High Peak Current Density Research Articles

Bimetallic Rh–Pd aerogels as efficient materials for ethanol electrooxidation

This study introduces a series of Rh–Pd bimetallic aerogels Rh75Pd25, Rh50Pd50, and Rh25Pd75 as efficient electrocatalysts for ethanol electrooxidation, crucial for direct ethanol fuel cell technology. The bimetallic Rh–Pd and monometallic Rh and Pd aerogels were synthesized from RhCl3 and PdCl2 as starting materials and sodium borohydride as the reducing agent. A combination of X-ray photoelectron spectroscopy, elemental mapping, and electron microscopy studies of the bimetallic aerogels enable compositional analysis of the materials and provide insight into the porous 3D nanoarchitecture. Importantly, the material performs efficiently as an electrocatalyst on glassy carbon electrodes for the oxidation of ethanol under basic conditions (1.0 M KOH) at onset potentials ranging from −0.59 to −0.64 V (vs. Hg/HgO). Importantly, these materials exhibit high peak current densities of 216 mA/cm2 for the Rh-rich Rh75Pd25 to 536 mA/cm2 for Rh25Pd75, which are significantly higher than reported peak current densities for other Pd-containing electrocatalysts. The 1H and 13C NMR techniques were used to evaluate products for ethanol electrooxidation, with the results indicating selectivity for acetic acid. This demonstrates an enhanced catalytic activity, selectivity to acetic acid vs. CO2, representing a significant step in advancing DEFCs and their broader application in sustainable energy technologies.

Effective Non-Precious Metal Oxide Supported Carbon as a High Performance Bifunctional Electrocatalyst for All Vanadium Redox Flow Batteries

As one of the most promising electrochemical energy storage systems, vanadium redox flow batteries (VRFBs) have received increasing attention owing to their attractive features for large-scale storage applications. However, their high production cost and relatively low energy efficiency still limit their feasibility. One of the critical components of VRFBs that can significantly influence the effectiveness and final cost is the electrode. Therefore, the development of an ideal electrocatalyst with low cost, large active surface area, good chemical stability, and excellent electrochemical activity toward the VO2+/VO2 + and V2+/V3+ redox reactions is essential for the design of VRFBs. Hence, we prepared a stable, high catalytic activity and uniformly distributed non-precious metal oxide nanoparticles on the surface graphene sheets via two step routes, hydrothermal followed by annealing at optimum temperature for VRFB applications. Among the samples, the prepared electrocatalyst shows the best electrochemical activity with lowest peak potential separation and highest peak current density toward VO2 +/VO2+ and V2+/V3+ redox reactions. This observation is due to the synergistic effects related to the presence of excess oxygen vacancies on the metal oxide, the high content of oxygen functional groups, and the high electrical conductivity of the graphene sheets. Hence, the prepared electrocatalyst grown on the surface of graphite felt (GF) support demonstrates the optimal electrochemical activity with the energy and voltage efficiencies of 76.8% and 80.9%, respectively, which are much greater than those of the 59.8% and 63.2% attained from pristine GF at 100 mA cm–2. Moreover, the electrode presented good stability and durability in acidic electrolyte during long-term operations for 100 cycles at a higher current density of 100 mA cm–2.

Aqueous Synthesis of Au10Pt1 Nanorods Decorated with MnO2 Nanosheets for the Enhanced Electrocatalytic Oxidation of Methanol.

Developing novel catalysts with high activity and high stability for the methanol oxidation reaction (MOR) is of great importance for the ever-broader applications of methanol fuel cells. Herein, we present a facile technique for synthesizing Au10Pt1@MnO2 catalysts using a wet chemical method and investigate their catalytic performance for the MOR. Notably, the Au10Pt1@MnO2-M composite demonstrated a significantly high peak mass activity of 15.52 A mg(Pt)-1, which is 35.3, 57.5, and 21.9 times greater than those of the Pt/C (0.44 A mg(Pt)-1), Pd/C (0.27 A mg(Pt)-1), and Au10Pt1 (0.71 A mg(Pt)-1) catalysts, respectively. Comparative analysis with commercial Pt/C and Pd/C catalysts, as well as Au10Pt1 HSNRs, revealed that the Au10Pt1@MnO2-M composite exhibited the lowest initial potential, the highest peak current density, and superior CO anti-poisoning capability. The results demonstrate that the introduction of MnO2 nanosheets, with excellent oxidation capability, not only significantly increases the reactive sites, but also promotes the reaction kinetics of the catalyst. Furthermore, the high surface area of the MnO2 nanosheets facilitates charge transfer and induces modifications in the electronic structure of the composite. This research provides a straightforward and effective strategy for the design of efficient electrocatalytic nanostructures for MOR applications.

