Direct Methanol Research Articles

Machine learning-guided design of direct methanol fuel cells with a platinum group metal-free cathode

Direct methanol fuel cells (DMFCs) offer a promising solution for clean electricity generation, particularly in small electronics and remote auxiliary power units. However, optimizing their efficiency and performance is challenging due to the complex interactions between various factors. Here, we present a novel approach that integrates experiments with machine learning to model and predict the performance of these fuel cells using atomically dispersed platinum group metal (PGM)-free catalysts at the cathode. Our machine learning models, trained on diverse input parameters, allow for the comprehensive optimization of DMFC performance prior to fabrication and testing. Through extensive experimental validation, we demonstrate that this data-driven approach accurately predicts key performance metrics, such as maximum power output and polarization curves. By combining our models with interpretable game-theory methods, we provide deep insights into the factors governing fuel cell performance, ultimately paving the way for the design of scalable and efficient DMFC technologies.

Black phosphorus nanodots-modified Pt/C electrocatalyst for methanol-tolerant oxygen reduction in direct methanol fuel cells

Black phosphorus nanodots-modified Pt/C electrocatalyst for methanol-tolerant oxygen reduction in direct methanol fuel cells

The key role of the second material's OER activity on MOR durability enhancement of the Pt alloys

Pt-based precious metal catalysts are generally regarded as the best catalyst materials for direct methanol fuel cells due to their high inherent methanol oxidation (MOR) activity. However, the commercial application of Pt catalyst is still facing with severe durability problem. The CO formed by the incomplete oxidation of methanol will occupy the Pt active site, hindering the further progress of the MOR reaction and causing the rapid attenuation of the activity. In this work, a MOR durability enhancement strategy that relation to the OER performance of the second materials M (M=Ni, Co, Fe and Cu) is reported. The precise electrochemical test results showed that the MOR durability of Pt-M alloy changes with the second material, which is related to the OER activity of M materials. The smaller the overpotential and tafel slopes of the M material, the better the MOR durability. Via M material screening, the Co element with the lowest OER overpotential among M promoted the Pt-Co alloy material with the highest MOR durability, resulting an excellent durability sustain 7000 times CV cycles with just 0.53 A mg−1Pt mass activity loss. According to the current generally accepted OER and MOR reaction mechanism, the association of MOR durability with OER activity is most likely derived from the same reaction step of M-OH formation, which played a key role on both reaction. This relationship between OER overpotential and MOR durability helps to screen the second material from the perspective of OER activity to improve the MOR durability of Pt catalysts, which is of great significance for the development of Pt-based CO-resistant MOR catalysts.

Cathodic corrosion induced selective nano-crystallization of Nickel oxo/hydroxo complex on (NiFeCr)SiB amorphous ribbon for alkaline oxygen evolution reaction and methanol oxidation reaction

The study focuses on the development and optimization of (Ni87Fe4Cr9)78Si8B14 amorphous ribbons as self-supported electro-catalysts for oxygen evolution reaction (OER) and methanol oxidation reaction (MOR). Electro-catalytically active nano α-Ni(OH)2 phase (5–10nm) was generated in the amorphous ribbon surface through potentiostatic cathodic corrosion for different time intervals (0–120 min). The X-ray diffraction and scanning electron microscopy results shows the favourable occurrence of dense nanocrystallization of α-Ni(OH)2 between 45 and 90 min of corrosion time. For OER in 1 M KOH, the 60-min surface modified ribbon exhibits an overpotential of 295 mV at 10 mA/cm2 current density and tafel slope of 51 mV dec−1. In case of MOR in 1 M KOH +1 M MeOH, the 90-min corroded ribbon shows lowest potential of 1.38 V vs RHE, at 10 mA/cm2 and tafel slope of 34 mV dec−1. In addition to superior electro-catalytic activity, the optimal surface-modified ribbons show superior long-term stability for OER and MOR studies, indicating its potential application in hydrogen generation and direct methanol fuel cell.

