Catalytic Activity In Reaction Research Articles

Screening for electrocatalytic reduction of N2 by borophene supported bimetallic atoms

Ammonia (NH3), as a high energy density chemical and hydrogen energy storage medium, has garnered significant interest in the realms of energy storage and catalysis. In contrast to the traditional Haber-Bosch process, the electrocatalysis nitrogen reduction reaction (eNRR) can synthesize green ammonia under mild reaction conditions. Based on density functional theory (DFT), the potential of 2D borophene supported transition metals as bimetallic atomic catalysts (BACs) in eNRR was investigated. Progressive screening through energy-oriented screening mechanism, Sc2B12, Ti2B12, V2B12 and Zr2B12 were identified as potential eNRR catalysts. Their complete reaction pathways and Gibbs free energy (ΔG) were further explored, and corresponding overpotentials were obtained. The results showed that overpotentials of the potential determining steps (PDS) of these catalysts were 0.34, 0.40, 0.39 and 0.13 V, respectively, demonstrating excellent eNRR catalytic activity and good selectivity. Cu2B12 shows remarkable hydrogen evolution reaction (HER) catalytic activity with an overpotential (η) of only 0.05 V. The study also revealed that the catalytic activity of TM2B12 is derived from its excellent conductivity, and the charge transmission enhances the catalyst activity of eNRR. Consequently, this study provides significant theoretical guidance and support for the synthesis of novel eNRR catalysts, and promotes further advancement in the field of catalysis.

Performance of Co9S8/Cu2S@LDH nanowires prepared by dual sulfur sources to promote oxygen evolution performance

Hydrogen production through water electrolysis is an effective method for obtaining clean energy. The oxygen evolution reaction plays a key role in the process of water electrolysis, and the development of efficient and stable oxygen evolution electrocatalysts is crucial to improve the efficiency of hydrogen production. This paper presents the preparation of Co9S8/Cu2S@LDH nanowire catalysts on copper foam using thiourea and sodium sulfide as dual sulfur sources by a hydrothermal method combined with electrochemical deposition. The composition, structure, and performance of the catalysts were investigated using characterization methods of XRD, SEM, Raman, and electrochemical analyses. Also, the mechanism of thiourea's role in the process of sulfurization of dual sulfur sources was also revealed. The results indicate that the introduction of thiourea facilitates the generation of the active center CoOOH and improves the catalytic efficiency of oxygen precipitation with a low overpotential of 199 mV at 10 mA/cm2 in 1.0 M KOH electrolyte. Additionally, the LDH deposited in the outer layer effectively prevents the oxidation of Co9S8/Cu2S and improves the catalyst's stability. Therefore, the prepared Co9S8/Cu2S@LDH nanowire catalyst exhibits high oxygen evolution reaction (OER) catalytic activity and stability in alkaline electrolyte, making it a promising OER catalyst.

High-performance pyrite nano-catalyst driven photothermal/chemodynamic synergistic therapy for Osteosarcoma

Osteosarcoma (OS) is an aggressive bone tumor with strong invasiveness, rapid metastasis, and dreadful mortality. Chemotherapy is a commonly used approach for OS treatment but is limited by the development of drug resistance and long-term adverse effects. To date, OS still lacks the curative treatment. Herein, we fabricated pyrite-based nanoparticles (FeS2@CP NPs) as synergetic therapeutic platform by integrating photothermal therapy (PTT) and chemo-dynamic therapy (CDT) into one system. The synthetic FeS2@CP NPs showed superior Fenton reaction catalytic activity. FeS2@CP NPs-based CDT efficaciously eradicated the tumor cells by initiating dual-effect of killing of apoptosis and ferroptosis. Furthermore, the generated heat from FeS2@CP under near-infrared region II (NIR-II) laser irradiation could not only inhibit tumor’s growth, but also promote tumor cell apoptosis and ferroptosis by accelerating •OH production and GSH depletion. Finally, the photothermal/NIR II-enhanced CDT synergistic therapy showed excellent osteosarcoma treatment effects both in vitro and in vivo with negligible side effects. Overall, this work provided a high-performance and multifunctional Fenton catalyst for osteosarcoma synergistic therapy, which provided a pathway for the clinical application of PTT augmented CDT.

Experimental characterization and non-isothermal simulation of a zero-gap alkaline electrolyser with nickel-iron porous electrode

The availability of self-supported porous electrodes with excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic activity has been an important cornerstone for the performance of alkaline water electrolysers (AWEs). In addition, the management of heat and two-phase flow during ion/electron transfer in porous electrodes poses significant challenges to the stable operation of AWE electrolysers. In this work, a two-dimensional non-isothermal multiphysical model considering two-phase flow, mass, heat and charge transfer processes is developed based on COMSOL Multiphysics and well validated with reliable experimental data. The model exhibits excellent agreement with actual electrolyser operating voltages between 323–343 K, and the relative error is within acceptable 2.2% even at high current densities up to 1.5 A cm−2. In addition, the electrode kinetic data obtained based on standard three-electrode experiments allow the model to predict the corresponding HER and OER overpotentials of the porous electrodes with great accuracy, as well as to obtain the distribution of temperature and ionic species inside the porous electrodes under various volumetric flow rates and current densities. This work provides a practical and reliable guide for the design of porous electrodes and the performance enhancement of electrolysers from both experimental and simulation perspectives.