High-performance negative differential resistance characteristics in homoepitaxial AlN/GaN double-barrier resonant tunneling diodes

In this work, high-performance negative differential resistance (NDR) characteristics are demonstrated in homoepitaxial AlN/GaN double-barrier resonant tunneling diodes (RTDs). The devices are grown by plasma-assisted MBE on bulk GaN substrates and exhibit robust and repeatable NDR at RT. A high peak current density of 183 kA cm−2 is simultaneously demonstrated with a large peak-to-valley current ratio of 2.07, mainly benefiting from the significantly reduced dislocation density and improved hyper-abrupt heterointerfaces in the active region, which boosts the electron quantum transport in the resonant tunneling cavity. The achievement shows the promising potential to enhance the oscillation frequency and output power of GaN-based RTD oscillators, imperative for next-generation high-power solid-state compact terahertz oscillators application.

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.

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.

Controlled Synthesis of Bead‐like Pt as an Efficient Electrocatalyst for Electrocatalytic Ammonia Oxidation

AbstractPromoting electrocatalytic ammonia oxidation reaction (AOR) holds the key to develop efficient direct ammonia fuel cells (DAFCs) and ammonia‐mediated hydrogen production (AMHP). Recent investigations indicated that Pt with the exposure of (100) facet has a moderate *N intermediate bonding strength, resulting in the highest AOR electrocatalytic activity among others. Therefore, maximizing the exposure of (100) planes with high active surface area is highly desired for efficient electrocatalysts. In this paper, Pt catalyst composed of directional alignment of nanoparticles around 50 nm (Pt‐100/C) were synthesized by hydrothermal method in the presence of KOH. The KOH concentration was found to modulate the one‐dimensional alignment of nanoparticles. The electrocatalyst showed the largest electrochemically active areas and the highest peak current density (3.14 mA cm−2), and the catalyst exhibited high stability after 500 cycles. A series of electrochemical tests and structural characterizations show that unique bead‐structured Pt combines the excellent activity of nanoparticles with the structural stability of nanowires. A scheme for “exchanging electrodes” has been proposed to solve the problem of catalyst poisoning caused by AOR in AMHP.

Cross-dimensional multi-physics model and two-phase mass-transport enhancement for the hydrogen peroxide-based fuel cell

The direct liquid fuel cell utilizing hydrogen peroxide as an oxidant is considered to be the promising energy conversion technology, owing to its superior energy density and theoretical voltage. In the hydrogen peroxide-based fuel cells, the ever-changing two-phase mass transport and multi-component reaction processes resulting from the hydrogen peroxide self-decomposition exerts a pivotal influence on their performance. In this work, taken hydrogen peroxide self-decomposition into account, a cross-dimensional multi-physics model for the hydrogen peroxide-based fuel cell was proposed and developed to clarify the complex mechanisms of transports and reactions. In this ingeniously developed model, the multi-component reaction in the porous electrode is elucidated by a two-dimensional (2D) sub-model, the two-phase mass transport in the flow field is captured by a three-dimensional (3D) sub-model, and the one-dimensional (1D) correlation equation is served as a bridge between them. The uneven distribution of gas–liquid volume, velocity and current density and their relationships in fuel cell with serpentine flow field and dot matrix flow field were thus achieved. Furthermore, a novel gradient dot matrix flow field was developed to match the two-phase mass transport and multi-component reaction processes of hydrogen peroxide-based fuel cell. It is found that the continuously increasing pressure and velocity along flow path is balanced by the gradient-downsized ribs and the formation of large-volume oxygen bubbles is prevented by the gradient-densified ribs, achieving obviously uniformized current density distribution. Moreover, the gradient dot matrix flow field enables 54 % higher average hydrogen peroxide coverage contents (49 %) and 86 % lower average pressure drop (172 Pa) compared to the serpentine flow field, yielding 6.3 % higher peak power density (210 mW cm−2) and ultra-low extra pump power in fuel cell. This work will make contribution towards gaining profound insights into the intricate mechanisms underlying mass and charge transport, and offering invaluable guidance for the flow field design for the hydrogen peroxide-based fuel cells.

