Mechanism and electrocatalysis in the direct methanol fuel cell

Recent advancements and prospects in noble and non-noble electrocatalysts for materials methanol oxidation reactions

The direct methanol fuel cell (DMFC) represents a highly promising alternative power source for small electronics and automobiles due to its low operating temperatures, high efficiency, and energy density. The methanol oxidation process (MOR) constitutes a fundamental chemical reaction occurring at the positive electrode of a DMFC. Pt-based materials serve as widely utilized MOR electrocatalysts in DMFCs. Nevertheless, various challenges, such as sluggish reaction rates, high production costs primarily attributed to the expensive Pt-based catalyst, and the adverse effects of CO poisoning on the Pt catalysts, hinder the commercialization of DMFCs. Consequently, endeavors to identify an alternative catalyst to Pt-based catalysts that mitigate these drawbacks represent a critical focal point of DMFC research. In pursuit of this objective, researchers have developed diverse classes of MOR electrocatalysts, encompassing those derived from noble and non-noble metals. This review paper delves into the fundamental concept of MOR and its operational mechanisms, as well as the latest advancements in electrocatalysts derived from noble and non-noble metals, such as single-atom and molecule catalysts. Moreover, a comprehensive analysis of the constraints and prospects of MOR electrocatalysts, encompassing those based on noble metals and those based on non-noble metals, has been undertaken.

Improvement of Qualitative Analyses of Aliphatic Alcohols Using Direct Catalytic Fuel Cell and Chemometric Analysis Format

Direct catalytic methanol fuel cells (DCMFCs) have been studied for several years for energy conversion. Less extensive is the investigation of their analytical properties. In this paper, we demonstrate that the behavior of both the discharge and charger curves of DCMFCs depends on the chemical composition of the solution injected in the fuel cell. Their discharge and charge curves, analyzed using a chemometric data fusion method named ComDim, enable the identification of various types of aliphatic alcohols diluted in water. The results also show that the identification of alcohols can be obtained from the first portion of the discharge and charge curves. To this end, the curves have been described by a set of features related to the slope and intercept of the initial portion of the curves. The ComDim analysis of this set of features shows that the identification of alcohols can be obtained in a time that is about thirty times shorter than the time taken to achieve steady-state voltage.

Investigating the role of undercoordinated Pt sites at the surface of layered PtTe2 for methanol decomposition

Transition metal dichalcogenides, by virtue of their two-dimensional structures, could provide the largest active surface for reactions with minimal materials consumed, which has long been pursued in the design of ideal catalysts. Nevertheless, their structurally perfect basal planes are typically inert; their surface defects, such as under-coordinated atoms at the surfaces or edges, can instead serve as catalytically active centers. Here we show a reaction probability > 90 % for adsorbed methanol (CH3OH) on under-coordinated Pt sites at surface Te vacancies, produced with Ar+ bombardment, on layered PtTe2 - approximately 60 % of the methanol decompose to surface intermediates CHxO (x = 2, 3) and 35 % to CHx (x = 1, 2), and an ultimate production of gaseous molecular hydrogen, methane, water and formaldehyde. The characteristic reactivity is attributed to both the triangular positioning and varied degrees of oxidation of the under-coordinated Pt at Te vacancies.

Alloying with Mn Enhances the Activity and Durability of the CoPt Catalyst toward the Methanol Oxidation Reaction

To improve the catalytic performance and durability of Pt catalysts used for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), alloying of Pt with other transition metals such as Ru, Co, Ni, and Fe is considered an effective approach. Despite the significant progress made in the preparation of bimetallic alloys and their utilization for MOR, improving the activity and durability of the catalysts to make them commercially viable remains a stiff challenge. In this work, trimetallic Pt_100-x(MnCo)_x (16 < x < 41) catalysts were successfully synthesized via borohydride reduction followed by hydrothermal treatment at 150 °C. The electrocatalytic performance of the synthesized trimetallic Pt_100-x(MnCo)_x (16 < x < 41) catalysts toward MOR was studied using cyclic voltammetry and chronoamperometry. The results affirm that all Pt_100-x(MnCo)_x (16 < x < 41) alloys have superior MOR activity and durability as compared to bimetallic PtCo alloys and commercially available Pt/C (comm. Pt/C) catalysts. Among all the compositions studied, the Pt₆₀Mn_1.7Co_38.3/C catalyst exhibited superior mass activity (1.3 and 1.9 times higher than those of Pt₈₁Co₁₉/C and comm. Pt/C, respectively) toward MOR. Furthermore, all the newly synthesized Pt_100-x(MnCo)_x/C (16 < x < 41) catalysts showed better CO tolerance when compared with comm. Pt/C. This improved performance of the Pt_100-x(MnCo)_x/C (16 < x < 41) catalyst can be attributed to the synergistic effect of Co and Mn on the Pt lattice.

