Electrocatalytic Oxidation Of Methanol Research Articles

Mechanisms of formation and shape control of pentagonal Pd-nanostars and their unique properties in electrocatalytic methanol oxidation and membrane separation of high-purity hydrogen

Membranes on palladium alloy basis with surface modified by nanoparticles with high catalytic activity are useful in deep hydrogen purification and single-stage process of high-purity hydrogen production. This paper reports the development and improvement of methods for synthesis of Pd-based pentatwinned nanoparticles of strictly specified morphology with certain shapes, facets and composition. The competing effect of surfactants and optimization of the halide ions ratio in solution make it possible to direct a particle growth towards formation of pentatwinned Pd-nanostars. Pd–23%Ag coatings synthesized on the surface showed uniquely high peak current density of up to 238 mA cm−2 in alkaline methanol oxidation reaction. This is due to both increased surface area and greater catalytic activity of nanostars’ facets. A record increase in hydrogen permeability of up to 12.5 mmol s−1 m−2 at 100 °C has been achieved for palladium-silver membranes with modified surface. This indicates an acceleration of sorption/desorption stages. The developed method for controlling morphology of nanoscale coatings opens the way to the production of membrane hydrogen filters, which operate at room temperature.

Competitive coordination-induced assembling of Ni-mof/NiFe-ldh heterostructure for enhanced electrocatalytic methanol oxidation

Direct methanol fuel cells (DMFCs) can permit the utilization of noble-metal-free electrocatalysts, which certainly reduces the cost and accelerates their practical implementation. With the exploration of efficient and economical methanol oxidation reaction (MOR) catalysts, Ni-based nanostructures have been recognized as the most promising MOR catalysts in alkaline media. Herein, we construct a novel heterojunction MOR electrocatalyst composed of Ni-based metal-organic framework (Ni-MOF) and NiFe-based layered double hydroxides (LDHs) through a coordination-induced self-assembly strategy. Owing to the synergic effect between Ni and Fe sites, coupled with the effect of hetero-interface, the resultant Ni-MOF/NiFe-LDH composite exhibits remarkable MOR activity in 0.1 M KOH electrolyte with the oxidation current density (32.66 mA cm−2) is 2.65 and 2.44 times higher than that of the primitive NiFe-LDH and Ni-MOF. The excellent stability of the Ni-MOF/NiFe-LDH electrocatalyst has also been confirmed by long-term chronoamperometry (CA) analysis. Our work paves a facile controllable way for fabricating MOF/LDH heterostructure targets on MOR and underlines its potential to boost energy conversion efficiency through the manipulation of synergic components.

New type nanocomposite based on metal-organic frameworks decorated with nickel nanoparticles as a potent electrocatalyst for methanol oxidation in alkaline media

Methanol oxidation reaction (MOR) is used to provide electrical energy via direct methanol fuel cell (DMFC), which requires a practical design of electrocatalysts to accelerate the sluggish MOR. In this study, we successfully fabricated the carbon black nanoparticles/graphite ceramic electrode (CBNPs/GCE) supported metal-organic frameworks (MOFs) and decorated with nickel nanoparticles (NiNPs) as a new type nanocomposite modified electrode (NiNPs/MOFs/CBNPs/GCE) via a chemical and an electrochemical process, respectively. The surface morphology and structure of the synthesized nanocomposite materials and modified electrodes were characterized using field emission scanning electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. Then, the NiNPs/MOFs/CBNPs/GCE was used as a non-platinum electrocatalyst for electrocatalytic oxidation of methanol in alkaline media. The obtained results show the efficient electrocatalytic activity of the NiNPs/MOFs/CBNPs/GCE toward the MOR with high anodic peak current density (Jpa = 34.8 mA cm−2) compared with the other prepared electrocatalysts; MOFs/CCE, NiNPs/CCE, MOFs/CBNPs/GCE, NiNPs/CBNPs/GCE, and NiNPs/MOFs/CCE, due to the synergistic effect of nanocomposite components; NiNPs, MOFs and CBNPs. The prepared electrocatalyst; NiNPs/MOFs/CBNPs/GCE, not only shows a high electrochemically active surface area (ECSA = 2.15 cm2) but also has long-term durability in MOR. In general, it can be said the NiNPs/MOFs/CBNPs/GCE is a promising candidate for application in DMFC.