Fabrication and electrochemical investigations of nanostructured PtSn-NiTiO3 heterostructured electrocatalysts for direct methanol oxidation

The methanol oxidation reaction of a PtSn nanoparticle decorated NiTiO3 nanostructured material system is reported in this paper. NiTiO3 and PtSn nanoparticles were formed in rhombohedral and cubic phases, respectively. The crystallite size of the PtSn nanoparticles was calculated to be 2.8 nm from the XRD peak parameters and TEM studies. The surface plasmon resonance peak observed at 308 nm indicates the decoration of PtSn-NiTiO3 nanostructures with Pt nanoparticles on the surface. The chemical oxidation states investigated by XPS showed a metallic state of Pt and Sn with a small amount of surface oxidization. From the electrochemical analysis, the Pt0.5Sn0.5-NiTiO3 nanostructures showed superior electrocatalytic performance with higher electrochemical surface area (252 m2/g), high current density (196 mA/cm2), lower Tafel value (161.31 mV/dec) and small charge transfer resistance. This work demonstrated that the Pt0.5Sn0.5 −NiTiO3 nanostructure would be a suitable electrocatalyst for oxidation for methanol in DMFC.

Layered double hydroxides-derived CoNi alloy nanoparticles encapsulated by porous N-doped carbon nanofibers as efficient methanol electrocatalysts for alkaline direct methanol fuel cells

The exploration of inexpensive electrocatalysts possessing high activity and increased stability to replace precious metal catalysts in the methanol oxidation reaction (MOR) is highly desirable for alkaline direct methanol fuel cells (ADMFCs). This study presents a novel approach to synthesize layered double hydroxides (LDHs)-derived CoNi alloy nanoparticles confined within porous N-doped carbon nanofibers (CoNi@NCNFs) via facile electrospinning and pyrolysis for methanol electrooxidation.The one-dimensional N-doped carbon nanofibers could effectively prevent nanoparticle agglomeration during the pyrolysis of LDH precursors. The optimized CoNi@NCNF3-900 composite exhibits exceptional catalytic activity (80.3mAcm−2) for MOR in alkaline solution, attributed to its hierarchical porous structure, high surface area, and abundant accessible active sites. Furthermore, the catalyst demonstrates competitive electrocatalytic stability, retaining over 90% of its initial current density after 1000 consecutive cyclic voltammetry (CV) cycles. Notably, a single-cell ADMFC assembled with CoNi@NCNF3-900 as the anode catalyst achieves a promising maximum power density of 29.5mWcm−2, highlighting the potential of CoNi@NCNF3-900 for application in DMFC technology and clean energy sources.

Pt Nanoparticles on Multi-Walled Carbon Nanotubes with High CO Tolerance for Methanol Electrooxidation.

Anode catalysts are important for direct methanol fuel cells (DMFCs) of energy conversion. Herein, we report a novel strategy by ethylene glycol-based deep eutectic solvents (EG-DESs) for the fabrication of a multi-walled carbon nanotubes (MWCNTs)-supported Pt nanoparticles catalyst (referred to as Pt/CNTs-EG-DES). The Pt/CNTs-EG-DES catalyst provides an increased electrochemically active surface area (ECSA) and shows remarkably improved electrocatalytic performance towards methanol oxidation reaction compared to Pt/CNTs-W (fabricated in water) and commercial Pt/C catalysts. The improved performance is attributed to the generation of more Pt-O bonds which change the electronic states of the Pt atoms and the special node structure that obtains more active sites for a high CO resistance. This study suggests an effective synthesis strategy for Pt-based electrocatalysts with high performance for DMFC applications.

Recent Progresses and Challenges to Determine Properties of Sulfonated Polyether Ether Ketone Based Electrolytes for Direct Methanol Fuel Cell Applications

AbstractThis review focuses on fillers, modifications, and methods used in the preparation and development of sulfonated poly(ether ether ketone) (sPEEK) membranes, specifically for direct methanol fuel cell (DMFC) applications as proton exchange membranes in recent years. The primary objective is to evaluate recent advancements by emphasizing key characteristics such as water uptake and swelling capacity, ionic conductivity, methanol permeability, and single cell polarization tests. Additionally, the review aims to provide insights for future researchers by discussing the preparation processes of electrolytes. It presents basic characterizations of membrane electrolytes, including evaluations of the sulfonation degree and ion exchange capacities of sPEEK. High performance of membrane electrolytes is essential for commercialization and to compete with established membranes like Nafion®, which has a perfluorosulfonic acid structure. Therefore, the review also covers detailed characterization methods for assessing long‐term stability when available in the related studies. Numerical results and indicators are categorized and tabulated for easy interpretation and comparative analysis.