Recent Advances on Transition-Metal-Based Layered Double Hydroxides Nanosheets for Electrocatalytic Energy Conversion

Transition-metal-based layered double hydroxides (TM-LDHs) nanosheets are promising electrocatalysts in the renewable electrochemical energy conversion system, which are regarded as alternatives to noble metal-based materials. In this review, recent advances on effective and facile strategies to rationally design TM-LDHs nanosheets as electrocatalysts, such as increasing the number of active sties, improving the utilization of active sites (atomic-scale catalysts), modulating the electron configurations, and controlling the lattice facets, are summarized and compared. Then, the utilization of these fabricated TM-LDHs nanosheets for oxygen evolution reaction, hydrogen evolution reaction, urea oxidation reaction, nitrogen reduction reaction, small molecule oxidations, and biomass derivatives upgrading is articulated through systematically discussing the corresponding fundamental design principles and reaction mechanism. Finally, the existing challenges in increasing the density of catalytically active sites and future prospects of TM-LDHs nanosheets-based electrocatalysts in each application are also commented.

Understanding Trends in Electrochemical Methanol Oxidation Reaction Activity on a Single Transition-Metal Atom Embedded in N-Coordinated Graphene Catalysts

The lack of efficient catalysts and research on the mechanism for the methanol oxidation reaction (MOR) impedes the development of direct methanol fuel cells. In this work, based on density functional theory calculations, we systematically investigated the activity trends of electrochemical MOR on a single transition-metal atom embedded in N-coordinated graphene (M@N₄C). By calculating the free energy diagrams of MOR on M@N₄C, Co@N₄C was screened out to be the most effective MOR catalyst with a low limiting potential of 0.41 V due to the unique charge transfers and electronic structures. Importantly, one- and two-dimensional volcano relationships in MOR on M@N₄C catalysts are established based on the d-band center and the Gibbs free energy of ΔG*CH3OH and ΔG_*CO, respectively. In one word, this work provides theoretical guides toward the improved activity of MOR on M@N₄C and hints for the design of active and efficient MOR electrocatalysts.

A Direct Catalytic Ethanol Fuel Cell (DCEFC) Modified by LDHs, or by Catalase-LDHs, and Improvement in Its Kinetic Performance: Applications for Human Saliva and Disinfectant Products for COVID-19

In this work, it has been experimentally proven that the kinetic performance of a common Direct Catalytic Ethanol Fuel Cell (DCEFC) can be increased by introducing nanostructured (Zn^II,Al^III(OH)₂)⁺NO₃^-·H₂O Layered Double Hydroxides (LDHs) into the anode compartment. Carrying out the measurements with the open-circuit voltage method and using a kinetic format, it has been shown that the introduction of LDHs in the anodic compartment implies a 1.3-fold increase in the calibration sensitivity of the method. This improvement becomes even greater in the presence of hydrogen peroxide in a solution. Furthermore, we show that the calibration sensitivity increased by 8-times, when the fuel cell is modified by the enzyme catalase, crosslinked on LDHs and in the presence of hydrogen peroxide. The fuel cell, thus modified (with or without enzyme), has been used for analytical applications on real samples, such as biological (human saliva) and hand disinfectant samples, commonly used for the prevention of COVID-19, obtaining very positive results from both analytical and kinetic points of view on ethanol detection. Moreover, if the increase in the calibration sensitivity is of great importance from the point of view of analytical applications, it must be remarked that the increase in the speed of the ethanol oxidation process in the fuel cell can also be extremely useful for the purposes of improving the energy performance of a DCEFC.

High-performance IN738 superalloy derived from turbine blade waste for efficient ethanol, ethylene glycol, and urea electrooxidation

In this work, IN738 superalloy used previously in gas turbines was recycled and used as a working electrode for the electrooxidation of different fuels, namely ethylene glycol, ethanol, and urea. The electrocatalytic efficiency of the electrode was studied by cyclic voltammetry, chronoamperometry, and electrochemical impedance. Several kinetics parameters like diffusion coefficient, Tafel slope, rate constant, and activation energy were calculated. The modified electrode was characterized as received using XRD, SEM, and EDAX to elucidate the crystal structure and surface morphology before and after electrochemical oxidation. The anodic current densities of electrochemical oxidation of ethanol, ethylene glycol, and urea were 29, 17, and 12 mA.cm−2, respectively, in an alkaline solution at a potential of 0.6 V (vs. Ag/AgCl). The kinetic parameters like diffusion coefficients for ethanol, ethylene glycol, and urea were found to be 1.5 $$\times$$ × 10–6, 1.038 $$\times$$ × 10–6, and 0.64 $$\times$$ × 10–6 cm2 s−1, respectively. The charge transfer resistances were estimated for electrooxidation of different fuels by electrochemical impedance spectroscopy (EIS).

