EOR are 931.83 mA/mg and 1838.30 mA/mg, respectively. It is due to the improved electron transport efficiency between the Pd and ZnO, and the enhanced stability by carbon layer outside the ZnO. It is also found that the onset potential and the peak potential of Pd/ZnO/MDC(800) (−0.813 V, −0.228 V) in CO stripping experiment in MOR are more negative than Pd/MDC(800) (−0.261 V, −0.215 V). This result indicates that the existence of ZnO helps to provide surface hydroxyl group, which promotes the oxidation of the intermediates. This work indicates provides a feasible idea for DAFC catalyst design and construction.

Enhanced Catalytic Performance and Tolerance to Carbon Monoxide Poisoning of CoO/PtPd/r‐GO Nanocomposite Thin Film for Methanol Fuel Cells

This study presents the facile synthesis of CoO/PtPd and CoO/PtPd/reduced‐graphene oxide (r‐GO) nanocomposites, highlighting their significant role in methanol fuel cells. To create a CoO/PtPd thin film at the toluene/water interface, we employed NaBH4 to effectively reduce PtCl2(COD), PdCl2(COD), and Co (acac)3 (COD = cis,cis‐1,5‐ cyclooctadiene, acac = acetylacetonate). The two nanocomposites were analyzed using XRD, FE‐SEM, AFM, XPS, BET, and TEM techniques. In the electrooxidation of methanol in the anodic part of fuel cell, cobalt (II) oxide can serve as an oxygen source in the catalytic oxidation of carbon monoxide (CO) or it can play a role in producing the HO‐CoO intermediate to facilitate the oxidation of CO‐PtPd to carbon dioxide (CO2). This reaction can help eliminate CO, which is a common poison for Pt‐based catalysts in methanol oxidation. Our research reveals significant improvements in current densities and catalyst tolerance when using the CoO/PtPd/r‐GO nanocomposite thin film. The observed current density for CoO/PtPd/r‐GO is 263.33 mA.cm−2, surpassing the reported value of 30.00 mA.cm−2 for PtPd/r‐GO. The jf/jb ratios, commonly used to evaluate catalyst tolerance, are approximately 2.80 for CoO/PtPd and 4.98 for CoO/PtPd/r‐GO, in contrast to ratios larger than 0.99 for ETEK Pt and 0.58 for other types of commercial Pt/C. These findings indicate that the CoO/PtPd/r‐GO thin film exhibits enhanced catalytic performance and improved tolerance to CO poisoning. Furthermore, the power output calculated for CoO/PtPd/r‐GO is 104.5 mW·cm−2, which is comparable to the reported value of 48.03 mW·cm−2 for commercial Pt/C. These results demonstrate the potential of the CoO/PtPd/r‐GO nanocomposite thin film as a promising alternative to traditional catalyst materials in methanol fuel cells.

A versatile non-precious metal based electrode material endowed by layer-on-layer structure for methanol oxidation and supercapacitor applications

A high-performance non-noble metal-based electrode is the need of the hour to resolve the challenge of huge energy demand. Energy conversion and storage devices are the two ways to tackle this challenge. In this context, porous and non-noble metal-based electrodes NiCo2O4 (NCO), NiCo2O4/NiO (CNO) and NiCo2O4/NiO/rGO (CNOG) are developed as a bifunctional electrode for supercapacitor and methanol fuel cell applications. The binary composite of NiCo2O4 with NiO increases the redox sites and enhances its electrochemical activity. The low conductivity and problem of aggregation of transition metal oxides are overcome by developing a hybrid nanocomposite of NiCo2O4/NiO with reduced graphene oxide (rGO). The layer-on-layer morphology of CNOG, and the interfacial interactions among NiCo2O4 nanoflakes, NiO nanoparticles and rGO nanosheets increase the specific surface area of the hybrid, which leads to enhanced ion penetration into the active sites. CNOG acts as a potential anode catalyst for methanol oxidation with excellent structural stability. It exhibits a high methanol oxidation current density with low onset potential and faster kinetics. Symmetric supercapacitor CNOG//CNOG delivers specific capacitance of 59.4989 F/g, energy and power density of 6.69 Wh/kg and 698 W/kg respectively at 3 M KOH aqueous electrolyte. The solid-state symmetric supercapacitor (SSSC) using PVA/KOH electrolyte allows broader potential window, thereby outperforming the aqueous electrolyte. The SSSC exhibits specific capacitance of 88.8 F/g, energy and power density 20.84 Wh/kg and 1003 W/kg respectively at the same current density.