Bio-extract mediated green synthesis of bi-functional ammonium cobalt phosphate nanoflakes electrode/catalyst for supercapattery and ethanol oxidation

The present study proposes a low-cost, green technique to the synthesis of bi-functional ammonium cobalt phosphate for energy storage and conversion applications. The comprehensive physiochemical investigations are carried out using various spectral-analytical techniques. The results of phase and surface morphology confirm the formation of an orthorhombic crystal structure with flakes-like microstructure. With a maximal specific capacity of 448.3 mAhg−1 at 2 mAcm−2, bio-solvent driven NH4CoPO4·H2O with graphene oxide (GO) nanoflakes demonstrates exceptional battery-type energy storage capabilities. As constructed supercapattery device exhibits a high specific energy of 85.4 Wh kg−1 at power output of 1283 W kg−1 and 81 % stability after 5000 cycles. Further exploration as a non-precious metal-based catalyst for ethanol oxidation reaction (EOR), NH4CoPO4·H2O /GO showed a high peak current density of 83.4 mAcm−2 at 20 mVs−1. Coupled oxygen/hydrogen evolution processes are investigated in 1 M KOH in order to acquire a better understanding of the catalyst's EOR activity. The NH4CoPO4·H2O/GO sample exhibited the lowest overpotentials of |ηOER@10| = 420 mV, and |ηHER@10| = 112 mV, with Tafel slopes of 169.8 mV dec−1 for OER and 132.8 mV dec-1 for HER, respectively. This is due to the catalyst's slow OH adsorption during OER and the limited H*recombination during HER. Therefore, this approach provides a green and cost-effective method to synthesis efficient bi-functional electrode/catalysts for supercapattery and alkaline fuel cells.

Hole-tunneling Si0.82Ge0.18/Si triple-barrier resonant tunneling diodes with high peak current of 297 kA/cm2 fabricated by sputter epitaxy

Hole-tunneling Si0.82Ge0.18/Si asymmetric triple-barrier (TB) resonant tunneling diodes (p-RTDs) were created by sputter epitaxy instead of conventional chemical vapor phase epitaxy. As a result, a peak current density (PCD) of 297 kA/cm2 with a peak-to-valley current ratio of 7.3 was recorded at room temperature. The observed high planarity of the films grown by sputter epitaxy is also considered one of the factors behind the high PCD. From the results of self-consistent theoretical calculations of current–voltage characteristics using box-shaped potentials as a first approximation and considering space charge effects of quantum wells, heavy-hole-to-heavy-hole and light-hole-to-light-hole state transitions under the tunneling conditions of the TB potential structure applied in this study were found to be inherent current paths. Moreover, the light and heavy hole currents contribute almost equally to the overall device current, resulting in a theoretical PCD of 637 kA/cm2, which is close to the experimental result. Further analytical simulations with adjusted series resistance and thickness of the nondoped layer allowed the alignment of the theoretically obtained PCD voltage position with the experimentally obtained one. Thus, the theoretical and analytical calculations explain the operation mechanisms of SiGe/Si p-RTDs, and the proposed fabrication method using our sputter epitaxy method is very useful for the actual production of high-PCD SiGe/Si p-RTDs operating at room temperature.

Record peak current density of over 1500 kA/cm2 in highly scaled AlN/GaN double-barrier resonant tunneling diodes on free-standing GaN substrates

This work demonstrates high-performance AlN/GaN double-barrier resonant tunneling diodes (RTDs) with high peak current density grown by plasma-assisted molecular beam epitaxy on c-plane free-standing GaN substrates, featuring stable and repeatable negative differential resistance (NDR) characteristics at room temperature. By scaling down the barrier thickness of AlN barrier and the lateral mesa size of collector, the record peak current density of 1551 kA/cm2 is achieved along with a peak-to-valley current ratio (PVCR) of 1.24, which is attributed to the reduced resonant tunneling time under thinner AlN barrier and the suppressed external incoherent valley current by reducing the dislocation number contained in the RTD device with the smaller size of collector. By statistically analyzing the NDR performance of RTD devices with different thicknesses of AlN barrier, the average peak current density increases from 145.7 to 1215.1 kA/cm2, while the average PVCR decreases from 1.45 to 1.1, correspondingly, accompanying with a decreased peak voltage from 6.89 to 5.49 V, with downscaling the AlN barrier thickness from 1.5 to 1.25 nm. The peak current density obtained in this work is the highest value among all the reported nitride-based RTDs up until now while maintaining high PVCR value simultaneously, which illustrates that ultra-scaled RTD based on vertical quantum-well structure and lateral collector size is a valuable approach for the development of nitride-based RTDs with excellent NDR characteristics and reveals their great potential applications in high-frequency oscillation sources and high-speed switch circuits.