Palladium nanocrystals immobilized on boron and nitrogen codoped mesoporous carbon spheres as efficient methanol oxidation electrocatalysts

The development of cost-effective and high-performance electrocatalysts is crucial for the widespread application of direct methanol fuel cell. Herein, a convenient and robust method is developed to the controllable fabrication of Pd nanocrystals in situ immobilized on boron and nitrogen codoped mesoporous carbon spheres (Pd/BNMCS) as anode catalysts for the methanol oxidation reaction. The as-derived Pd/BNMCS hybrids are equipped with a series of useful structural features, such as large specific surface area, abundant mesoporous channels, presence of plentiful B and N atoms, well-dispersive Pd nanoparticles, and good electrical conductivity. As a consequence, the optimized Pd/BNMCS catalyst demonstrates superior electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area, high mass/specific activities, and reliable long-term stability, which are significantly better than those of traditional carbon black and undoped mesoporous carbon sphere supported Pd catalysts. This study highlights the potential of heteroatom codoped mesoporous carbon matrixes in the construction of advanced noble metal electrocatalysts for practical fuel cell applications.

The Effect of a Reduction in the Catalyst Loading on a Mini Passive Direct Methanol Fuel Cell

Mini passive direct methanol fuel cells (mpDMFCs) appear to be a promising alternative for powering portable devices, since they use a liquid fuel, have a fast refuelling time, have a high efficiency and have a low environmental impact. However, some issues need to be solved before their commercialization, such as methanol crossover, short lifetime and high costs. The present work studies the effect of reducing the anode and cathode catalyst loading on the performance of a mpDMFC towards a reduction in the system costs and the characterization of the system losses. The undesirable losses that affect the fuel cell performance were identified and quantified using the electrochemical impedance spectroscopy (EIS) technique. Accordingly, a novel equivalent electric circuit (EEC) was proposed, accurately reproducing the mini pDMFC. In this work, a maximum power density of 7.07 mW cm−2 was obtained, with a methanol concentration of 5 M, using 2 mg cm−2 Pt-RuB and 4 mg cm−2 PtB. The mpDMFC allowed the cell to work with high methanol concentrations and reduced anode catalyst loadings.

Recycling of spent heat pack towards Fe-Fe3O4@NC catalyst for ORR in direct methanol fuel cells and Al-air batteries

The effective repurposing of waste materials is crucial for sustainable development. The widespread use of disposable iron-based chemical warmers (IBCW) generates substantial solid waste annually. In this study, IBCWs were repurposed as raw materials to synthesize different electrocatalyst composites comprising metallic and oxide forms of iron embedded in nitrogen-doped carbon (NC). The composites were evaluated as oxygen reduction reaction (ORR) catalysts. The optimized Fe-Fe3O4@NC demonstrated enhanced ORR kinetics, with an onset potential of 0.92 V and a half-wave potential of 0.86 V vs. RHE. As an air cathode for direct methanol fuel cell (DMFC), Fe-Fe3O4@NC achieved a power density of 33.3 mW cm−2 at 88 mA cm−2, demonstrating its practical applicability. Additionally, a quasi solid-state aluminium-air battery (SAAB) was assembled using this catalyst as the air cathode with a PVA-KOH gel electrolyte and the separator. The quasi SAAB exhibited an open circuit voltage (OCV) of 1.46 V, a power density of 40 mW cm-2, and good rate capability compared to Pt/C. The combined effect of metallic and oxide iron with nitrogen doping enhances the overall catalytic activity. This study demonstrates that IBCWs can be effectively transformed into valuable catalysts for renewable energy applications, enabling clean and sustainable utilization of waste materials.

