Electrochemical Surface Research Articles

(Invited) Pilot Power Platform for Integrated Coupled Electrolysis of Furfural to Maleic Acid and Levulinic Acid to Valeric Acid

In recent years it has become evident that electrification of the chemical industry is essential to shift from a fossil based society to a renewable and sustainable one. In this talk, we will address development of a pilot scale setup to upconvert bioderived feedstocks to relevant building blocks for the chemical industry. Specifically, we focused our attention to the concept of paired electrolysis: oxidation of furfural to maleic acid coupled with reduction of levulinic acid to valeric acid within the same electrochemical cell. Within the framework of this mentioned reaction, we will show different steps of the reactions optimization, scale up, process intensification that eventually led to the construction and testing of pilot power platform installation with electrochemical surface area of 1m2 (10 cell stack 1000cm2) andproductivities of about 6kg/day (Figure 1). We will also focus on downstream process needed to go from crude electrolyte to pure maleic acid and pure valeric acid. Finally, we will present insights from technoeconomic analysis.Biography:PERFORM: Highly selective electrochemical conversions (performproject.eu)Figure 1. Developed infrastructure for electrochemical conversion of bioderived feedstocks to maleic acid and valeric acid. Left: upstream electrochemical Power Platform. Right: electrodialysis pilot, first downstream process of maleic acid purification Figure 1

Development of a Rotating Disk Electrode-Based Ru-Leaching AST for PEM Fuel Cell Reformate Anode Ru-Pt/C Catalysts

Extreme heavy-duty (e.g., maritime) applications of PEM fuel cells often require liquid hydrogen carriers as fuel.[1] In the case of methanol, it is mixed with steam and converted to hydrogen and CO2 in a catalytic reformation process.[2] While a multi-step approach, including the water-gas shift reaction and selective oxidation processes, is typically undertaken to fully convert methanol to hydrogen and CO2, low ppm-level amounts of CO remain in the resulting “reformate hydrogen” gas stream.[3] This CO concentration is significantly higher than deemed non-poisonous to the platinum catalyst on the anode (i.e., < 0.2 ppm),[4] and a more CO-tolerant anode catalyst is required. To address this issue, RuPt-alloy nanoparticles supported on carbon are employed, leading to CO-tolerance of the HOR-catalysts on the anode at reformate conditions.[3] However, previous works found that during operation, Ruthenium leaches from the anode catalyst layer and travels through the membrane, subsequently depositing on the platinum nanoparticles, effectively poisoning the cathode Pt/C catalyst and significantly reducing its activity towards the oxygen reduction reaction.[3,5] To eliminate or reduce Ru-leaching from RuPt/C catalysts while retaining its inherent CO-tolerance, efforts tuning the catalyst’s (surface) composition were made. However, as the leaching of Ru in fuel cells occurs over thousands of hours, the use of an accelerated stress test (AST) for reformate anodes is required. In one of our previous efforts, an AST for Ru-leaching in fuel cells was used to study RuPt/C degradation.[3] However, the amount of material, MEA preparation time and AST measurement time required for such a test was found to be too high for catalyst development. Additionally, fuel cell measurement capacity is limited due to its high cost and the quantification of the total amount of Ru-leached remained challenging.In light of this, in this work, we developed an AST aimed at achieving a reliable yet short and less material consuming protocol, enabling us to quantitatively investigate the Ru-leaching of RuPt-materials during catalyst development. This was achieved by using the rotating disk electrode (RDE) configuration, a well-established electrocatalyst characterization and pre-testing method.[6] The RDE-based AST-protocol was developed using three commercial RuPt-catalysts with varying Ru:Pt ratios of 1:1, 1.5:1, and 2:1 while possessing a comparable particle size and electrochemical surface area. Additionally, the commercial catalyst with a 2:1 atomic ratio catalyst was used in a heat-treated form leading to a larger particle size and lower ECSA.The AST-protocol was comprised of a series of voltammetric cycles aimed at aging the catalyst. During the protocol development, the number of aging cycles (100 – 1000), the scan rate (10 – 100 mV s-1), and the upper inversion potential (0.8 – 0.9 VRHE) of the cyclic voltammograms were varied to investigate their influence on catalyst degradation. This was achieved by collecting the electrolyte (Ar-saturated 0.1M H2SO4) after the AST-cycles and subsequent quantification of the dissolved Ru using inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, the change in the surface composition was qualitatively analyzed by comparing the CO-oxidation peak shape and position before and after the AST-cycling. Examples of the ICP-OES and CO-stripping results for the systematic investigation of the influence of cycle number and scan rate on the 1.5:1 Ru:Pt catalyst using an upper inversion potential of 0.85 VRHE are displayed in Figure 1. Based on this rigorous investigation of the parameters influencing Ru-dissolution in an RDE-environment and after the necessary validation of the results found using the finalized protocol in MEA-based testing,[5] the developed protocol could subsequently be applied to self-synthesized RuPt/C materials as well as RucorePtshell-catalysts.In summary, this contribution showcases the development of a reliable rotating disk electrode-based accelerated stress test protocol for Ru-leaching from RuPt/C catalysts. Furthermore, its validation with commercial catalysts as well as its application to self-synthesized PEM fuel cell anode catalysts for use with reformate hydrogen, is presented.