Constructing Zn-based MOF-MXene nanoarchitectures to stabilize ultrafine Pt nanocrystals with enhanced methanol oxidation performance

Although the development of direct methanol fuel cell technology is regarded as one rational option to against severe energy crises and environmental pollution, the low efficiency and considerable costs of current Pt-based anode catalysts largely impede the broad-scale commercialization. Herein, a convenient bottom-up approach is developed to the spatial construction of ultrafine Pt nanocrystals stabilized on a porous heterojunction matrix built from Zn-based metal organic frameworks and Ti3C2Tx MXene nanolamellas (Pt/ZIF-Ti3C2Tx) through the stepwise solvothermal reactions. The intercalation of metal organic frameworks produces plentiful cavities and channels for the dispersion and immobilization of small-sized Pt nanoparticles, while the incorporation of Ti3C2Tx nanosheets optimizes the Pt electronic structure and ensures a high electron conductivity. As a consequence, the as-acquired Pt/ZIF-Ti3C2Tx nanoarchitectures manifest exceptional electrocatalytic methanol oxidation abilities in terms of a large electrochemically active surface area of 110.5 m2 g−1, a high mass activity of 1900.1 mA mg−1, and preferable long-term stability, all of which are significantly superior to those of conventional Pt/carbon and Pt/unmodified Ti3C2Tx catalysts.

Production of NiCoMo-Supported Ni Foam for Electrocatalytic Oxidation of Methanol: Experimental and RSM Analysis

AbstractThe Ni-, Co-, and Mo-supported Ni foam (NiF–NiCoMo) was produced via galvanostatic method, and electrooxidation of methanol in alkaline medium was examined. The characterization was achieved using field emission scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction analysis. The electrochemical behavior was determined via cyclic voltammetry and chronoamperometry analysis. The contribution of each transition metal to electrocatalytic performance of NiF was monitored via mono, binary, and ternary modifications of each transition metal (Ni, Co, and Mo) for several amounts (5, 10, and 15 μg). Experiments were performed to determine the influence of catalyst amounts, methanol concentration, and scan rate parameters. The impacts of independent parameters on methanol electrooxidation were statistically investigated using Design-Expert software. The ability to analyze multiple parameters with a limited number of experimental performances is one of the method’s key benefits. The developed model showed that 9.41 and 14.03 µg catalyst amounts were the appropriate values for NiF–NiMo and NiF–NiCoMo achieving optimal circumstances, respectively.

Heterointerface engineering of rhombic Rh nanosheets confined on MXene for efficient methanol oxidation

Although metallic rhodium (Rh) is regarded as a promising platinum-alternative anode catalyst of direct methanol fuel cell (DMFC), the conventional “particle-to-face” contact model between Rh and matrix largely limits the overall electrocatalytic performance due to their insufficient cooperative effects. Herein, we report a controllable and robust heterointerface engineering strategy for the bottom-up fabrication of rhombic Rh nanosheets in situ confined on Ti3C2Tx MXene nanolamellas (Rh NS/MXene) via a convenient stereoassembly process. This unique design concept gives the resulting 2D/2D Rh NS/MXene heterostructure intriguing textural features, including large accessible surface areas, strong “face-to-face” interfacial interactions, homogeneous Rh nanosheet distribution, ameliorative electronic structure, and high electronic conductivity. As a consequence, the as-prepared Rh NS/MXene nanoarchitectures exhibit exceptional electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area of 126.2 m2 g−1Rh, a high mass activity of 1056.9 mA mg−1Rh, and a long service life, which significantly outperform those of conventional particle-shaped Rh catalysts supported by carbon black, carbon nanotubes, reduced graphene oxide, and MXene matrixes as well as the commercial Pt nanoparticle/carbon black and Pd nanoparticle/carbon black catalysts with the same noble metal loading amount. Density functional theory calculations further demonstrate that the direct electronic interaction at the well-contacted 2D/2D heterointerfaces effectively enhances the adsorption energy of Rh nanosheets and induces a left shift of the d-band center, thereby making the Rh NS/MXene configuration suffer less from CO poisoning. This work highlights the importance of rational heterointerface design in the construction of advanced noble metal/MXene electrocatalysts, which may provide new avenues for developing the next-generation DMFC devices.