Graphical Abstract

A Critical Review on Artificial Intelligence for Fuel Cell Diagnosis

In recent years, fuel cell (FC) technology has seen a promising increase in its proportion in stationary power production. Several pilot projects are in operation across the world, with the number of running hours steadily rising, either as stand-alone units or as part of integrated gas turbine–electric energy plants. FCs are a potential energy source with great efficiency and zero emissions. To ensure the best performance, they normally function within a confined temperature and humidity range; nevertheless, this makes the system difficult to regulate, resulting in defects and hastened deterioration. For diagnosis, there are two primary approaches: restricted input information, which gives an unobtrusive, rapid yet restricted examination, and advanced characterization, which provides a more accurate diagnosis but frequently necessitates invasive or delayed tests. Artificial Intelligence (AI) algorithms have shown considerable promise in providing accurate diagnoses with quick data collecting. This work focuses on software models that allow the user to evaluate many different possibilities in the shortest amount of time and is a vital method for proper and dynamic analysis of such entities. The artificial neural network, genetic algorithm, particle swarm optimization, random forest, support vector machine, and extreme learning machine are common AI approaches discussed in this review. This article examines the modern practice and provides recommendations for future machine learning methodologies in fuel cell diagnostic applications. In this study, these six AI tools are specifically explained with results for a better understanding of the fuel cell diagnosis. The conclusion suggests that these approaches are not only a popular and beneficial tool for simulating the nature of an FC system, but they are also appropriate for optimizing the operational parameters necessary for an ideal FC device. Finally, observations and ideas for future research, enhancements, and investigations are offered.

Theoretical insights into effect of surface composition of Pt-Ru bimetallic catalysts on CH3OH oxidation: mechanistic considerations

A deeper mechanistic understanding on CH₃OH oxidation on Pt-Ru alloys with different Ru surface compositions is provided by DFT-based theoretical studies in this paper. The present results show that alloying and surface compositions of Ru can change CH₃OH oxidation pathway and activity. The optimal surface composition of Ru is speculated to be ca. 50% since the higher Ru surface composition can lead to formation of carbonaceous species that can poison surface. Our present calculated Ru surface composition of ca. 50% exhibits excellent consistency with experimental studies. The origin of enhanced catalytic activity of Pt-Ru alloys is determined. The significantly decreased surface work functions after alloying suggest more electrons are transferred into adsorbates. The calculated lower electrode potentials after alloying imply that lower overpotentials are required for CH₃OH oxidation. The excellent consistency with experimental study on decreased onset potentials after alloying further confirms accuracy of our present calculated results. It is hoped that a systematic understanding of the atomic- and molecular-level processes on CH₃OH oxidation mechanisms on Pt-Ru alloys will result in the ultimate goal of the explanation of origin of enhanced electrocatalytic activity and design of improved Pt-based alloy electrocatalysts for DMFCs.

Electrochemical preparation of monodisperse Pt nanoparticles on a grafted 4-aminothiophenol supporting layer for improving the MOR reaction

The methanol oxidation reaction (MOR) has recently gained a lot of attention due to its application in fuel cells and electrochemical sensors. To enhance the MOR, noble metal nanoparticles should be homogeneously dispersed on the electrode surface with the aid of one suitable support. In this work, 4-aminothiophenol (4-ATP) molecules which contain simultaneously amine and thiol groups were electro-grafted onto the electrode surface to provide anchoring sites, limit aggregation and ensure good dispersion of metal nanoparticles. The results showed a high density of platinum nanoparticles (PtNPs) with an average size of 25 nm on the glassy electrode modified with a 4-ATP supporting layer. Consequently, the MOR was improved by 2.1 times with the aid of the grafted 4-ATP layer. The electrochemical sensor based on PtNPs/4-ATP/GCE is able to detect MeOH in a linear range from 1.26 to 21.42 mM with a detection limit of 1.21 mM.

Self-Supported Defect-Rich Au-Based Nanostructures as Robust Bifunctional Catalysts for the Methanol Oxidation Reaction and Oxygen Reduction Reaction in an Alkaline Medium

Recently, alkaline direct methanol fuel cells have made great progress with the development of alkaline electrocatalysis, and a wide variety of catalysts have been explored for methanol oxidation reaction (MOR)and oxygen reduction reaction (ORR). However, the slow kinetics of the MOR and ORR remain a great challenge. In this paper, self-supported defect-rich AuCu was obtained by a convenient one-pot strategy. Self-supported AuCu presented a branched, porous nanostructure. The nanobranch consisted of several 13 nm skeletons, which connected in the kink of the structure. Different growth directions co-existed at the kink, and the twin boundaries and dislocations as defects were observed. When the Au-based nanostructure functioned as an electrocatalyst, it showed robust MOR and ORR performance. For the MOR, the forward peak current was 2.68 times greater than that of Au/C; for the ORR, the activity was close to that of Pt/C and significantly better than that of Au/C. In addition, it possessed superior electrochemical stability for MOR and ORR. Finally, an in-depth exploration of the impact of surface defects and electrochemical Cu removal on MOR and ORR activity was carried out to explain the MOR and ORR’s catalytic performance.