Tailoring Multi-Metallic Phosphide Heterostructures for High Energy Density Hybrid Supercapacitors

Transition metal phosphides have emerged as a cost effective and resourceful materials that gained extreme attention in the energy sector due to deliverance of high capacitance as well as good redox ability comparable with other oxide materials, which makes them budding material for next-generation electrochemical energy storage (EES) systems. Thanks to the metal-phosphorous chelate in the structure which probes the storage mechanism in EES systems. The electrochemical performance can be enhanced by combining multi-metals in the phosphide to collectively utilize the individual features which will increase the charge efficiency. Herein, tri-metallic Ni-Co-Mo-P electrode on Ni-foam substrate was prepared using simplified hydrothermal-calcination-phosphorylation process. The introduction of Mo enhances the electronic conductivity in the trimetallic phosphide electrode which is reflected in the increased electrochemical performance in comparison to NiCoP electrode. Although, Ni-Co-Mo-P electrode delivers superior activity compared to oxide and precursor electrode, however, the capacity retention till 10 A/g was observed to be 60%, which is higher than other prepared electrodes. The enhanced charge storage performance can be attributed to increased number of electrochemical surface area facilitating more redox reactions. The asymmetric supercapacitor device is constructed with Ni-Co-Mo-P // rGO that delivered high energy and power density with satisfactory cyclic capability.

Lithium-Mediated Nitrogen Reduction in a Flow Electrolyzer Cell Using Gas Diffusion Electrodes with Carbon-Based Electrocatalysts

Due to the sluggish kinetics in activating the chemically stable dinitrogen (N2) and the competing hydrogen evolution reaction in aqueous media, recent attention in the field of direct ammonia (NH3) electrosynthesis has been increasingly drawn to the lithium-mediated N2 reduction reaction (LNRR) in tetrahydrofuran (THF)-based non-aqueous electrolyte. In particular, near 100% faradaic efficiency (FE) and/or a current density (j) of 100 mA cm-2 has been demonstrated with unique electrolyte (proton-shuttle additive) and/or electrode designs (expansive electrochemical surface area) in single-compartment cells at elevated N2 pressure (5 – 20 bar).[1,2]A submerged electrode leads to electrolyte flooding and restricts to N2 mass transfer to the electrode surface where electrodeposited Li as an electron mediator is available.[3] However, flow cell electrolyzers containing gas-diffusion electrodes can improve this technology to practical relevance, which features the LNRR on the cathode and hydrogen oxidation reaction (HOR) on the anode. Differing from single-compartment cells, the HOR supplements the ethanol additive (<1 vol%) as the proton source, which not only prevents the oxidative electrolyte degradation but also reduces the energy consumption due to a lower equilibrium anode potential (E0 = 0 VRHE). Gas-diffusion electrodes (GDEs) are used in the few LNRR studies with flow cell configurations, which are prepared by electro- or electroless depositing electrocatalysts (e.g., Pt [4] or PtAu alloy [5]) onto a porous substrate.In this work, carbon-based electrocatalysts (Vulcan XC72R carbon black, battery-grade conductive carbon SUPER C45, and graphitic carbon SFG6L) as low-cost alternatives to previously studied precious metals are assessed for their LNRR performance in flow cells using an HOR anode. In comparison to Vulcan-supported Pt, XC72R and C45 can obtain similar NH3 production rates (rNH3 )and FE at the same . Continuous LNRR at -3 mA cm-2 was demonstrated with linearly increased NH3 production for over 8 h without catalyst layer detachment, which was also verified with open circuit and Ar control experiments (Fig. 1). By presenting the LNRR activity with GDEs spray-coated with carbon-based electrocatalysts, opportunities for future research are suggested, such as novel carbon materials and porous substrates other than SSC for facile N2 mass transfer and Li deposition.