Designing Sustainable Ethanol Oxidation Catalysts: The Role of Graphene Oxide in NiCuGO Composite Material

The growing world population with the growth of civilization is causing the demand for electric energy to increase every year. For this reason, new energy sources such as fuel cells are becoming more and more needed, especially when they can use renewable fuel such as ethanol. This simple organic alcohol can be easily produced in a fermentation process using organic waste. Its oxidation might be used as a source for electricity; however, due to the lack of proper electrocatalytic materials, such a solution is not popular. A simple method of NiCuGO composite preparation via electrodeposition from a water-based solution containing graphene oxide suspension is proposed. The activity of the prepared material is proven, with higher current densities observed for the composite powder. The highest peak current density is observed for NiCuGO deposited with a higher current density. The observed ipA of 8.6 mA cm−2 has been higher than that reported by other researchers.

Barnacle carapace-chitosan supported highly-efficient nano Al-W alloy electrocatalyst for sustainable bio-glycerol valorization: Environmental impact and cost analyses

For the first time, highly efficient, corrosion resistant, and chemically stable rock barnacle carapace-derived chitosan (CH) supported non-noble nano aluminum-tungsten bimetallic-alloy based bifunctional electrocatalyst has been developed for waste pork lard-derived glycerol (WPLG) electrolysis in NaOH medium, ascertaining sustainability. An indirect bio-glycerol oxidation mechanism has been well executed to produce industrially important glyceric acid (6.65 mmol cm−2 h−1, 79.92% selectivity, ∼90% FE%) and formic acid (1.67 mmol cm−2 h−1, 18.07% selectivity) at the anode at ambient temperature and pressure. However, among the various prepared unsupported and supported nanocomposite electrocatalysts, the optimal aluminum-tungsten alloy anchored over chitosan renovated carbon nanotube (Al:W = 1:2 mole/mole) electrode rendered the lowest onset potential (0.95 V vs. RHE) and highest peak current density (119.61 mA cm−2) for the WPLG electrooxidation at the anode, coupled with H2 generation (28.55 ml cm−2 h−1) in the cathode in a membrane free electrochemical-cell by replacing sluggish oxygen evolution reaction. Comparing the electricity consumption for H2 production from various prepared catalysts, the supported optimum catalyst consumed 9.3% less energy (only 2.9 kWh/m3 H2) and 67.91% less corrosion current density as compared to the unsupported Al/W electrocatalyst, exhibiting excellent stability and durability (>200 cycles) due to good alloy-support interaction. Finally, a comprehensive life cycle impact assessment and life cycle costing of the overall WPLG electrolysis demonstrated 12.29% lower global warming potential (GWP100) while saving 11.03% of the cost compared to commercial glycerol electrolysis, which could procreate an effective approach toward inexpensive catalyst fabrication and its subsequent application for sustainable glycerol electrolysis.

Effect of electropulsing-assisted ultrasonic nanocrystal surface modification on microstructures and hardness of additive manufactured Inconel 718

Additive manufacturing can process parts with complex shapes and has great application potential in the biomedical and aerospace industries. However, additively manufactured parts have a poor surface finish, high porosity, and large tensile residual stresses and thus have poor mechanical properties compared with traditional cast or forged parts. To address this issue, an innovative surface process, namely electropulsing-assisted ultrasonic nanocrystal surface modification (EP-UNSM) technology, is proposed. A pulsed current is exerted on the specimen to improve the metal plasticity during the UNSM processing, thereby increasing the effectiveness of strengthening. The results indicate that compared with UNSM, EP-UNSM can further improve the surface quality, surface hardness and the depth of the plastic deformation layer of the specimen. Moreover, it is observed that UNSM is more effective at higher peak current densities. In addition, compared with continuous current with identical thermal effect, pulsed current can more effectively improve the plasticity of Inconel 718, which proves the existence of the athermal effect of electroplasticity.

Pd Nanoparticle-Decorated Novel Ternary Bi2O2CO3-Bi2MoO6-CuO Heterojunction for Enhanced Photo-electrocatalytic Ethanol Oxidation.