MOFs-derived TiO2 on N-doped carbon materials with high concentration of oxygen vacancies as Pt supports and co-catalysts for methanol electrooxidation

MIL-125(Ti)–NH2 was pyrolyzed in N2 and H2/Ar gas to prepare N-doped carbon materials containing TiO2 (TiO2-NC). XPS, ESR and Raman spectra analysis showed that higher concentration of oxygen vacancies were created on the surface of TiO2 in H2/Ar gas, which provided more anchor sites for the nucleation of Pt and enhanced the interaction between Pt and TiO2. Therefore, the mass activity/specific activity of Pt/(TiO2-NC)HA catalysts for methanol oxidation was 510.7 mA mg−1Pt/2.84 mA cm−2Pt, which was 3.1/1.4 times that of Pt/(TiO2-NC)N catalysts. Due to the enriched OHads on the suface of TiO2 and the strong metal-support interaction between TiO2 and Pt, Pt/(TiO2-NC)HA catalysts exhibited stronger resistance to COads poisoning than commercial JM-Pt/C catalysts, thus showing more excellent catalytic activity and stability.

Efficient and stable PtFe alloy catalyst for electrocatalytic methanol oxidation with high resistance to CO

Direct methanol fuel cells (DMFC) are widely considered to be an ideal green energy conversion device but their widespread applications are limited by the high price of the Pt-based catalysts and the instability in terms of surface CO toxicity in long-term operation. Herein, the PtFe alloy nanoparticles (NPs) with small particle size (∼4.12 nm) supported on carbon black catalysts with different Pt/Fe atomic ratios (Pt1Fe2/C, Pt3Fe4/C, Pt1Fe1/C, and Pt2Fe1/C) are successfully prepared for enhanced anti-CO poisoning during methanol oxidation reaction (MOR). The optimal atomic ratio of Pt/Fe for the MOR is 1:2, and the mass activity of Pt1Fe2/C (5.40 A mg−1Pt) is 13.5 times higher than that of conventional commercial Pt/C (Pt/C-JM) (0.40 A mg−1Pt). The introduction of Fe into the Pt lattice forms the PtFe alloy phase, and the electron density of Pt is reduced after forming the PtFe alloy. In-situ Fourier transform infrared results indicate that the addition of oxyphilic metal Fe has reduced the adsorption of reactant molecules on Pt during the MOR. The doping of Fe atoms helps to desorb toxic intermediates and regenerate Pt active sites, promoting the cleavage of C–O bonds with good selectivity of CO2 (58.1%). Moreover, the Pt1Fe2/C catalyst exhibits higher CO tolerance, methanol electrooxidation activity, and long-term stability than other PtxFey/C catalysts.

The facile production of Fe2O3-biochar electrocatalyst for methanol oxidation reaction

In this study, the facile-green method was applied for the production of electroactive composite anode material. For this purpose, biochar was produced via pyrolysis of Pinus nigra (PN) sawdust in a stainless-steel reactor at 300, 400 and 500 °C with 10 °C/min heating rate. The Fe2O3 particles were fabricated via the green synthesis method. The Fe2O3-biochar electrocatalyst was operated on Ni foam electrode and the potential application as an anode for methanol fuel cell was investigated in an alkaline medium. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller analysis (BET), and attenuated total reflectance Fourier transform infrared spectroscopy (FTIR/ATR) were used to characterize the morphology of the electrocatalyst samples. The electrochemical measurements of electrocatalyst samples were achieved via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and chronoamperometry (CA). The enlarged surface area of biochar enabled the formation of more electroactive sites for methanol electrooxidation and favorable structures of biochar could support to increased electrocatalytic activity of catalysts for methanol oxidation and produce favorable matrices for Fe2O3 loading. The obtained results demonstrate that the electrooxidation of methanol occurred at 0.36 V. The favorable structures of biochar acted as a support, enhancing the electrocatalytic activity of Fe2O3 for methanol oxidation. The electrocatalyst demonstrated remarkable activity with almost 4 A g−1 current density at 0.55 V. The Rct values were 0.73 Ω and 0.45 Ω at 0.55 V, for Ni foam and Ni foam/Fe2O3-biochar, respectively. Long-term measurements demonstrated that the Ni foam/Fe2O3-biochar catalysts was remarkably stable, with a 4 % difference in current before and after the CA analysis.