Surface Defects, Ni3+ Species, Charge Transfer Resistance, and Surface Area dictate the Oxygen Evolution Reaction Activity of Mesoporous NiCo2O4 Thin Films

NiCo2O4 has been proven to show high electrocatalytic activity, however facile and inexpensive techniques for preparation of this compound as mesostructured thin film is lacking. In this study, the sol‐gel synthesis of nanocrystalline mesoporous spinel NiCo2O4 thin films by dip‐coating and soft‐templating using the evaporation‐induced self‐assembly approach is reported. The morphology and crystallographic structure were thoroughly probed by various physicochemical characterization techniques collectively validating the development of uniform mesoporous NiCo2O4 architectures crystallizing exclusively in the cubic spinel phase after calcination in air. The surface area of the thin films depended on the calcination temperature. XPS investigations showed that the amount of Ni3+ and defective oxygen species increased for decreasing calcination temperatures. The overall electrochemical surface area, Ni3+ content, charge transfer resistance, and amount of defective oxygen sites were found to collectively control the oxygen evolution reaction performance. After an optimized annealing procedure at 300°C and chronopotentiometric analysis at 10 mA/cm2 for 1.5 h, a low overpotential of 330 mV vs. RHE at 10 mA/cm2 in alkaline solution was achieved. The results highlight the necessity of precise selection of the appropriate calcination temperature and electrochemical pre‐treatment conditions for adjusting the concentration of electrocatalytically active reaction sites of sol‐gel‐derived NiCo2O4 thin films.

Advancing Electrically Conductive Metal-Organic Frameworks for Photocatalytic Energy Conversion.

ConspectusPhotocatalytic energy conversion is a pivotal process for harnessing solar energy to produce chemicals and presents a sustainable alternative to fossil fuels. Key strategies to enhance photocatalytic efficiency include facilitating mass transport and reactant adsorption, improving light absorption, and promoting electron and hole separation to suppress electron-hole recombination. This Account delves into the potential advantages of electrically conductive metal-organic frameworks (EC-MOFs) in photocatalytic energy conversion and examines how manipulating electronic structures and controlling morphology and defects affect their unique properties, potentially impacting photocatalytic efficiency and selectivity. Moreover, with a proof-of-concept study of photocatalytic hydrogen peroxide production by manipulating the EC-MOF's electronic structure, we highlight the potential of the strategies outlined in this Account.EC-MOFs not only possess porosity and surface areas like conventional MOFs, but exhibit electronic conductivity through d-p conjugation between ligands and metal nodes, enabling effective charge transport. Their narrow band gaps also allow for visible light absorption, making them promising candidates for efficient photocatalysts. In EC-MOFs, the modular design of metal nodes and ligands allows fine-tuning of both the electronic structure and physical properties, including controlling the particle morphology, which is essential for optimizing band positions and improving charge transport to achieve efficient and selective photocatalytic energy conversion.Despite their potential as photocatalysts, modulating the electronic structure or controlling the morphology of EC-MOFs is nontrivial, as their fast growth kinetics make them prone to defect formation, impacting mass and charge transport. To fully leverage the photocatalytic potential of EC-MOFs, we discuss our group's efforts to manipulate their electronic structures and develop effective synthetic strategies for morphology control and defect healing. For tuning electronic structures, diversifying the combinations of metals and linkers available for EC-MOF synthesis has been explored. Next, we suggest that synthesizing ligand-based solid solutions will enable continuous tuning of the band positions, demonstrating the potential to distinguish between photocatalytic reactions with similar redox potentials. Lastly, we present incorporating a donor-acceptor system in an EC-MOF to spatially separate photogenerated carriers, which could suppress electron-hole recombination. As a synthetic strategy for morphology control, we demonstrated that electrosynthesis can modify particle morphology, enhancing electrochemical surface area, which will be beneficial for reactant adsorption. Finally, we suggest a defect healing strategy that will enhance charge transport by reducing charge traps on defects, potentially improving the photocatalytic efficiency.Our vision in this Account is to introduce EC-MOFs as an efficient platform for photocatalytic energy conversion. Although EC-MOFs are a new class of semiconductor materials and have not been extensively studied for photocatalytic energy conversion, their inherent light absorption and electron transport properties indicate significant photocatalytic potential. We envision that employing modular molecular design to control electronic structures and applying effective synthetic strategies to customize morphology and defect repair can promote charge separation, electron transfer to potential reactants, and mass transport to realize high selectivity and efficiency in EC-MOF-based photocatalysts. This effort not only lays the foundation for the rational design and synthesis of EC-MOFs, but has the potential to advance their use in photocatalytic energy conversion.