Ni- and Co-Based MOF-Derived NixCo3-xO4 Materials: As an Efficient Anode for Direct Methanol Fuel Cell Application.

Finding inexpensive and efficient anode materials is crucial for the oxidation of methanol in the direct methanol fuel cell (DMFC), which is the key electrode reaction. Herein, we report metal-organic framework (MOF)-derived Co3O4, NiO, and NixCo3-xO4 (where x = 1.5, 1, and 0.6) materials deposited on nickel foam as efficient anode material for methanol oxidation. Among them, NiCo2O4 exhibited the highest methanol oxidation activity, owing to its lowest charge-transfer resistance (0.097 Ω) and high electrochemically active surface area (1950 cm2), resulting in the lowest onset potential of 0.35 V vs Hg/HgO. The optimized Ni-to-Co ratio and synergistic effect between Ni and Co metals enable NiCo2O4 to achieve the highest mass activity of 151 mA mg-1 and geometric current density of 288 mA cm-2, demonstrating excellent durability over 14 h at 0.6 V. In addition, to optimize methanol concentration, all the electrocatalysts were tested in a range of methanol concentrations, showing 0.5 M methanol as the optimal concentration. This study focuses on optimizing the metal ratio and methanol concentration to achieve the highest catalytic activity. Additionally, this lays the foundation for developing diverse MOF-derived electrocatalysts and advancing DMFCs.

Metal-organic framework-derived nanoflower and nanoflake metal oxides as electrocatalysts for methanol oxidation.

The energy crisis is the most urgent issue facing contemporary society and needs to be given top priority. As energy consumption rises, environmental pollution is becoming a serious issue. Direct methanol fuel cells (DMFCs) have emerged as the most promising energy source for a variety of applications such as electric vehicles and portable devices. Unfortunately, the kinetics of methanol oxidation is slow and needs an electrocatalyst to improve the reaction kinetics and the overall fuel cell efficiency. Herein, a straightforward hydrothermal procedure was utilized to prepare copper, nickel, and cobalt-based MOF composites by altering the elemental molar ratios. Cu-MOF (MOFP1), Cu/Ni-MOF (MOFP2), and Cu/Ni/Co-MOF (MOFP3) were prepared after carbonization and characterized using several key techniques such as FTIR, XRD, SEM, and EDX. The SEM analysis reveals that the morphology of MOFP1 is spherical aggregated particles, while that of MOFP2 or MOFP3 is in the form of nanoflakes and nanoflowers. Moreover, upon application of these composites as electrocatalysts for methanol electro-oxidation in an alkaline medium of 1 M NaOH using cyclic voltammetry (CV) and chronoamperometry (CA) tests, the electrochemical performance of MOFP2 in 1 M methanol exhibits the best performance for methanol oxidation with a current density reaching 38.77 mA cm-2 at a scan rate of 60 mV s-1. This can be attributed to the unique porous open flower structure and the synergistic effect between copper, nickel, and 2-aminoterephthalic acid which develop its catalytic activity.

Optimizing Activity and Stability in AgCl‐CuO Electrocatalysts: Insights from Different Morphologies for Enhanced ORR Performance

Highly enduring and methanol‐tolerant electrocatalysts are pertinent to revolutionizing direct methanol fuel cell (DMFC) technologies. Transition metal‐based electrocatalysts are anticipated to rank among the remarkable electrocatalysts for boosting the sluggish Oxygen Reduction Reaction (ORR) kinetics. Herein, we report a facile approach to optimize the activity and stability of the AgCl‐CuO systems. The tailored Nano Particle‐Nano Rod (NP‐NR) and Nano Leaf (NL) like morphologies deliver remarkable bifunctional catalytic performance for oxygen reduction and hydrogen evolution reactions, sustained activity, and comparatively better stability for ORR. A meager shift of only 0.014 V and 0.024 V in the half‐wave potential is observed in the NP‐NR and NL structures, respectively, for the ORR even after 2500 cycles. Furthermore, both the AgCl‐CuO composite exhibits an excellent tolerance to methanol.