In situ growth of Ni/Ni3S2–MoO2 nanocrystals on carbon cloth for the enhanced electrocatalytic oxidation of methanol

The rational design and construction of high-performance Ni-based methanol oxidation catalyst is the key technology for direct methanol fuel cell (DMFC). In this work, Ni/Ni3S2–MoO2@CC composite is constructed by in-situ growth of Ni/Ni3S2–MoO2 nanoparticles on carbon cloth (CC) by a two-step method, which has excellent activity and stability for methanol oxidation reaction (MOR), that is, the current density (j) can reach 240.08 mA cm−2 at the potential of 1.67 V. The potentials at different j are 10 mA cm−2@1.37 V and 100 mA cm−2@1.50 V, respectively. Meanwhile, the retention rate of j is 90.36 % after 12 h CA stability test. Based on density functional theory (DFT) calculation, the excellent properties of Ni/Ni3S2–MoO2@CC composite are mainly attributed to its higher conductivity and higher carrier density accelerate the charge transfer in the MOR process, its Ni and Mo sites facilitate the adsorption of methanol as a reactant and desorption of carbon dioxide as a product, thus promoting the kinetics of MOR. In addition, the reaction mechanism of MOR on the Ni/Ni3S2–MoO2@CC is more likely to follow the formation path of CO* intermediates. This work provides a feasible route for the synthesis of high performance electrocatalysts for the MOR.

Synthesis of Ni3 B/Ni via Vacuum-Induced for Ultrahigh Stable and Efficient Methanol Oxidation.

Designing efficient catalysts to promote the electrochemical oxidation of anodes is the core of the development of electrochemical synthesis technologies, such as HER and CO2 RR. Here, a novel vacuum induction strategy is used to synthesize nickel boride/nickel (Ni3 B/Ni) heterostructure catalyst for electrochemical oxidation of methanol into formic acid. The catalyst has extremely high reactivity (only 146.9mV overpotential at 10mAcm-2 , the maximum current density reaches 555.70mAmg-1 and 443.87mAcm-2 ), ultra-high selectivity (Faraday efficiency of methanol conversion to formic acid is close to 100%), and ultra-long life (over 50h at 100mAcm-2 ). In-suit electrochemical impedance spectroscopy proved that MeOH is oxidized first and inhibits the phase transition of the electrocatalyst to the high-valent electrooxidation products, which not only enables the high selectivity of MeOH oxidation but also ensures high stability of the catalyst. The mechanism studies by density functional theory calculations show that the potential determining step, the formation of *CH2 O, occurs most favorably in the Ni3 B/Ni heterostructure. These results provide references for the development of MeOH oxidation catalysts with high activity, high stability, high selectivity, and low cost.

Ultra-Small Ceria Nanocrystals at Carbon Surface Synthesized by Ultrasound Sonication: A Study of Highly Active Platinum-Cerium Bifunctional Catalysts for Methanol Oxidation and Oxygen Reduction