Electrochemical quartz crystal microbalance study of underpotential deposition of mercury on iridium metal and iridium oxide

AbstractTo evaluate the properties of an Ir‐based catalyst (IrOx), which is the anode in polymer electrolyte membrane‐type water electrolysis, a new method for estimating the electrochemical surface area (ECSA) is required. ECSA evaluation using the underpotential deposition of mercury (Hg‐UPD) can be applied to metals and oxides. However, research regarding Hg‐UPD is needed because several Hg(II)/Hg(I) redox reactions occur simultaneously, and direct evidence of Hg‐UPD on IrOx has not been reported. We previously confirmed the Hg‐UPD phenomenon on Ir polycrystalline films using the electrochemical quartz crystal microbalance (EQCM) method. However, measurements on IrOx electrodes were not performed. In this study, Ir and IrOx electrodes are prepared by the sputtering method, and their Hg deposition behavior observed by EQCM. We quantitatively confirm Hg‐UPD on Ir metal surfaces and provide new evidence of Hg‐UPD on the IrOx surface. These results contribute to establishing the ECSA evaluation of various Ir‐based catalysts.

How Microstructures, Oxide Layers, and Charge Transfer Reactions Influence Double Layer Capacitances. Part 2: Equivalent Circuit Models

ABSTRACTIn the first part of this study, double layer (DL) capacitances of plane and porous electrodes were related to electrochemical active surface areas based on electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements. Here, these measured data are described with equivalent circuit models (ECMs), aiming to critically assess the ambiguity, reliability, and pitfalls of the parametrization of physicochemical mechanisms. For microstructures and porous electrodes, the resistive–capacitive contributions of DL in combination with resistively damped currents in pores are discussed to require the complexity of convoluted transmission line ECMs. With these ECMs, the frequency‐dependencies of the capacitances of porous electrodes are elucidated. Detailed EIS or CV data‐based reconstructions of complex microstructures are discussed as impossible due to the blending of individual structural features and the related loss of information. Microstructures in combination with charge transfer reactions and weakly conducting parts require parameter‐rich ECMs for an accurate physicochemical description of all physicochemical mechanisms contributing to the response. Nevertheless, the data of such a complex electrode in the form of an oxidized titanium electrode are fitted by an oversimplistic ECM, showing how easily unphysical parameterizations can be obtained with ECM‐based impedance analysis. In summary, trends in how microstructures, charge transfer resistances and oxide layers can influence EIS and CV data are shown, while awareness for the overinterpretation of ECM‐analysis is raised.

Investigating solvent effects on synthesizing novel cobalt hydroxide and fluoride complex from Co(BF4)2 as active materials of the battery supercapacitor hybrid

Metal-organic framework (MOF) derivatives with tunable pore structure and improved conductivity are intensively designed as electroactive materials. Incorporating structure directing agents (SDA) is beneficial for designing MOF derivatives with excellent electrochemical performances. Ammonium fluoroborate has been reported as an effective SDA, coupled with cobalt salt and 2-methylimidazole, to synthesize zeolitic imidazolate framework-67 (ZIF-67) derivatives for charge storage. However, the synthetic environment for growing cobalt-based active materials is relatively complex. In this study, cobalt tetrafluoroborate (Co(BF4)2) is proposed as a novel cobalt precursor, supplementing cobalt ions and acting as the SDA in a single chemical, to synthesize the cobalt-based electroactive material of energy storage electrodes. Interactions between solvent molecules and solutes play significant roles on the morphology, composition, and electrochemical performance of active materials. Deionized water, methanol and ethanol are used as precursor solvents to understand their effects on material and electrochemical properties. The optimal electrode presents a specific capacitance of 608.3 F/g at 20 mV/s, attributed to the highest electrochemical surface area and evident compositions of cobalt fluoride and hydroxide. A battery supercapacitor hybrid achieves the maximum energy density of 45 Wh/kg at 429 W/kg. The CF retention of 100% and Coulombic efficiency of 99% are achieved after 10,000 cycles.