Promoted activity of annealed Rh nanoclusters on thin films of Al2O3/NiAl(100) in the dehydrogenation of Methanol-d4

Annealed Rh nanoclusters on an ordered thin film of Al2O3/NiAl(100) were shown to exhibit a promoted reactivity toward the decomposition of methanol-d4, under both ultrahigh vacuum and near-ambient-pressure conditions. The Rh clusters were grown with vapor deposition onto the Al2O3/NiAl(100) surface at 300 K and annealed to 700 K. The decomposition of methanol-d4 proceeded only through dehydrogenation, with CO and deuterium as products, on Rh clusters both as prepared and annealed. Nevertheless, the catalytic reactivity of the annealed clusters, measured with the production of either CO or deuterium per surface Rh site from the reaction, became at least 2-3 times that of the as-prepared ones. The promoted reactivity results from an altered support effect associated with an annealing-induced mass transport at the surface. Our results demonstrate a possibility to practically prepare reactive Rh clusters, regardless of the cluster size, that can tolerate an elevated reaction temperature, with no decreased reactivity.

Recent Advances in Carbon Dioxide Conversion: A Circular Bioeconomy Perspective

Managing the concentration of atmospheric CO2 requires a multifaceted engineering strategy, which remains a highly challenging task. Reducing atmospheric CO2 (CO2R) by converting it to value-added chemicals in a carbon neutral footprint manner must be the ultimate goal. The latest progress in CO2R through either abiotic (artificial catalysts) or biotic (natural enzymes) processes is reviewed herein. Abiotic CO2R can be conducted in the aqueous phase that usually leads to the formation of a mixture of CO, formic acid, and hydrogen. By contrast, a wide spectrum of hydrocarbon species is often observed by abiotic CO2R in the gaseous phase. On the other hand, biotic CO2R is often conducted in the aqueous phase and a wide spectrum of value-added chemicals are obtained. Key to the success of the abiotic process is understanding the surface chemistry of catalysts, which significantly governs the reactivity and selectivity of CO2R. However, in biotic CO2R, operation conditions and reactor design are crucial to reaching a neutral carbon footprint. Future research needs to look toward neutral or even negative carbon footprint CO2R processes. Having a deep insight into the scientific and technological aspect of both abiotic and biotic CO2R would advance in designing efficient catalysts and microalgae farming systems. Integrating the abiotic and biotic CO2R such as microbial fuel cells further diversifies the spectrum of CO2R.

Dependence on Size of Supported Rh Nanoclusters in the Dehydrogenation of Methanol-d4 Obstructed by CO

The size effect on the activity of a catalyst has been a focal issue since ideal catalysts were pursued, whereas that on the degradation of a catalyst, by reaction intermediates such as CO, is little discussed. We demonstrate that the dehydrogenation of methanol-d₄ on supported Rh nanoclusters precovered with CO (Rh_-CO clusters) was obstructed, indicated by a decreased production of CO and D₂; the obstructive effect exhibits a remarkable dependence on the cluster size, with a minimum at a cluster diameter near 1.4 nm. The decreased production arose from a decreased reaction probability controlled by the increased activation energy for each dehydrogenation step (including formation of methoxy-d₃), adsorption energies of CO, and repulsion from the CO array on the Rh_-CO surface. The effects of these factors in deactivating the clusters varied separately with the cluster size. Consequently, the size effect on the CO poisoning should be taken into account in engineering the cluster size to optimize the catalytic performance.

Metal-Based Electrocatalysts for Methanol Electro-Oxidation: Progress, Opportunities, and Challenges

Direct methanol fuel cells (DMFCs) are among the most promising portable power supplies because of their unique advantages, including high energy density/mobility of liquid fuels, low working temperature, and low emission of pollutants. Various metal-based anode catalysts have been extensively studied and utilized for the essential methanol oxidation reaction (MOR) due to their superior electrocatalytic performance. At present, especially with the rapid advance of nanotechnology, enormous efforts have been exerted to further enhance the catalytic performance and minimize the use of precious metals. Constructing multicomponent metal-based nanocatalysts with precisely designed structures can achieve this goal by providing highly tunable compositional and structural characteristics, which is promising for the modification and optimization of their related electrochemical properties. The recent advances of metal-based electrocatalytic materials with rationally designed nanostructures and chemistries for MOR in DMFCs are highlighted and summarized herein. The effects of the well-defined nanoarchitectures on the improved electrochemical properties of the catalysts are illustrated. Finally, conclusive perspectives are provided on the opportunities and challenges for further refining the nanostructure of metal-based catalysts and improving electrocatalytic performance, as well as the commercial viability.