ABSTRACT Cerium (IV) oxide (called ceria) has gained a lot of interest from researchers due to its high oxygen storage capacity (1) and high tolerance toward CO-like intermediates of methanol oxidation reaction (MOR) (2,3). In our previous study (4), the ceria crystals were synthesized by the modified solvothermal synthesis with urea (5) and grain size of ceria was around 30 µm, even if the crystallite size was only 11 nm. However, even this huge grain-size CeOx particles contributed insignificantly to the catalytic synergetic effect of ceria at the PtCe catalysts toward MOR.The parameters influencing the deposition of Pt nanoparticles (NPs) on the ceria-carbon support by the ethylene glycol (EG) reduction method were investigated in previous study (4). It was found that the influence of energy supply methods on the reaction system needs to be simplified to control the nucleation and growth of Pt NPs better.Although the role of catalytically active components (Pt and CeOx) in catalyst is important, the structure of carbon support affects the catalytic behaviour of the catalyst significantly. The chromium carbide-derived carbon, noted as C(Cr-CDC), synthesized in our previous study (6) is active materials toward oxygen reduction reaction in 0.1 mol dm─3 KOH due to its high number of the active sites at the surface, large specific surface area, and unique micro-mesoporous structure. Therefore, it is a good support material for this study.The purpose of this study was to synthesize a ceria with small grain size, improve the activity of Pt NPs synthesized by tuning the parameters of EG reduction method, and compare the activity of the novel PtCe/C(Cr-CDC) materials and PtCe/C (commercial Ketjenblack carbon) materials.In detail, the ceria-carbon materials were synthesized firstly by ultrasound sonication method in the mixture of EG and sodium hydroxide solutions, called sonochemical method. Later, the Pt NPs were deposited onto the ceria-carbon materials by EG reduction method using the refluxing system. All the materials were characterized with thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) methods. All the PtCe/C materials were measured in the 3-electrode system in 0.5 mol dm─3 H2SO4 and in a mixture of 0.5 mol dm─3 H2SO4 + 1 mol dm─3 CH3OH to investigate the electrochemical behaviour and MOR activity, respectively.The results of XRD and SEM-EDX revealed that it was possible to synthesize the ultra-small ceria NPs by the sonochemical method. The crystallite size is smaller than 2 nm. EDX confirmed the presence of cerium in measuring areas, however, the grain size of ceria in ceria-carbon was too small to be revealed with SEM. The TGA confirmed that all cerium was deposited onto carbon with approximately 11 wt. % of the total ceria-carbon weight. Besides, XRD and TGA also confirmed the success of Pt deposition method. The electrochemical activity at PtCe/C materials revealed high electrochemically active surface area value (55-80 mPt 2 gPt −1). ACKNOWLEDGEMENT This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011) and Personal Research Grant PRG676. The SEM-EDX measurements were conducted using the NAMUR+ core facility funded by the Estonian Research Council (TT 13). REFERENCES E. Antolini and J. Perez, Int. J. Hydrog. Energy, 36, 15752–15765 (2011).S. Dai, J. Zhang, Y. Fu, and W. Li, New J. Chem., 42, 18159–18165 (2018).D. Y. Chung, K.-J. Lee, and Y.-E. Sung, J. Phys. Chem. C, 120, 9028–9035 (2016).H. Q. V. Nguyen, J. Nerut, H. Kasuk, M. Härmas, P. Valk, T. Romann, M. Koppel, P. Teppor, J. Aruväli, O. Korjus, O. Volobujeva, and E. Lust, J. Solid State Electrochem. (2022).S. B. Atla, M.-N. Wu, W. Pan, Y. T. Hsiao, A.-C. Sun, M.-J. Tseng, Y.-J. Chen, and C.-Y. Chen, Mater. Charact., 98, 202–208 (2014).H. Q. V. Nguyen, J. Nerut, H. Kasuk, V. Grozovski, T. Thomberg, I. Tallo, R. Palm, M. Koppel, T. Romann, R. Härmas, J. Aruväli, M. Külaviir, and E. Lust, Russ. J. Electrochem., 58, 781–797 (2022).

Efficient bi-functional catalysis of coupled MoSe2 nanosheet/Pt nanoparticles for methanol-assisted water splitting

Efficient metal-support interaction induced high catalysis performance plays a significant role in energy conversion reactions. Herein, two-dimensional (2D) MoSe2 nanosheet-coupled Pt nanoparticles as efficient bi-functional catalysts were demonstrated for hydrogen production from the methanol-assisted water-splitting reaction. The oxophilic MoSe2 component with 2D structures optimized the adsorption of CO* and H* on Pt sites as demonstrated by spectroscopic and theoretical analysis, which resulted in enhanced catalytic ability in methanol-assisted water splitting reaction. The peak current density was 2.5 times higher than that of commercial Pt/C catalyst for methanol oxidation and a small overpotential of 32 mV was demanded to achieve a current density of 10 mA cm−2 for hydrogen evolution reaction in the methanol-containing electrolyte. When serviced as both cathode and anode, a low cell voltage of 0.66 V was required at 10 mA cm−2, significantly lower than that of 1.75 V required for water splitting. The high performance can be attributed to the oxophilicity of MoSe2 and their strong metal-support interaction that promoted the charge transfer and anti-CO poisoning of Pt sites. This work would be instructive for the development of novel bi-functional catalyst platforms for methanol-assisted water splitting in hydrogen production.