Confining N-Doped Carbon Dots into PtNi Aerogels Skeleton for Robust Electrocatalytic Methanol Oxidation and Oxygen Reduction.

Noble metallic aerogels with the self-supported hierarchical structure and remarkable activity are promising for methanol fuel cells, but are limited by the severe poisoning and degradation of active sites during electrocatalysis. Herein, the highly stable electrocatalyst of N-doped carbon dots-PtNi (NCDs-PtNi) aerogels is proposed by confining NCDs with alloyed PtNi for methanol oxidation and oxygen reduction reactions. Comprehensive electrocatalytic measurements and theoretical investigations suggest the improvement in structure stability and regulation in electronic structure for better electrocatalytic durability when confining NCDs with PtNi aerogels. Notably, the NCDs-PtNi aerogels perform 12-fold higher activity than that of Pt/C and maintain 52% of their initial activity after 5000 cycles toward acidic methanol oxidation. The enhanced stability and activity of NCDs-PtNi aerogels are also evident for oxygen reduction reactions in different electrolytes. These results highlight the effectiveness of stabilizing metallic aerogels with NCDs, offering a feasible pathway to develop robust electrocatalysts for fuel cells.

Electrocatalytic Oxidation of Methanol and Ethanol with 3d-Metal Based Anodic Electrocatalysts in Alkaline Media Using Carbon Based Electrode Assembly.

Homogeneous electrocatalytic systems based on readily available, earth-abundant, inexpensive base metals Ni, Co, and Cr have been formulated for the electro-oxidation of alcohols (methanol and ethanol) that constitute a key half-cell component of direct alcohol fuel cells (DAFCs). Notably, excellent results were obtained for both methanol as well as ethanol electro-oxidation while operating with a half-cell assembly based on all-non-noble working and counter electrode systems consisting of glassy carbon and graphite rod, respectively. Using NaOH as the supporting electrolyte, Ni/Co/Cr metal salts and their bis(iminopyridine) complexes have been used as anodic electrocatalysts for the alcohol half-cell reactions, and among them, catalytic systems based on Co outperformed the corresponding systems based on Ni and Cr. The system comprising CoCl2.·6H2O [10 mM] + NaOH [6 M] at room temperature emerged as the best electrocatalyst for both methanol [5 M] electro-oxidation (ca. 522.5 ± 13.5 mA cm-2 at 1.4 V) and ethanol [5 M] electro-oxidation (ca. 209 ± 25 mA cm-2 at 1.34 V). It was observed that regardless of the starting alcohol, the end product is carbon dioxide, all of which gets trapped as sodium carbonate (up to 97% yield), thereby mitigating any possible hazards of greenhouse gas emission. Inferences obtained from FETEM, FESEM, and EDS analysis of both the electrolyte solution and residues deposited on the electrode surface provide evidence for the mostly homogeneous nature of the reaction mixture with the molecular catalyst being the major contributor toward the electrocatalytic activity apart from the minor role played by trace heterogeneous particles. The current cell assembly operating with non-noble working and counter electrodes utilizing a catalytic system based on an earth-abundant, base metal salt/complex that not only results in good half-cell current densities for high-energy power-source DAFCs but also generates high-value sodium carbonate offers an exciting avenue.