Mechanism of methanol synthesis on Ni(110)

Planewave density functional theory (DFT-PW91) calculations are employed to study the methanol synthesis through CO₂ and CO hydrogenation, as well as the two side reactions: the water gas shift (WGS) reaction and the formic acid formation, on Ni(110).

Catalytic H2O2 Activation by a Diiron Complex for Methanol Oxidation

In nature, C-H bond oxidation of CH₄ involves a peroxo intermediate that decays to the high-valent active species of either a "closed" {Fe^IV(μ-O)₂Fe^IV} core or an "open" {Fe^IV(O)(μ-O)Fe^IV(O)} core. To mimic and to obtain more mechanistic insight in this reaction mode, we have investigated the reactivity of the bioinspired diiron complex [(susan){Fe(OH)(μ-O)Fe(OH)}]²⁺ [susan = 4,7-dimethyl-1,1,10,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraazadecane], which catalyzes CH₃OH oxidation with H₂O₂ to HCHO and HCO₂H. The kinetics is faster in the presence of a proton. ¹⁸O-labeling experiments show that the active species, generated by a decay of the initially formed peroxo intermediate [(susan){Fe^III(μ-O)(μ-O₂)Fe^III}]²⁺, contains one reactive oxygen atom from the μ-oxo and another from the μ-peroxo bridge of its peroxo precursor. Considering an Fe^IVFe^IV active species, a "closed" {Fe^IV(μ-O)₂Fe^IV} core explains the observed labeling results, while a scrambling of the terminal and bridging oxo ligands is required to account for an "open" {Fe^IV(O)(μ-O)Fe^IV(O)} core.

Direct Catalytic Fuel Cell Device Coupled to Chemometric Methods to Detect Organic Compounds of Pharmaceutical and Biomedical Interest

Making use of a small direct methanol fuel cell device (DMFC), used as an analytical sensor, chemometric methods, organic compounds very different from one another, can be determined qualitatively and quantitatively. In this research, the following seven different organic compounds of pharmaceutical and biomedical interest, having in common only one –OH group, were considered: chloramphenicol, imipenem, methanol, ethanol, propanol, atropine and cortisone. From a quantitative point of view, the traditional approach, involving the building of individual calibration curves, which allow the quantitative determination of the corresponding organic compounds, even if with different sensitivities, was followed. For the qualitative analysis of each compound, this approach has been much more innovative. In fact, by processing the data from each of the individual response curves, obtained through the fuel cell, using chemometric methods, it is possible to directly identify and recognize each of the seven organic compounds. Since the study is a proof of concept to show the potential of this innovative methodological approach, based on the combination of direct methanol fuel cell with advanced chemometric tools, at this stage, concentration ranges that may not be the ones found in some real situations were investigated. The three methods adopted are all explorative methods with very limited computation costs, which have different characteristics and, therefore, may provide complementary information on the analyzed data. Indeed, while PCA (principal components analysis) provides the most parsimonious summary of the variability observed in the current response matrix, the analysis of the current response behavior was performed by the “slicing” method, in order to transform the current response profiles into numerical matrices, while PARAFAC (Parallel Factor Analysis) allows to obtain a finer deconvolution of the exponential curves. On the other hand, the multiblock nature of “ComDim” (Common Components and Specific Weight Analysis) has been the basis to relate the variability observed in the current response behavior with the parameters of the linear calibrations.

Ternary PtFeCo alloys on graphene with high electrocatalytic activities for methanol oxidation

Ternary PtFeCo alloys as alternatives to conventional Pt electrocatalysts are highly important in the field of the methanol oxidation reaction. In this study, we demonstrate a one-pot two-step reduction method for the synthesis of graphene supported PtFeCo alloy nanocomposites as an integrated binder-free catalyst. The synergistic effect of alloying with Fe and Co as well as graphene decorating contributes to an increase in the utilization of the noble metal, namely, reducing the amount of Pt in the nanocomposites to 7%. After tailoring the elemental composition of the alloys, Pt₅₂Fe₂₉Co₁₉@G-7% exhibits a mass activity/specific activity of 1758.2 mA mg^-1_Pt/3.42 mA cm^-2 that is 3.13/3.45 times that of commercial Pt/C in an acidic medium. Impressively, it showed a superior mass current density of 9356.1 mA mg^-1_Pt at 60 °C which is close to the operating temperature of direct methanol fuel cells. Moreover, the as-obtained Pt₅₂Fe₂₉Co₁₉@G-7% also exhibited excellent CO tolerance and reliable stability compared to commercial Pt/C. The structural characterization further verifies that the surface strain and electronic effect play a critical role in determining the electrocatalytic properties of PtFeCo@G nanocomposites for the methanol oxidation reaction.