NiFeP nanosheet arrays supported on nickel nitrogen codoped carbon nanofiber as an efficient bifunctional catalyst for overall water splitting

Transition metal phosphides have emerged as effective electrocatalysts for water splitting. In this study, novel NiFeP nanosheet arrays supported on nickel nitrogen codoped carbon nanofiber (NiFeP@Ni-NCNF) was synthesized through a combination of electrospun, template-directed growth, and phosphorization strategy. The utilization of Ni-NCNF as a substrate for constructing the nanoarrays structure with superhydrophilic and superaerophobic properties significantly enhances the electrochemical active specific surface area of the electrocatalytic material. The synergistic effect of Ni2P and Fe2P and the excellent conductivity of the Ni-NCNF substrate promote NiFeP@Ni-NCNF to exhibit excellent HER/OER electrocatalytic properties. The NiFeP@Ni-NCNF exhibits low overpotentials of 131 mV and 204 mV for HER and OER at 10 mA cm−2, respectively. Additionally, using NiFeP@Ni-NCNF as the anode and cathode of the electrolytic water device displays a voltage of 1.61 V at 10 mA cm−2, and the Faraday efficiency of the two electrodes is near 100 %. This research presents an extensible and cost-effective strategy for synthesizing phosphide-based catalysts with unique nanostructures and desirable water splitting catalytic properties.

Fabrication of Ru-doped CuMnBP micro cluster electrocatalyst with high efficiency and stability for electrochemical water splitting application at the industrial-level current density

Electrochemical water splitting has been considered as a key pathway to generate environmentally friendly green hydrogen energy and it is essential to design highly efficient electrocatalysts at affordable cost to facilitate the redox reactions of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, a novel micro-clustered Ru/CuMnBP electrocatalyst is introduced, prepared via hydrothermal deposition and soaking-assisted Ru doping approaches on Ni foam substrate. Ru/CuMnBP micro-clusters exhibit relatively low HER/OER turnover overpotentials of 11 mV and 85 mV at 10 mA/cm2 in 1 M KOH. It also demonstrates a low 2-E turnover cell voltage of 1.53 V at 10 mA/cm2 for the overall water-splitting, which is comparable with the benchmark electrodes of Pt/C||RuO2. At a super high-current density of 2000 mA/cm2, the dual functional Ru/CuMnBP demonstrates an exceptionally low 2-E cell voltage of 3.13 V and also exhibits superior stability for over 10 h in 1 M KOH. Excellent electrochemical performances originate from the large electrochemical active surface area with the micro cluster morphology, high intrinsic activity of CuMnBP micro-clusters optimized through component ratio adjustment and the beneficial Ru doping effect, which enhances active site density, conductivity and stability. The usage of Ru in small quantities via the simple soaking doping approach significantly improves electrochemical reaction rates for both HER and OER, making Ru/CuMnBP micro-clusters promising candidates for advanced electrocatalytic applications.

Improvement in electrochemical performance of SrTiO3 with rGO via composite (SrTiO3/rGO) strategy fabricated via solvothermal approach

Developing sustainable and highly effective electrocatalysts for the oxygen evolution reaction (OER) is a significant research target for precise custody of water splitting to fulfill worldwide energy demands. This study focuses on the fabrication of SrTiO3/rGO-based composite via a solvothermal technique, which works as an electrocatalyst for evaluating the efficiency of OER in alkaline media. The material displays outstanding OER efficacy in 1 M KOH solution with its cubic structure validated by the X-ray diffraction (XRD) study. The electrochemical study reveals that the SrTiO3/rGO composite has a minimal overpotential (222 mV) compared to SrTiO3 (289 mV) and the commercial catalyst RuO2 (367 mV). The SrTiO3/rGO composite also has a minimal Tafel plot gradient of 37 mV dec−1 whereas RuO2 has a Tafel value of 72 mV dec−1. The current material has superior properties compared to RuO2, a commercial catalyst for the OER. The SrTiO3/rGO composite shows exceptional stability for 40 h. The low conductivity of oxygen-deficient SrTiO3 perovskite can be improved by incorporating carbon-based rGO into it, as demonstrated by the minimal Rct (0.07 Ω) obtained from electrochemical impedance spectroscopy (EIS) analysis and an enlarged surface area of 250 cm2, as evidenced by electrochemical surface area (ECSA). Therefore, our research indicates that a particular morphology of metal oxide can improve the efficiency of electrocatalysis when combined with reduced graphene oxide (rGO), suggesting its potential for generating effective and environmentally friendly energy. Hence, these findings may improve the smooth passage of electrons and provide a novel perspective to function as an adequate substitute for RuO2, a commercial catalyst.