Recently, photo-electrooxidation of fuel using a noble metal-semiconductor junction has been one of the most promising approaches in fuel cell systems. Herein, we report the development of a Pd-supported Bi2MoO6-Bi2O2CO3-CuO novel ternary heterojunction for ethanol oxidation in alkali in the presence and absence of visible light. Various spectroscopic and microscopic characterization techniques confirm strong coupling between palladium nanoparticles and Bi2MoO6-Bi2O2CO3-CuO ternary heterojunction supports. The photo-electrocatalytic efficacy of the synthesized catalysts was inspected by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The CV study reveals that the forward peak current density (in mA mg-1 of Pd) of the synthesized quaternary heterojunction was about 1482.5, which is 2.4, 4, and 4.6 times higher than that of Pd/CuO (608.3), Pd/Bi2MoO6-Bi2O2CO3 (368.3), and similarly synthesized Pd catalyst (321.5) under visible light radiation. The best heterojunction catalyst shows 2.21-fold higher peak current density in visible light compared to that in dark. CA study reveals that after operation for 6000 s, the current density of the quaternary electrode is 1.5 and 3.4 times greater than that of Pd/CuO and Pd/C catalysts, respectively. The greater photocurrent response, lower photoluminescence (PL) emission intensity, and smaller semicircle arc in the Nyquist plot of the quaternary catalyst demonstrate the efficient segregation and higher charge transfer conductance of photogenerated charges to facilitate the photo-electrooxidation process of ethanol. The stability test shows that the quaternary catalyst loses only 9.8 and 7.7% of its maximum current density after 500 cycles of CV operation in the dark and light, respectively, indicating that light energy is more beneficial in establishing high stability. The dramatic enhancement of the photo-electrocatalytic activity of the quaternary electrode is owing to the lower band gap, high ECSA, enhanced charge separation of photogenerated carriers (e--h+), and all cocatalytic support of Bi2MoO6, Bi2O2CO3, and CuO in Pd/ Bi2MoO6-Bi2O2CO3-CuO under visible light radiation. The morphology and structure of the used quaternary catalyst are tested using FESEM and PXRD. Finally, ex situ FTIR spectroscopy and HPLC techniques help understand the ethanol electrooxidation reaction mechanism.

Promotion effects of Pr-doped CeO2·H2O to Pt catalysts toward alcohol electrooxidation reaction

Considering that the co-catalyst which are rich in oxygen vacancy and hydroxyl functional groups have an obvious role in improving the activity and durability of Pt-based electrocatalyst, a novel Pr-doped CeO2·H2O cocatalyst (PrxCey(OH)a) has been prepared through a facile one-step hydrothermal method. The substitution of Pr3+ cation for host Ce4+ cation produces oxygen vacancies due to charge compensation effects. Pt/C-Pr1Ce6(OH)a exhibits an outstanding electrochemical oxidation performance with high peak current density of 2587 mA mg−1, 4116 mA mg−1, 2158 mA mg−1 in methanol, ethylene glycol, and glycerol oxidation reaction, respectively. PrxCey(OH)a provides significant co-catalysis effects by comparing with the alcohol electrooxidation performance of Pt/C, which shows a feasible strategy for the rational design of direct alcohol fuel cells catalysts.

High-Performance Zn-I2 Batteries Enabled by a Metal-Free Defect-Rich Carbon Cathode Catalyst.

Aqueous iodine-zinc (Zn-I2) batteries based on I2 conversion reaction are one of the promising energy storage devices due to their high safety, low-cost zinc metal anode, and abundant I2 sources. However, the performance of Zn-I2 batteries is limited by the sluggish I2 conversion reaction kinetics, leading to poor rate capability and cycle performance. Herein, we develop a defect-rich carbon as a high-performance cathode catalyst for I2 loading and conversion, which exhibits excellent iodine reduction reaction (IRR) activity with a high reduction potential of 1.248 V (vs Zn/Zn2+) and a high peak current density of 20.74 mA cm-2, superior to a nitrogen-doped carbon. The I2-loaded defect-rich carbon (DG1100/I2) cathode achieves a large specific capacity of 261.4 mA h g-1 at 1.0 A g-1, a high rate capability of 131.9 mA h g-1 at 10 A g-1, and long-term stability with a high retention of 88.1% over 3500 cycles. Density functional theory calculations indicated that the carbon seven-membered ring (C7) defect site possesses the lowest adsorption energies for iodine species among several defect sites, which contributes to the high catalytic activity for IRR and the corresponding electrochemical performance of Zn-I2 batteries. This work offers a defect engineering strategy for boosting the performance of Zn-I2 batteries.