A Suitable Immunosensor for Chloramphenicol Determination: Study of Two Different Competitive Formats

Background:

deep analytical study was performed on two different formats based on a “competitive” ELISA-type assay to develop a suitable, sensitive and cheap immune device for chloramphenicol determination that could be advantageously applied to the analysis of real matrices (pharmaceutical, food and environmental).

Methods:

To this purpose peroxidase enzyme as a marker and an amperometric electrode for hydrogen peroxide, as a transducer, were used. Through the first competitive format, chloramphenicol determination was based on the competition between chloramphenicol and conjugated with biotin-avidinperoxidase chloramphenicol, both free in solution, for anti-chloramphenicol immobilized in the membrane, while the second competitive format was based on the competition between free in solution chloramphenicol and immobilized in membrane one, for anti-chloramphenicol biotin-avidin-peroxidase conjugated free in solution.

Results:

The immunosensor was optimized by comparing the two used different “competitive” working formats on the basis of respective Kaff values, that were found to be about 105 and 104 (mol L-1)-1. The developed immune device displayed good selectivity for Chloramphenicol and LOD (limit of detection) was of the order of 10-9 mol L-1. The immunosensor was also used to test the presence of Chloramphenicol in real matrices such as cow milk, river wastewater and pharmaceutical formulations; recovery tests, using the standard addition method, gave satisfactory results.

Conclusion:

The results proved the validity of this immune device based on the competition between chloramphenicol and conjugated chloramphenicol obtained using biotin-avidin-peroxidase format, by which it is possible to carry out the analysis of chloramphenicol in milk and in river waste-waters with a % RSD ≤ 5 and with recovery values between 96% and 103%.

Renewable Energy and EU 2020 Target for Energy Efficiency in the Czech Republic and Slovakia

Our paper focuses on the renewable energy and EU 2020 target for energy efficiency in the Czech Republic and Slovakia. We study the reduction of greenhouse gas (GHG) emissions in these two EU Member States through the prism of the Europe 2020 strategy and the 3 × 20 climate and energy package and economic growth (represented by the Gross Domestic Product (GDP) that allows to measure the national dynamics and provide cross-country comparisons) without attributing specific attention to issues such as the electrification of transport or heating, and thence leaving them outside the scope of this paper. Both Czech Republic and Slovakia are two post-Communist countries that still face the consequences of economic transformation and struggle with the optimal management of natural resources. Both countries encountered profound system transformation after 1989 that are apparent in all three measures of sustainable development used in our study. We show that it is unlikely that the planned increase in renewable energy in the Czech Republic and Slovakia will reach its targets, but they might succeed in reducing their energy consumption and greenhouse gas emissions. Our findings show that the energy intensity of Czech and Slovak economies increased in the early 2000s and then stabilized at a level about twice of the EU average. It appears that this value is likely to remain the same in the forthcoming years. However, implementation of GHG emissions in the Czech Republic and Slovakia may be at risk in case the proper energy policy is not maintained. Moreover, our results show how the increase in the share of renewable energy and improvement in energy efficiency go hand-in-hand with mining and exploiting the energy sources that is notorious for the transition economies. We also demonstrate that a proper energy policy is required for effectively reducing energy consumption and greenhouse gas emissions. There is a need for commitments made by relevant stakeholders and policymakers targeted at achieving sustainable economic growth and energy efficiency. In addition, we demonstrate that there is a need for maintaining a proper balance between economic development and environmental protection, which is a must for the EU sustainable energy development agenda and all its accompanying targets for all its Member States.

Adsorption and reaction of methanol on Fe3O4(001)

The interaction of methanol with iron oxide surfaces is of interest due to its potential in hydrogen storage and from a fundamental perspective as a chemical probe of reactivity. We present here a study examining the adsorption and reaction of methanol on magnetite Fe₃O₄(001) at cryogenic temperatures using a combination of temperature programmed desorption, x-ray photoelectron spectroscopy, and scanning tunneling microscopy. The methanol desorption profile from Fe₃O₄(001) is complex, exhibiting peaks at 140 K, 173 K, 230 K, and 268 K, corresponding to the desorption of intact methanol, as well as peaks at 341 K and 495 K due to the reaction of methoxy intermediates. The saturation of a monolayer of methanol corresponds to ∼5 molecules/unit cell (u.c.), which is slightly higher than the number of surface octahedral iron atoms of 4/u.c. We probe the kinetics and thermodynamics of the desorption of molecular methanol using inversion analysis. The deconvolution of the complex desorption profile into individual peaks allows for calculations of both the desorption energy and the prefactor of each feature. The initial 0.7 methanol/u.c. reacts to form methoxy and hydroxy intermediates at 180 K, which remain on the surface above room temperature after intact methanol has desorbed. The methoxy species react via one of two channels, a recombination reaction with surface hydroxyls to form additional methanol at ∼350 K and a disproportionation reaction to form methanol and formaldehyde at ∼500 K. Only 20% of the methoxy species undergo the disproportionation reaction, with most of them reacting via the 350 K pathway.