Enhanced efficiency and stability in the degradation of triazophosphorus pesticides by Al6Si2O13/WO2.72 nanocomposites through synergistic action of S-scheme heterojunction and oxygen vacancies

The environmental contamination caused by organophosphorus pesticides (for example, triazophos) is an escalating concern. To mitigate this issue, this study introduces a novel Al6Si2O13/WO2.72 (ASO/WO) nanocomposite photocatalyst, which markedly enhances the photocatalytic degradation of triazophos. The optimized nanocomposite material with a 60.0 % ASO loading (60-ASO/WO) achieves a degradation rate of 86.3 % for triazophos within 140.0 min, marginally exceeding 60-ASO/WO3 (72.6 %) and significantly outperforming individual ASO (65.0 %), WO (59.5 %), and WO3 (56.2 %). This catalyst retains 88.9 % of its activity after five cycles, showcasing exceptional efficiency and stability. Additionally, its electrochemical surface area (ECSA, 310.0 cm2), total organic carbon (TOC, removal rate of 73.7 %), photocurrent, and electrochemical impedance are all optimal. X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and theoretical calculations elucidate the critical role of oxygen vacancies and the S-scheme heterojunction in augmenting charge separation and photocatalytic performance, corroborating the synergistic effect of oxygen defects and the S-scheme. While individual factors can enhance photocatalytic activity, their combination results in a more pronounced effect. Liquid chromatography-mass spectrometry (LCMS) identifies the principal degradation intermediates, including 1-phenyl-3-hydroxy-1, 2, 4-triazole, diethyl thiophosphate, and 3, 5, 6-trichloro-2-pyridinol, underscoring the material’s potential in environmental remediation.

Probing Electrocatalytic Synergy in Graphene/MoS2/Nickel Networks for Water Splitting through a Combined Experimental and Theoretical Lens.

The development of low-cost and active electrocatalysts signifies an important effort toward accelerating economical water electrolysis and overcoming the sluggish hydrogen or oxygen evolution reaction (HER or OER) kinetics. Herein, we report a scalable and rapid synthesis of inexpensive Ni and MoS2 electrocatalysts on N-doped graphene/carbon cloth substrate to address these challenges. Mesoporous N-doped graphene is synthesized by using electrochemical polymerization of polyaniline (PANI), followed by a rapid one-step photothermal pyrolysis process. The N-doped graphene/carbon cloth substrate improves the interconnection between the electrocatalyst and substrate. Consequently, Ni species deposited on an N-doped graphene OER electrocatalyst shows a low Tafel slope value of 35 mV/decade at an overpotential of 130 mV at 10 mA/cm2 current density in 1 M KOH electrolytes. In addition, Ni-doped MoS2 on N-doped graphene HER electrocatalyst shows Tafel slopes of 37 and 42 mV/decade and overpotentials of 159 and 175 mV, respectively, in acidic and alkaline electrolytes at 10 mA/cm2 current density. Both these values are lower than recently reported nonplatinum-group-metal-based OER and HER electrocatalysts. These excellent electrochemical performances are due to the high electrochemical surface area, a porous structure that improves the charge transfer between electrode and electrolytes, and the synergistic effect between the substrate and electrocatalyst. Raman spectroscopy, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations demonstrate that the Ni hydroxide species and Ni-doped MoS2 edge sites serve as active sites for OER and HER, respectively. Finally, we also evaluate the performance of the HER electrocatalyst in commercial alkaline electrolyzers.