NiO/MoO2/MoO3 prepared by normal pulse voltammetry as cathode catalysts to investigate the properties of microbial electrolysis cells

AbstractBACKGROUNDA microbial electrolysis cell (MEC) is a bio‐hydrogen production device that uses electrochemically active bacteria on the anode combined with applied voltage to break down organic matter. However, the effects of element content on cathode reduction and cathode catalysts on bioanode activity remain unknown.RESULTSMEC cathodes with different content of Na2MoO4·2H2O (i.e. 0 g L−1 (Ni), 12.5 g L−1 (Ni–Mo 1), 25 g L−1 (Ni–Mo 2) and 37.5 g L−1 (Ni–Mo 3)) were fabricated by normal pulse voltammetry to evaluate the cathode performance. Nanoparticles of Ni electrode are crystalline NiO on the carbon fiber surface. Compared with the Ni electrode, the catalysts of Ni–Mo electrodes are composed of smaller crystalline NiO and amorphous Mo oxides. The results of electrochemical analysis confirmed that Ni–Mo 1 exhibited low exchange transfer resistance (148.72 Ω), high electrochemically active surface area and strong conductivity, resulting in optimal electrocatalysis performance. The newly fabricated electrodes are applied as cathodes in single‐chamber MEC reactors and inoculated with activated sludge from a municipal wastewater treatment plant. High peak current density determined using cyclic voltammetry of the bioanode indicated the strong electrochemical activity of electroactive bacteria in the bioanode of Ni–Mo 1. This is because the low resistance in the MECs could accelerate electron transfer and boost electrochemical reaction.CONCLUSIONSThe performance of cathodes with different Ni and Mo content in terms of electrochemical activity was evaluated. Consequently, the optimal cathode electrode in MECs was Ni–Mo 1. The obtained results reveal that the cathode affects the bioanode activity in MECs. © 2023 Society of Chemical Industry (SCI).

Flower-like Layered NiCu-LDH/MXene Nanocomposites as an Anodic Material for Electrocatalytic Oxidation of Methanol

Direct methanol fuel cell (DMFC) technology has grabbed much attention from researchers worldwide in the realm of green and renewable energy-generating technologies. Practical applications of DMFCs are marked by the development of highly active, efficient, economical, and long-lasting anode catalysts. Layered double hydroxide (LDH) nanohybrids are found to be efficient electrode materials for methanol oxidation. In this study, we synthesized NiCu-LDH/MXene nanocomposites (NCMs) and investigated their electrochemical performance for methanol oxidation. The formation of NCM was verified through field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), and X-ray photoemission spectroscopy (XPS) analyses. The cyclic voltammetry, chronoamperometry, and electron impedance spectroscopy techniques were carried out to assess the electrocatalytic ability of the methanol oxidation reaction. The incorporation of MXene enhanced the methanol oxidation 2-fold times higher than NiCu-LDH. NCM-45 exhibited high peak current density (86.9 mA cm-2), enhanced electrochemical active surface area (7.625 cm2), and long-term stability (77.8% retention after 500 cycles). The superior performance of NCM can be attributed to the synergistic effect between Ni and Cu and, further, the electronic coupling between LDH and MXene. Based on the results, NCM nanocomposite is an efficient anodic material for the electrocatalytic oxidation of methanol. This study will open the door for the development of various LDH/MXene nanocomposite electrode materials for the application of direct methanol fuel cells.

Synthesis and applications of highly stable silane modified reduced graphene oxide supported cobalt based platinum nanoparticle for anodic part of direct methanol fuel cells

In this study, the effects of silane on bimetallic nanoparticles modified with reduced graphene oxide were investigated for direct methanol fuel cells. In this direction, PtCo bimetallic nanoparticles were produced using the chemical reduction method. PtCo@NH2-rGO catalyst was obtained by combining these nanoparticles on 3-Aminopropyltriethoxysilane (APTES) modified reduced Graphene Oxide (rGO). Characterization of the PtCo@NH2-rGO catalyst was performed by X-Ray Diffractometry (XRD), Fourier Transform Infrared (FTIR), and UV–Visible Spectrophotometer (UV-VIS). The methanol oxidation performances of the obtained catalysts were investigated in order to observe the electrochemical effect of NH2-rGO supporting agent on unsupported PtCo and supported PtCo (PtCo@NH2-rGO) catalysts. The PtCo@NH2-rGO electrocatalyst showed a high oxidation peak current density (86.02 mA/cm2) for the anodic portion of the direct methanol fuel cell. This result shows the high performance of the NH2-rGO supported catalyst for direct methanol fuel cells. The resulting catalyst gives promise for potential direct fuel cell applications.