Direct Methanol Catalytic Fuel Cell, for Measuring Ethanol Contents in Pharmaceutical Tinctures

Background:

In order to test real direct applicability for analytical purposes, a small and simple direct methanol (or ethanol) catalytic, enzymatic or non-enzymatic fuel cell (DMFC) was used for the analysis of ethanol-based pharmaceutical tinctures; a detailed experimental study was conducted on five different pharmaceutical tinctures available at drugstores.

Results:

The results obtained using both enzymatic and non-enzymatic devices were compared with those obtained by analyzing the same pharmaceutical samples with a conventional catalase biosensor. Finally, the results were compared with the nominal values provided by manufacturing firms.

Conclusion:

The correlations between the different experimental and nominal values considered were good in general or satisfactory and the applied statistical tests (f-test and t-test) were also very comforting. At the end of the study, the use of enzymatic DMFC proved to be better than non- enzymatic DMFC devices, because it requires shorter analysis times.

Shape-controlled synthesis of planar PtPb nanoplates for highly efficient methanol electro-oxidation reaction

In this work, novel insights into the influence of different nanocrystal structures on the electrocatalytic oxidation of methanol are reported. Herein, we have successfully prepared high-yield PtPb nanoplates in the diethylene glycol (DEG) solvent. The as-obtained PtPb nanoplates with a large surface area of the (102) facet show higher MOR activity and superior durability in alkaline electrolyte compared with both zero-dimensional PtPb nanoparticles and commercial Pt/C. Further chronoamperometric (CA) measurements and discrete Fourier transform (DFT) calculations indicate that the PtPb nanoplates possess much better operation durability and CO tolerance due to the negative adsorption energy of the (102) facet.

Investigation of Thermal Stability and Reactivity of Rh Nanoclusters on an Ultrathin Alumina Film

We studied the structural and morphological evolution of Rh clusters on an ordered ultrathin alumina film grown on NiAl(100) in annealing processes, under ultrahigh vacuum conditions and with various surface probe techniques. The Rh clusters, prepared on vapor deposition of Rh onto the alumina film at 300 K, had an fcc phase and grew in the (100) orientation; the annealing altered the cluster structure little—the lattice parameter decreased by a factor <2%—but the cluster morphology significantly. With elevated temperature, small clusters (diameter ≤1.5 nm) decreased little in size; in contrast, large clusters (diameter ≥2.0 nm) varied in a complex manner—their mean diameter decreased to about 1.5 nm on annealing to 450 K, despite their similar height, while it increased to above 2.0 nm at temperature ≥570 K. This atypical decrease in size was governed predominantly by energetics. Such a reduced size enhanced the total surface area as well as the reactivity of the clusters toward methanol decomposition, so increased the production of D2 (H2) and CO from decomposed methanol-d4 (or methanol). The result implies a higher temperature tolerance for Rh clusters on the alumina film and a practical approach to prepare small Rh clusters with high reactivity.

Insights into how the aqueous environment influences the kinetics and mechanisms of heterogeneously-catalyzed COH* and CH3OH* dehydrogenation reactions on Pt(111)

Water influences catalytic reactions in multiple ways, including energetic and mechanistic effects. While simulations have provided significant insight into the roles that H2O molecules play in aqueous-phase heterogeneous catalysis, questions still remain as to the extent to which H2O structures influence catalytic mechanisms. Specifically, influences of the configurational variability in the water structures at the catalyst interface are yet to be understood. Configurational variability is challenging to capture, as it requires multiscale approaches. Herein, we apply a multiscale sampling approach to calculate reaction thermodynamics and kinetics for COH* dehydrogenation to CO* and CH3OH* dehydrogenation to CH2OH* on Pt(111) catalysts under liquid H2O. We explore various pathways for these dehydrogenation reactions that could influence the overall mechanism of methanol decomposition by including participation of H2O structures both energetically and mechanistically. We find that the liquid H2O environment significantly influences the mechanism of COH* dehydrogenation to CO* but leaves the mechanism of CH3OH* dehydrogenation to CH2OH* largely unaltered.