New aryl-himachalene benzylamines derivatives as eco-friendly corrosion inhibitors at low concentration for brass 62/38 in 200 ppm NaCl: Experimental, analyses and theoretical approach

This study investigates the inhibitory effect of eco-friendly synthesized aryl-himachalene benzylamines derivatives, namely (±)-N-((3,5,5,9-tetramethyl -6,7,8,9-tetrahydro-5H-benzo [7] annulen-2yl)methyl)aniline (AHB) and (±)-4-bromo-N-((3,5,5,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzo[7]annulen-2-yl)methyl)aniline (AHBBR) at low concentration on the brass 62/38 (B62/38) corrosion in 200 ppm NaCl solution, employing electrochemical techniques, surface analyses and theoretical investigations. The experimental measurements indicated that these compounds exhibit as good inhibitions, where their inhibition efficiency growth with their concentrations, reaching 88.69 % and 93.35 % at 100 ppm AHB and AHBBR, respectively. I-E measurements designated that the tested products react like a mixed-inhibitor type. In addition, the EIS measurements showed the establishment of a protective layer on the B62/38 region. The effects of the temperature solution and immersion time on their performance were investigated. It is found that they decrease slowly with temperature, while they improve with the immersion time until 12 h. In the same way, it is found that these molecules react on B62/38 surface according to Langmuir isotherm adsorption. Complementary, SEM/EDX analysis established the development of an organic defending film on the B62/38 area, confirming the compound's potential as effective corrosion inhibitors. Finally, the theoretical investigations confirm the anti-corrosion character of the tested compounds according to their mode of adsorption.

Energy efficiency and electrochemical characteristic assessment of PEMFC-supercapacitor hybridization via railway profile

Electric trains equipped with efficient electric motors and powered by high-capacity hydrogen fuel cells are a choice of the global transportation industry to accelerate the global transition to a low-carbon transportation system. The operation of distinct vehicle types in varying geographical regions is characterized by unique features. Concurrently, the continually fluctuating demand for electricity necessitates the utilization of fuel cells in conjunction with energy storage devices. Thus, this study centers on examining the role of the PEMFC-supercapacitor direct hybridization system within the authentic driving profile of the subway in the Bangkok metropolitan region. The supercapacitor within the hybridization system serves as an energy management device, enhancing the durability of fuel cells when subjected to diverse load demands associated with train propulsion. In order to validate this hypothesis, an MRT (Mass Rapid Transit) protocol was formulated to emulate and serve as the load demand for the investigation, and then the PEMFC-supercapacitor direct hybridization system was operated using the created profile. Subsequently, the hybridization system undergoes electrochemical characterizations and fuel cell performance tests for diagnostic purposes. Empirical findings validated that the supercapacitor operates as a filter, generating a stable voltage response to varying load requirements, and possesses the capability to assimilate energy originating from regenerative braking. The integration of supercapacitors in stabilizing the operational parameters of proton exchange membrane fuel cells (PEMFCs) has markedly prolonged their operational lifespan. This assertion is substantiated by voltage signal analysis, which demonstrated a negligible increase in surface resistance of merely 0.23%, as depicted by Nyquist plots. Furthermore, cyclic voltammetry revealed that the system attained a peak electrochemical surface area (ECSA) of 0.0089 (106 cm2/mg of Pt). The information presented in this article constitutes data that has been minimally explored in existing research. Specifically, the study concentrates on the practical driving pattern of electric trains. Consequently, experimental results were deemed advantageous for the advancement of heavy-duty electric vehicles.

Liquid Metal-Enabled Tunable Synthesis of Nanoporous Polycrystalline Copper for Selective CO2-to-Formate Electrochemical Conversion.

Copper-based catalysts exhibit high activity in electrochemical CO2 conversion to value-added chemicals. However, achieving precise control over catalysts design to generate narrowly distributed products remains challenging. Herein, a gallium (Ga) liquid metal-based approach is employed to synthesize hierarchical nanoporous copper (HNP Cu) catalysts with tailored ligament/pore and crystallite sizes. The nanoporosity and polycrystallinity are generated by dealloying intermetallic CuGa2 formed after immersing pristine Cu foil in liquid Ga in a basic or acidic solution. The liquid metal-based approach allows for the transformation of monocrystalline Cu to the polycrystalline HNP Cu with enhanced CO2 reduction reaction (CO2RR) performance. The dealloyed HNP Cu catalyst with suitable crystallite size (22.8nm) and nanoporous structure (ligament/pore size of 45nm) exhibits a high Faradaic efficiency of 91% toward formate production under an applied potential as low as -0.3 VRHE. The superior CO2RR performance can be ascribed to the enlarged electrochemical catalytic surface area, the generation of preferred Cu facets, and the rich grain boundaries by polycrystallinity. This work demonstrates the potential of liquid metal-based synthesis for improving catalysts performance based on structural design, without increasing compositional complexity.