Constructing a CrCoNi medium entropy alloy coordinated Pt ultrathin film as durable electrocatalysts for methanol oxidation reaction

As high-efficiency anode methanol oxidation catalysts, platinum-based materials have always occupied a dominant place since the inception of direct methanol fuel cells (DMFCs). However, because of the strong adsorption of intermediates, Pt-active centers are easily poisoned and induce serious activity loss. Here, we investigate the same commonality of the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) mechanism in Pt/CrCoNi complex catalysts and establish a relationship between them to help screen appropriate synergistic materials and reduce activity loss. With this strategy, the OER activity of Pt/CrCoNi is modified via temperature and oxygen pressure control, and the OER overpotential and MOR durability show a positive correlation. The MOR performance of the final optimized Pt/CrCoNi (7.5–225 Torr oxygen pressure and 400 °C annealing, OA) film reaches an advanced level in the Pt-based MOR catalysts and shows a mass activity of 3785 A gPt-1, as well as a good durability of 50000 s in the alkaline solution.

Synthesis of highly efficient Cu-PtRu ternary metal catalyst for methanol oxidation

Development of remarkably catalytic activity and CO resistance catalyst has become a focus for methanol oxidation. In this study, the irregular polyhedral of Cu was synthesized by simple electrochemical deposition method. Then Pt-Ru alloy nanoclusters were uniformly deposition on Cu polyhedra to prepare Cu-PtRu ternary alloy materials. The morphology and structure of the ternary alloy were studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). Electrochemical results showed that Cu-PtRu exhibited favorable catalytic capacity and high CO resistance for methanol oxidation. In various proportion of Pt-Ru, Cu-Pt5.2Ru1 showed the highest electrocatalytic activity (638.2 mA mgPt−1) for methanol oxidation, which was 2.2 and 2.84 folds relative to commercial Pt/C (Pt wt.20%) and PtRu/C (Pt wt.30%), respectively. Therefore, Cu-Pt5.2Ru1 might be used as a novel structure electro-catalyst for methanol oxidation.

Multiple cyclic voltammetry of noble-metal-based alloy electrocatalyst for methanol oxidation: Revealing a universal criterion of auxiliary metal selection and a new mechanism of activity enhancement

Methanol oxidation catalysts are mainly based on Pt/Pd-based alloys, and various complex strategies are often employed to improve their activity. It is a common practice to clean the contaminants adsorbed on the surface of noble-metal-based catalysts by multiple cyclic voltammetry (MCV) prior to activity test. In this study, we find that this common practice can enhance the activity of noble-metal-based alloy catalysts for methanol oxidation by up to nearly three times. For the first time, a universal criterion is proposed for screening auxiliary metal elements that can significantly improve the activity by this simple practice: oxidable but insoluble in the potential range of CV. Also for the first time, a new activity enhancement mechanism by this common MCV is revealed: noble metal migration, valence state change and oxygen vacancy. As a proof-of-concept, Pt-Sn and Pd-CoSn exhibit high catalytic activity and durability after MCV, making the performance of flexible methanol fuel cells more prominent as well. This work puts forward a universal criterion of auxiliary metal selection and a new mechanism for the remarkably improved activity obtained by MCV, which provides a facile method for obtaining a series of highly active catalysts in the ethaline electrocatalysis field.

Ultra-Small Ceria Nanocrystals at Carbon Surface Synthesized by Ultrasound Sonication: A Study of Highly Active Platinum-Cerium Bifunctional Catalysts for Methanol Oxidation and Oxygen Reduction

In this study, 0.7 nm CeO2 crystallites were synthesized by a sonochemical method to prepare a highly active PtCe catalyst material for methanol oxidation and oxygen reduction reaction. The obtained materials contained Pt nanoparticles with a crystallite size of 1 nm and were well dispersed on the surface of carbon material. This is confirmed by ECSA as high as 89 mPt 2 gPt −1. The PtCe materials synthesized on Ketjenblack carbon with small CeO2 were more favorable with methanol oxidation (MOR) in the mixture of 0.5 mol dm−3 H2SO4 and 1 mol dm−3 CH3OH. The MOR mass activity was as high as 200 A gPt −1 after 1-hour chronoamperometry measurement at 0.85 V vs RHE. The PtCe synthesized on chromium carbide-derived carbon material was more favorable to oxygen reduction (ORR) in 0.1 mol dm−3 HClO4 saturated oxygen. The ORR mass activity at 0.9 V vs RHE was 304 A gPt −1. The Pt deposition method was optimized and repeatable.