Detection of Fake Alcoholic Beverages Using Electrolyte-Free Nanogap Electrochemical Cells

Because of the similarity of odor, appearance, and chemical structure of methanol and ethanol, measuring the low concentration of methanol in an alcoholic beverage is difficult to perform in a quick, quantitative, and repeatable fashion. However, it is important for people to monitor the content of methanol in a liquor because a high amount of methanol absorbed will result in blindness, coma, and death. In response to this need, we have developed electrolyte-free methanol electrolysis and ethanol electrolysis based on the nanogap electrochemical cells for the methanol and ethanol sensing. Upon applying a voltage, a high electric field across the nanogap cell enhances the solution ionization and the ion transport rate. Moreover, the nanoscale distance between the electrodes provides a shorter path for electrolysis to easily occur. The nanogap electrochemical cells not only make the direct electrolyte-free organic solvent electrolysis possible but also enhance the sensitivity of the chemical of interest in low-concentration solutions without the influence of the added electrolyte. The nanogap electrochemical cells have been demonstrated having high sensitivity to detect 0.15% methanol volume concentration in deionized water solutions without adding any electrolyte, and its ability for the fake alcoholic beverages' detection has successfully demonstrated.

Synthesis of Pt@TiO2 nanocomposite electrocatalysts for enhanced methanol oxidation by hydrophobic nanoreactor templating

In this work Pt@TiO₂ nanocomposite electrocatalysts for methanol oxidation were synthesized using a one-pot process by hydrophobic nanoreactor templating.

Methanol oxidation on the Pt(321) surface: a theoretical approach on the role of surface morphology and surface coverage effects

We investigated methanol oxidation, decomposition and carbonylation reactions on a high indexed Pt(321) surface.

Platinum-Based Catalysts on Various Carbon Supports and Conducting Polymers for Direct Methanol Fuel Cell Applications: a Review

Platinum (Pt)-based nanoparticle metals have received a substantial amount of attention and are the most popular catalysts for direct methanol fuel cell (DMFC). However, the high cost of Pt catalysts, slow kinetic oxidation, and the formation of CO intermediate molecules during the methanol oxidation reaction (MOR) are major challenges associate with single-metal Pt catalysts. Recent studies are focusing on using either Pt alloys, such as Fe, Ni, Co, Rh, Ru, Co, and Sn metals, or carbon support materials to enhance the catalytic performance of Pt. In recent years, Pt and Pt alloy catalysts supported on great potential of carbon materials such as MWCNT, CNF, CNT, CNC, CMS, CNT, CB, and graphene have received remarkable interests due to their significant properties that can contribute to the excellent MOR and DMFC performance. This review paper summaries the development of the above alloys and support materials related to reduce the usage of Pt, improve stability, and better electrocatalytic performance of Pt in DMFC. Finally, discussion of each catalyst and support in terms of morphology, electrocatalytic activity, structural characteristics, and its fuel cell performance are presented.

Direct Methanol (or Ethanol) Fuel Cell as Enzymatic or Non-Enzymatic Device, Used to Check Ethanol in Several Pharmaceutical and Forensic Samples

It was already demonstrated by our research group that a direct catalytic methanol (or ethanol) fuel cell (DMFC) device can be used also for analytical purposes, such as the determination of ethanol content in beverages. In the present research we extended the application to the analysis of several ethanol-based pharmaceutical products, i.e., pharmaceutical tinctures (dyes) and disinfectants. In recent work we have also shown that the use of alcohol dehydrogenase enzyme as a component of the anodic section of a direct catalytic methanol (or ethanol) fuel cell significantly improves the performance of a simple DMFC device, making it more suitable to measure ethanol (or methanol) in real samples by this cell. At the same time, we have also shown that DMFC can respond to certain organic compounds that are more complex than methanol and ethanol and having R(R')CH-OH group in the molecule. Firstly, pharmaceutical dyes were analyzed for their ethanol content using the simple catalytic DMFC device, with good accuracy and precision. The results are illustrated in the present paper. Additionally, a detailed investigation carried out on commercial denatured alcoholic samples evidenced several interferences due to the contained additives. Secondly, we hypothesized that by using the enzymatic fuel cell it would be possible to improve the determination, for instance, of certain antibiotics, such as imipenem, or else carry out determinations of ethanol content in saliva and serum (simulating forensic tests, correlated to drivers "breath test"); even if this has already been hypothesized in previous papers, the present study is the first to perform them experimentally, obtaining satisfactory results. In practice, all of the goals which we proposed were reached, confirming the remarkable opportunities of the enzymatic (or non-enzymatic) DMFC device.

CO2-based hydrogen storage – hydrogen liberation from methanol/water mixtures and from anhydrous methanol

New strategies for the reforming of methanol under mild conditions on the basis of heterogeneous and molecular catalysts have raised the hopes and expectations on this fuel. This contribution will focus on the progress achieved in the production of hydrogen from aqueous and anhydrous methanol with molecular and heterogeneous catalysts. The report entails thermal approaches, as well as light-triggered dehydrogenation reactions. A comparison of the efficiency and mechanistic aspects will be made and principles of catalytic pathways operating in biological systems will be also addressed.