Perovskite nanostructure anchored on reduced graphene (rGO) nanosheets as an efficient electrocatalyst for oxygen evolution reaction (OER)

Energy is the basic need of this modern era and water splitting is the best known renewable source of energy. Designing an effective, high performing and durable electrocatalyst has become a serious endeavour to enhance water-splitting efficiency. For this purpose, a hydrothermal method was used to produce a non-toxic, environmentally friendly and cost-effective rGO/ZnSnO3, a composite material to improve water oxidation. For this, various analytical approaches were used to investigate the structural, textural, compositional, thermal and morphological features of the reported materials. The electrochemical properties of the rGO/ZnSnO3 nanohybrid was also analyzed by a three-electrode setup in a 1 M potassium hydroxide (KOH) and the resulting nanohybrid exhibited exceptionally small overpotential (212 mV) at an ideal current density (j) of 10 mA/cm2. The larger electrochemical surface area (ECSA) value 506.25 cm2, minimum charge transfer resistance (Rct) 0.18 Ω and remarkable stability around 20 h revealed that the produced composite material exhibited excellent potential for OER. Further examination revealed a significantly low Tafel value (37 mV/dec), suggesting that the rGO/ZnSnO3 nanohybrid possesses improved electrocatalytic efficiency and fast reaction kinetics. The nanohybrid mentioned above (rGO/ZnSnO3) shows significant potential for electrolysis of water and other electrochemical processes attributed to its considerable surface area, various active sites, exceptional stability, rapid electron mobility, low resistivity and favourable electrical conductivity.

Constructing novel Sn-Mo bimetallic sulfide heterostructures for enhanced catalytic performance towards the hydrogen evolution reaction

Understanding the design principles of efficient electrocatalysts using the structure–activity relationship is crucial for the advancement of energy-related applications, and specifically the hydrogen evolution reaction (HER). Non-precious electrocatalysts with low overpotentials are essential for driving the HER and achieving high energy efficiency. In this study, we synthesized and thoroughly investigated various heterostructures combining Mo and Sn sulfides, ranging from complete phase-separated hybrids to homogeneous mixtures: SnS@MoS2 core–shell structures, SnS/MoS2 with edge-rich Mo and (SnxMo1-x)S with uniformly distributed Sn-Mo. Our findings reveal that the SnS@MoS2 structure exhibited relatively high intrinsic activity characterized by a high electrochemical active surface area and rapid charge transfer kinetics, thereby enhancing the HER catalytic performance. The presence of fluffy MoS2 layers provided an abundance of optimized sites for HER, potentially due to strain and defects such as S vacancies, known as active catalytic sites. The optimal structure facilitated efficient charge transfer from the core to the shell, improving conductivity and catalytic activity. Our research highlights the advantages of a core–shell hybrid structure, offering guiding principles for the development of an optimal SnS@MoS2 catalyst.

Tuning Morphologies of Metal-Organic Framework-Derived Ni3P/Ni Carbon Nanocomposites for Water Oxidation.

The oxygen evolution reaction (OER) frequently acts as a kinetic bottleneck in various energy storage and conversion systems. Effective electrocatalysts for the OER play a crucial role in reducing the reaction barrier and expediting the reaction. Multicomponent transition metal phosphides (TMPs) have garnered an extensive amount of attention as a result of their exceptional performance in the OER. Here, we present a direct method for preparing two intrinsic morphologies of metal-organic frameworks (MOFs), barrel-like BMM-10 and pancake-like BMM-10(Ac), achieved by establishing a protonation/deprotonation equilibrium with varying NO3-/Ac- ratios. The BMM-10(Ac)-C catalyst was synthesized via heat treatment of the BMM-10(Ac) precursor, exhibiting superior OER performance. It realized an overpotential of 286 mV at a current density of 10 mA cm-2, with a Tafel slope of 111.17 mV decade-1 and a current retention of 98.03%. This improvement arises from the synergistic interaction between Ni3P/Ni nanoparticles and the partially graphitic carbon layer, augmenting the exposure of active sites. Furthermore, alterations in the morphological features of MOF-derived Ni3P/Ni carbon nanocomposites adjusted the active electrochemical surface area, thereby modulating the overall OER performance of the corresponding TMP carbon nanocomposites. This methodology can be extended to control the morphology of other MOFs and their derivatives, providing innovative avenues for the design and synthesis of new MOF-based TMP nanomaterials.