Enhanced methanol oxidation activity of porous layered Ni/CeO2@CN nanocomposites in alkaline medium

The performance of direct methanol fuel cells (DMFC) partly depends on the development of economical and efficient methanol oxidation catalyst. Here, porous layered Ni/CeO2@CN-T composites were prepared by complexation and pyrolysis two-step methods. The optimal Ni/CeO2@CN-600 for methanol oxidation reaction (MOR) requires only 1.361 V at the current density (j) of 10 mA cm−2, and the j is as high as 229.56 mA cm−2 at 1.642 V, superior to those of the nickel-based catalysts reported. The excellent properties of Ni/CeO2@CN-600 are mainly attributed to the electronic interaction between Ni and CeO2, the uniform dispersion of Ni and CeO2 nanoparticles and its porous layered structure. Meanwhile, it has better stability after 12 h i-t tests. The CO poisoning experiments showed that the anti-CO poisoning ability of Ni/CeO2@CN-600 was obviously stronger than that of Pt/C catalyst in alkaline medium. Finally, the density functional theory (DFT) calculation shows the superior activity of Ni/CeO2 catalysts for MOR is mainly attributed to the higher adsorption energy of Ni/CeO2 for CH3OH and the lower energy barrier.

SO2-tolerant mesoporous iron oxide supported bimetallic single atom catalyst for methanol removal

Among the single-atom catalysts (SACs), the bimetallic single-atom catalysts play an increasingly promising role in the oxidative removal of volatile organic compounds (VOCs) due to their high efficiency. However, it remains a significant challenge to resist SO2 poisoning in industrial applications. In this work, we report (i) the synthesis of three-dimensionally ordered mesoporous Fe2O3-supported bimetallic AuPt single-atom (denote as Au1Pt1/meso-Fe2O3) catalyst via a modified polyvinyl alcohol-protected reduction route; (ii) catalytic performance of the catalysts for methanol oxidation; and (iii) catalytic and SO2-resistant mechanism. It was found that compared with Pt1/meso-Fe2O3 and Ptnp/meso-Fe2O3, Au1Pt1/meso-Fe2O3 exhibited better catalytic activity for methanol combustion, with the temperature at 90% methanol conversion, TOFnoble metal at 120 °C, and apparent activation energy being 137 °C at a space velocity of 20 000 mL g–1 h–1, 6.51 × 10–2 s–1, and 36 kJ mol− 1, respectively. The enhanced activity was associated with the improved reducibility, methanol adsorption ability, and strong interaction between noble metal and support. The reaction pathway was deduced to follow a sequence of methanol → methoxy species → formaldehyde → formic acid → CO2 and H2O. Furthermore, the order of SO2 resistance was Au1Pt1/meso-Fe2O3 > Pt1/meso-Fe2O3 > Ptnp/meso-Fe2O3. The good SO2 resistance of the Au1Pt1/meso-Fe2O3 catalyst was attributed to the Au−Pt bimetallic single atoms uniformly dispersed on the meso-Fe2O3 with the strong ability of sulfate decomposition and the protection of the active sites by meso-Fe2O3 as a sacrificial site. This work presents a novel way for developing high-performance catalysts for VOCs elimination in the presence of SO2.