Nanoarchitectonics for modulation on the electronic structure of ultrafine PtRuFe nanowires as robust methanol electrooxidation catalysts

The widespread adoption of Pt-based electrocatalysts in the anode side of direct methanol fuel cell (DMFC) faces challenges stemming from their limited activity, stability, and high cost. Herein, ultrafine PtRuxFey trimetallic nanowires (PtRuxFey NWs) with a diameter of approximately 1.25 nm were synthesized for the electrocatalytic methanol oxidation reaction (MOR). The structure-activity relationship between the electronic structure of PtRuxFey NWs and their electrocatalytic performance was established by meticulously controlling the addition of Ru(acac)3 and Fe(Ac)2. Under optimal conditions, PtRu0.25Fe0.14 NWs displayed remarkable MOR performance, boasting the mass activity (1332.3 mA mgPt−1) and specific activity (1.0 mA cm−2), a 4.0-fold and 1.8-fold enhancement over that of the commercial catalysts. Additionally, after a chronoamperometry test, PtRu0.25Fe0.14 NWs demonstrated a current density 8.3 times higher than that of Pt/C under the same test conditions. The excellent MOR performance of PtRuxFey NWs can be attributed to their one-dimensional and ultrafine structure advantages, the electronic effects of Ru/Fe on Pt, and the bifunctional capabilities. Our research may lead to a simple and controllable strategy that combines various approaches to enhance the performance of Pt-based electrocatalysts in the anode of DMFC.

Platinum Alloys for Methanol Oxidation Electrocatalysis: Reaction Mechanism and Rational Design of Catalysts with Exceptional Activity and Stability

Direct methanol fuel cells have emerged as highly promising energy conversion devices in the past few decades. However, some challenges, such as carbon monoxide (CO) poisoning and unsatisfactory long-term stability, remain for platinum (Pt) as a methanol oxidation reaction (MOR) catalyst. This review covers recent advances in Pt alloy MOR catalysts and provides some insights. This review presents MOR catalytic mechanisms based on CO or non-CO pathways. Typical dimension-based designs of MOR catalysts, such as anisotropic nanowires, metallene, nanoframes, and corresponding rationales for performance enhancements, are introduced. More importantly, some key tuning strategies are elaborated, including intermetallic compound synthesis, interface engineering, and surface facet engineering. High-entropy alloys as an intriguing class of MOR catalysts with favorable prospects are also discussed. Finally, future directions and opportunities are outlined.

Investigation on the electrocatalytic oxidation of alcohol using zinc oxide thin films deposited by pulsed electrodeposition on an indium tin oxide surface

To perform electro-catalytic oxidation of alcohols in an alkaline media, zinc oxide (ZnO) thin films were effectively deposited on indium tin oxide (ITO) substrates using the pulsed electrodeposition (PE) method in a zinc nitrate aqueous solution. Analyses of microstructural, photoelectrochemical, and optical characteristics of ZnO thin films were performed as a function of pulsed electrodeposition parameters. XRD analysis was applied to determine structural properties, and SEM and AFM analysis were used to investigate morphological characteristics. X-ray diffraction analyses revealed that the produced films were polycrystalline and had a (002) preferentially oriented, hexagonal wurtzite structure. The morphology of ZnO has improved in the direction of nanorod films, as evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. UV transmittance data was used using Tauc's relationship to determine the film's bandgap to be 3.26 eV. The photocurrent response shows that ZnO films have high values, at 305.17 A/cm2, and good optical characteristics. The electrocatalytic oxidation of methanol was finally evaluated on the films. After being optimized in the pulsed electrodeposition mode, ZnO thin film characteristics and methanol electrocatalytic oxidation both saw substantial improvements.

NiSe2/CeO2 catalysts from Ce-UiO-66 metal-organic skeletons and their electrocatalytic oxidation of methanol, urea and glycerol.