Facile synthesis of green graphite-based (Ni/Cu/N) MOF composite for a methanol oxidation reaction

Recently, direct methanol fuel cells (DMFCs) have been regarded as the greatest energy-producing owing to their low operating temperature, high production rate of methanol, and low greenhouse gas emission. However, the energy conversion efficiency of the DMFCs is still unsatisfactory due to the slow kinetics of the fuel oxidation reaction. So, an economic electrocatalyst with high efficiency and good stability is still needed. Herein, low-cost nanocomposites of (Ni/Cu/N) MOF and palm pollen-derived G-graphite were prepared with different ratios namely, (1:1), (1:2), and (2:1) through a solvothermal reaction. The nanocomposites were characterized via X-ray diffraction (XRD), Scanning electron Microscopy (SEM), Fourier transform infrared (FTIR), Thermal gravimetric analysis (TGA), and, (Brunauer–Emmett–Teller) technique (BET). Electrodes have been tested as electro-catalysts for methanol-oxidation reaction (MOR) in a basic medium. As revealed from the cyclic voltammetry measurements, all electrodes exhibit a good response to MOR, being the nanocomposite with the ratio between (Ni/Cu/N) MOF and G-graphite (2:1) is the best with an oxidation peak current density of 55 mA/cm2 at a scan rate of 50 mV/s, with an onset potential of 0.35 V, and stability reaches 96 %. The electrochemical impedance spectroscopy (EIS) test showed that the ratio (2:1) has the lowest charge transfer resistance, RCT, of 5.21 Ω which confirms its higher electrochemical activity. This superior performance of the (Ni/Cu/N) MOF and G-graphite (2:1) over other reported MOF-based electrocatalysts is attributed to the synergistic effect of the (Ni/Cu/N) MOF electrocatalyst, wherein Ni and Cu provide redox electrocatalytic active sites for MOR while the G-graphite contributes towards the chemical stability and electrical conductivity of the electrode, respectively. The good activity and stability of the prepared electrodes suggest the potential use of these electrodes as electrocatalysts for MOR in direct methanol fuel cells (DMFCs).This study opens the venue for valorizing the natural wastes derived graphitic material as stable supporting material in Mof based composites electrodes for MOR.

N-doped titanium oxide/carbon composite as supports for platinum catalysts in highly efficient methanol oxidation

The commercialization of direct methanol fuel cells (DMFCs) faces significant challenges due to the susceptibility of conventional platinum-based catalysts to poisoning by intermediates such as CO and HCOO− generated during the methanol oxidation reaction (MOR). This study details the synthesis of a highly porous titanium dioxide/carbon composite (TCC) using NH2-MIL-125(Ti) (MIL = Matérial Institut Lavoisier) as a precursor. To enhance the conductivity and catalytic properties of TCC, a nitriding reaction is conducted in an NH3 atmosphere, producing a nitrogen-doped titanium oxide/carbon composite (N-TCC). The resulting N-TCC is employed as a support for a platinum catalyst to improve MOR performance in DMFCs. The Pt/N-TCC catalyst demonstrates high catalytic performance, achieving a mass activity of 537 mA mg−1 for the MOR, marking a 39 % increase over the commercial Pt/C catalyst. Furthermore, the Pt/N-TCC catalyst exhibits a low onset potential for CO oxidation, a higher If/Ib ratio, and greater stability in chronoamperometry test, indicating high resistance to CO poisoning and enhanced chemical stability. Therefore, N-TCC can be used as a promising support for Pt-based catalysts in DMFC applications.

Integrating Hydrogenated TiO2-Modified Carbon-Supported PtRu Anodes and Fe–N–C Cathodes for High-Performance Direct Methanol Fuel Cells

Integrating Hydrogenated TiO₂-Modified Carbon-Supported PtRu Anodes and Fe–N–C Cathodes for High-Performance Direct Methanol Fuel Cells

Real-time power optimization based on Q-learning algorithm for direct methanol fuel cell system