Platinum-nickel bimetallic catalyst doped with rare earth for enhancing methanol electrocatalytic oxidation reaction

Platinum (Pt) is often used as anodic catalyst for direct methanol fuel cell (DMFC). However, platinum is difficult to achieve large-scale application because of its low stability and high cost. In this work, the electrocatalytic activity and stability of the Pt-based catalyst for methanol oxidation (MOR) are significantly improved by adding Ce and Ni to the catalyst. Additionally, the rare earth element-Pr (Dy) is also chosen to be added into the catalysts for comparison. A series of PtMNi (M = Ce, Pr, Dy) catalysts are prepared by impregnation and galvanic replacement reaction methods using carbon black as support. The electrocatalytic mass activity of PtCeNi/C, PtDyNi/C, PtPrNi/C and Pt/C is 3.92, 1.86, 1.69 and 0.8 A mgPt−1, respectively. The mass activity of these the above four catalysts after stability measurement is 3.14, 1.49, 1.27 and 0.72 A mgPt−1. Among them, PtCeNi/C has the highest catalytic activity. These as-prepared catalysts are also characterized by various analyzing techniques, such as TEM, HRTEM, XRD, XPS, ICP-OES, STEM, STEM-EDS elemental mapping and line-scanning etc. It shows that PtCeNi/C exhibits best catalytic activity (3.92 A mgPt−1) among the as-obtained catalysts, 4.9 times higher than that of commercial Pt/C (0.8 A mgPt−1). PtCeNi/C is also with excellent anti-CO poisoning ability. The outstanding catalytic performance of PtCeNi/C for the MOR is mainly attributable to uniform-sized PtCeNi nanoparticles, uniform Ni, Ce and Pt element distribution, and electron interaction among Pt-, Ni- and Ce-related species (electron transferring from Pt to CeO2).

Facile synthesis of dendritic PtAu@Pt heterostructure nanocatalysts supported on carbon towards methanol electrooxidation

The design of cost-efficient catalysts for the electrooxidation of liquid fuel is now highly desirable for the commercial application of direct alcohol fuel cells. In view of this, we herein reported a simple and one-pot chemical strategy for synthesis of PtAu@Pt nanodendrite on carbon support (PtAu@Pt/C) with Pt/Au core Pt shell heterostructures in amphiphilic triblock copolymer-water system. The preparation process is one-step, free of additives and stabilizers. The structure information and electrocatalytic activity of the prepared PtAu@Pt/C composites were widely analyzed by transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The catalytic activity of bimetallic PtAu@Pt/C catalyst for methanol oxidation (MOR) is higher than that of commercially available Pt/C (JM), and the optimal Pt-to-Au ratio is 3:1, and the nanocatalyst of PtAu@Pt/C (3:1) possesses high stability and durability. The improvement of electrocatalytic activity may be attributed to the effective surface structure of Pt-modified PtAu nanoparticles, which have a higher utilization of Pt in the surface reaction for methanol electrooxidation.

Molten Salts Approach of Poly(vinyl alcohol)-Derived Bimetallic Nickel-Iron Sheets Supported on Porous Carbon Nanosheet as an Effective and Durable Electrocatalyst for Methanol Oxidation.

The preparation of metallic nanostructures supported on porous carbon materials that are facile, green, efficient, and low-cost is desirable to reduce the cost of electrocatalysts, as well as reduce environmental pollutants. In this study, a series of bimetallic nickel-iron sheets supported on porous carbon nanosheet (NiFe@PCNs) electrocatalysts were synthesized by molten salt synthesis without using any organic solvent or surfactant through controlled metal precursors. The as-prepared NiFe@PCNs were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction, and photoelectron spectroscopy (XRD and XPS). The TEM results indicated the growth of NiFe sheets on porous carbon nanosheets. The XRD analysis confirmed that the Ni1-xFex alloy had a face-centered polycrystalline (fcc) structure with particle sizes ranging from 15.5 to 30.6 nm. The electrochemical tests showed that the catalytic activity and stability were highly dependent on the iron content. The electrocatalytic activity of catalysts for methanol oxidation demonstrated a nonlinear relationship with the iron ratio. The catalyst doped with 10% iron showed a higher activity compared to the pure nickel catalyst. The maximum current density of Ni0.9Fe0.1@PCNs (Ni/Fe ratio 9:1) was 190 mA/cm2 at 1.0 M of methanol. In addition to the high electroactivity, the Ni0.9Fe0.1@PCNs showed great improvement in stability over 1000 s at 0.5 V with a retained activity of 97%. This method can be used to prepare various bimetallic sheets supported on porous carbon nanosheet electrocatalysts.