Hydrogen is a viable alternative energy source to fossil fuels. In order to manufacture enough hydrogen to meet the needs of social growth, finding an alternate energy source that is more effective is essential. Electrochemical water cracking is a more appropriate method for producing hydrogen. The methanol oxidation reaction (MOR), urea oxidation reaction (UOR) and glycerol oxidation reaction (GOR) can be used to replace the anodic oxygen evolution reaction (OER) and indirectly accelerate the hydrogen evolution reaction (HER), which has the advantages of saving energy and reducing environmental pollution. In this study, Ni/CeO2 catalysts were prepared by thermal annealing of MOFs (Ce-UiO-66) containing nickel species and NiSe2/CeO2 nanocrystalline catalysts were obtained through the selenation reaction at different temperatures. The NiSe2/CeO2-450 °C catalysts exhibited superior catalytic performance for the MOR, UOR, and GOR. The MOR showed a peak current density of roughly 186.68 mA cm-2 and a low oxidation potential of around 1.34 V. Similarly, the UOR demonstrated a peak current density of approximately 142.28 mA cm-2 and a low oxidation potential of around 1.32 V. Furthermore, the GOR exhibited a peak current density of approximately 82.56 mA cm-2 and a low oxidation potential of around 1.37 V. NiSe2/CeO2-450 °C could improve electrocatalytic performance for the MOR, UOR, and GOR, which is attributed to the more active sites that were exposed as a result of utilizing MOFs (Ce-UiO-66) as a precursor. Additionally, selenation increased the ability to transfer electrons. This research is crucial for the production of inexpensive, easily accessible transition metals in place of expensive noble metals, for the reduction of wastewater pollution from methanol and urea, and for the creation of effective anodic oxidation electrocatalysts.

PtCu/Pt core/atomic-layer shell hollow octahedra for oxygen reduction and methanol oxidation electrocatalysis.

Engineering effective bifunctional electrocatalysts that outperform the benchmark Pt/C for direct methanol proton exchange membrane fuel cells is desired and challenging. Here, we designed H-PtCu/PtL OH catalysts with a sub-nanometer Pt(111) shell layer featuring Cu- and Co-vacancies, which exhibited high activity in acidic oxygen reduction and methanol oxidation reactions.

Promoting electrocatalytic oxidation of methanol to formate through interfacial interaction in NiMo oxide-CoMo oxide mixture-derived catalysts

Designing efficient, stable, and easily scaled-up catalysts for nucleophile oxidation reactions (NOR) is a key step in promoting the industrial application of NOR. Here, a simple physical mixing strategy is adopted to prepare a mixture of NiMo oxide and CoMo oxide as catalyst for methanol electrocatalytic oxidation reaction (MOR). The mixture exhibits high catalytic activity for MOR and its performance far exceeds that of a single component. The interaction at the contact interface between nickel and cobalt components is clarified through operando electrochemical impedance spectroscopy, in-situ Raman spectroscopy, and a series of electrochemical tests. The interfacial interaction enhances the charge transport and promotes the formation of electrophilic OH* species, which significantly boosts the methanol oxidation reaction. This work provides a new idea for the design of efficient and easily scaled-up catalysts for nucleophile oxidation reactions.

Fe-based “electron pump” involving NiCo-LDH enables robust and highly-selective electrocatalytic methanol oxidation to formic acid

Nucleophile oxidation reactions, represented by the incomplete methanol oxidation reaction (i-MOR) to formic acid, can effectively lower the potential of electrolytic hydrogen production while generating high-value products.

Bimetallic Pt–M (M = Fe, Co, Ni) nanobunches composed of ultrathin nanowires with strong synergy and rich surface defects for enhanced methanol oxidation electrocatalysis

High performance and cost-effective electrocatalysts have been intensively pursued to push forward the commercialization of direct methanol fuel cells (DMFCs).