Efficient real-time power optimization of direct methanol fuel cell (DMFC) system is crucial for enhancing its performance and reliability. The power of DMFC system is mainly affected by stack temperature and circulating methanol concentration. However, the methanol concentration cannot be directly measured using reliable sensors, which poses a challenge for the real-time power optimization. To address this issue, this paper investigates the operating mechanism of DMFC system and establishes a system power model. Based on the established model, reinforcement learning using Q-learning algorithm is proposed to control methanol supply to optimize DMFC system power under varying operating conditions. This algorithm is simple, easy to implement, and does not rely on methanol concentration measurements. To validate the effectiveness of the proposed algorithm, simulation comparisons between the proposed method and the traditional perturbation and observation (P&O) algorithm are implemented under different operating conditions. The results show that proposed power optimization based on Q-learning algorithm improves net power by 1% and eliminates the fluctuation of methanol supply caused by P&O. For practical implementation considerations and real-time requirements of the algorithm, hardware-in-the-loop (HIL) experiments are conducted. The experiment results demonstrate that the proposed methods optimize net power under different operating conditions. Additionally, in terms of model accuracy, the experimental results are well matched with the simulation. Moreover, under varying load condition, compared with P&O, proposed power optimization based on Q-learning algorithm reduces root mean square error (RMSE) from 7.271% to 2.996% and mean absolute error (MAE) from 5.036% to 0.331%.

Molten salt approach of zeolitic imidazole framework derived strontium doped porous carbon based bifunctional electrocatalysts for direct methanol fuel cell

Direct Methanol Fuel Cells (DMFCs) have sparked widespread interest and offer a viable approach for generating power. It has a number of commercial advantages, including low price, compact construction, and a quick refilling process that directly convert the chemical energy of methanol into electrical energy through an electrochemical reaction. However, direct methanol fuel cells (DMFCs) frequently rely on platinum catalysts, which are expensive and limited in scalability. Platinum catalysts can be poisoned by carbon monoxide (CO) thus preventing their widespread commercialization. Due to these drawbacks, there is growing interest in developing catalysts based on non-noble metals to improve DMFC technology's deployment. Herein, we report a facile synthesis method using a molten salt approach, which involves the solvent-free mixing of strontium nitrate tetrahydrate with ZIF-67, followed by direct pyrolysis in an Ar/H2 atmosphere at 800 °C. For methanol oxidation the strontium oxide loaded catalytic materials i.e., CoxOy SrO/C (1:1) exhibited a peak current density of 161 mA/cm2 and stability of 71 % over 28800s and for ORR it exhibit current density of −5.86 mA/cm2 and half wave potential of 0.87 V. The facile MOF synthesis strategy, enhanced by molten salt processing, shows great potential for creating non-noble catalytic materials for high-performance fuel cells.

Vapor-feed direct methanol fuel cells using pure methanol

This work optimizes the performance of the direct methanol fuel cell (DMFC) to increase its efficiency and strengthen its validity in portable power generation. Specifically, this work focuses on optimizing vapor-feed supply techniques and incorporating water management layers (WMLs) to analyze their effect on methanol crossover. The significance of the vapor-feed supply technique is to enhance the reaction kinetics of the methanol oxidation reaction (MOR) and enable the use of pure methanol (MeOH) as a fuel. Pure methanol is the ideal fuel for the DMFC as it has the highest possible energy density compared to dilute concentrations. However, use of pure methanol is hindered by methanol crossover, which is regarded as the largest technical barrier to commercializing DMFCs. This study measured methanol crossover through a CO2 sensor attached to the cathode outlet and added hydrophobic WMLs to the cathode to alleviate the methanol crossover. The hydrophobic WMLs increased the mass transfer resistance to generate a pressure gradient that encourages water backflow for use in both the proton exchange membrane (PEM) and anode reactions. The influence of vapor flow rate and fuel concentration will also be explored to show their impact on performance and methanol crossover. Likewise, long-term consumption and durability tests were conducted with and without a WML to dictate the WML’s superior fuel efficiency, total efficiency, energy density, and reduced methanol crossover using pure methanol. The addition of the WML increased the energy density of the vapor feed DMFC, using pure methanol, from 705.9 Wh kgMeOH-1 to 867.7 Wh kgMeOH-1 and lowered the crossover current density by 14.8 % when discharged at a constant 200 mA cm−2.