Design and catalytic performance of Cu/γ-Al2O3 for electrocatalytic methanol oxidation reaction by using density functional theory and molecular dynamics

The electrocatalytic activity of methanol oxidation reaction (MOR) on Cu/γ-Al2O3 and the growth behavior of Cu on γ-Al2O3 are investigated by using density functional theory and molecular dynamics. It is found that the interaction between the Cu3 cluster and γ-Al2O3(110) is stronger than that between the Cu4 cluster and γ-Al2O3(110). Consequently, the d-band center of the Cu3 cluster locates close to the Fermi level compared to the d-band center of the Cu4 cluster, resulting in high electrocatalytic MOR activity on Cu3/γ-Al2O3(110). The electrocatalytic MOR pathway is non-CO pathway on Cu3/γ-Al2O3(110). The highest Gibbs free energy pathway is CH3O* → CH2O*, which the Gibbs free energy is 0.53 eV. To achieve a high proportion of 2D Cu cluster on γ-Al2O3, it is recommended to prepare the catalyst at temperatures below 500 K with Cu loading below 21.78 wt%. These findings provide valuable insights into the design of MOR catalysts.

Tuning the Pt–Ru Atomic Neighbors for Active and Stable Methanol Oxidation Electrocatalysis

Tuning the Pt–Ru Atomic Neighbors for Active and Stable Methanol Oxidation Electrocatalysis

Enhancing methanol oxidation electrocatalysis by Pt/Mo2CTx-rGO ternary hybrid catalyst

Here we report a ternary hybrid catalyst, Pt/Mo2CTx-rGO, for the electrocatalysis of methanol oxidation in direct methanol fuel cells. Two-dimensional Mo2CTx MXene was used to modify reduced graphene oxide (rGO) to obtain a hybrid of Mo2CTx-rGO. Thereafter, ultrafine Pt nanoparticles were dispersed on the hybrid to make a ternary catalyst of Pt/Mo2CTx-rGO. The electrochemical performance of the catalyst was evaluated in 1 M H2SO4 and 2 M methanol electrolyte as a target analyte. Compared with commercial Pt/C, Pt/Mo2CTx-rGO demonstrated 1.5 times larger electrochemically active surface area, 1.9 times higher mass activity, and 33.6 % longer durability. This is because of the strong electronic interaction between Pt and Mo2CTx as well as the large surface area of rGO. This work reports a novel electrocatalyst with high activity and long durability for methanol oxidation, and explore a novel application of Mo2CTx MXene.

Electronic structure engineering of Pt3Co nanoparticles via B, N co-doping of the carbon support boosts electrocatalytic methanol oxidation

Developing highly efficient and durable catalysts for the methanol oxidation reaction (MOR) is crucial to the commercialization and widespread uptake of direct methanol fuel cells (DMFCs). Carbon-supported Pt nanoparticle (NP) catalysts demonstrate high initial activities for MOR, but suffer from electrochemical instability. Herein, nanoalloying and heteroatom-doping strategies were adopted to prepare well-ordered intermetallic Pt3Co NPs anchored on B, N co-doped multiwalled carbon nanotubes, with the developed Pt3Co/BN-MWCNTs electrocatalyst offering high stability for MOR in 0.1 M HClO4. Benefiting from the optimal electronic structure of the ordered Pt3Co NPs and asymmetric electron transfer (B → C → N) in the support, the activity, stability and CO poisoning resistance of Pt3Co/BN-MWCNTs electrocatalyst were significantly enhanced compared to a commercial Pt/C catalyst. Density functional theory (DFT) calculations revealed that electronegativity differences between Pt and Co enable significant charge redistribution, lowering the energy barriers and potentials for the oxidation of the *CO intermediate by OH* species, greatly enhancing MOR kinetics under acid conditions. Further, B, N co-doping of the MWCNTs strengthened the interaction with the Pt3Co NPs, further boosting MOR performance by suppressing Pt3Co dissolution into the electrolyte. The findings of this work are expected to be applied in catalyst design for a wide range of energy conversion devices.