Ce-doping enhanced ORR kinetics and CO2 tolerance of Nd1-xCexBaCoFeO5+δ (x = 0–0.2) cathodes for solid oxide fuel cells

Addressing challenges in oxygen reduction efficiency and CO2 endurance is essential for advancing the electrochemical energy conversion performance of solid oxide fuel cells (SOFCs). This investigation introduces an innovative strategy by employing Ce doping to enhance the oxygen reduction kinetics and CO2 resistance of NdBaCoFeO5+δ (NBCF) cathodes. Ce doping effectively regulates the oxygen vacancy content, the ratio of Co3+/Co4+ and Fe3+/Fe4+ in NBCF, leading to substantial improvements in oxygen exchange, lattice diffusion, and charge transfer processes. Consequently, a significant enhancement in the oxygen reduction reaction catalytic activity and CO2 endurance is achieved. At 800 °C, the introduction of 10 mol% Ce doping results in a 65.3% reduction in Rp, reaching 0.024 Ω cm2. Simultaneously, the power density experiences a 50.8% enhancement, reaching 1.0 W cm−2. The current investigation presents a novel avenue towards the advancement of next-generation high-efficiency and stable cathode materials for SOFCs.

P-Ni co-doped Mo2C embedded in carbon-fiber paper as a highly efficient electrocatalyst for hydrogen evolution in alkaline media

The development of noble-metal-free electrocatalysts with high electrocatalytic performance and stability by adopting a scalable route is key to solving the energy crisis. We report a PNi co-doped Mo2C-based electrocatalyst with high hydrogen evolution reaction (HER) catalytic activity prepared by a molten-salt method. Using phosphating times of 2 h and 4 h yielded P-Ni-Mo2C-2h and P-Ni-Mo2C-4h, respectively, both of which exhibited nanoflower-like structures that provided abundant active sites for the reaction. P-Ni-Mo2C-2h possessed good electrocatalytic properties with a low overpotential of only 140.5 mV at j = 10 mA cm−2 and a small Tafel slope of 50.7 mV dec−1 in an alkaline environment. P-Ni-Mo2C-2h exhibited excellent stability after 20 h of continuous hydrogen production. The use of an excessively long phosphating time caused a narrow down of spaces formed by nanoflakes, thereby reducing the HER performance of the electrocatalyst. The results of this study provide guidelines for the preparation of high-efficiency PNi co-doped electrocatalysts.

Regulating the coordination environment of atomically dispersed Fe-N4 moieties in carbon enables efficient oxygen reduction for Zn-air batteries

Fe-N-C single-atom catalysts exhibit the highest oxygen reduction reaction catalytic activity among reported transition metal-based SACs. However, the intrinsic activity of atomically dispersed Fe-N4 moieties in carbon limits the ORR catalytic activity of current Fe-N-C. This work describes a simple method for synthesizing single-atom catalysts with atomically dispersed FeN4CxSy active sites, referred to as FeZ-N/S0.6-C. It also developed a radical polymerization approach to encapsulate ZnCl2 and [Fe(Phen)3]3+ within a polyacrylamide matrix. Due to abundant -CO and –NH2 groups in polyacrylamide, the Zn2+ and Fe complexes could be evenly distributed throughout the polymer. Subsequent one-step pyrolysis allowed the generation of nitrogen-sulfur co-doped catalysts with well-defined pore structures and uniform active sites. The introduction of S atoms by ammonium persulfate extended the Fe-N bond of the Fe-N4 moiety, while the ZnCl2 template aided in fine-tuning the channels within the catalyst. As a result, the FeZ-N/S0.6-C catalyst showed a record high half-wave potential (E1/2 = 0.93 V vs. RHE) among the reported non-noble metal catalysts regulated by S elements. Moreover, FeZ-N/S0.6-C-based aqueous Zn-air and quasi-solid Zn-air batteries achieved excellent performance and showed great application potential in energy storage and conversion devices. This work provides a new approach to encapsulate metal ions in polymers and optimize the single-atom catalyst structure by heteroatom doping to enhance the performance for sustainable applications.

FeN3S1─OH Single-Atom Sites Anchored on Hollow Porous Carbon for Highly Efficient pH-Universal Oxygen Reduction Reaction.

Regulating the asymmetric active center of a single-atom catalyst to optimize the binding energy is critical but challenging to improve the overall efficiency of the electrocatalysts. Herein, an effective strategy is developed by introducing an axial hydroxyl (OH) group to the Fe─N4 center, simultaneously assisting with the further construction of asymmetric configurations by replacing one N atom with one S atom, forming FeN3S1─OH configuration. This novel structure can optimize the electronic structure and d-band center shift to reduce the reaction energy barrier, thereby promoting oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities. The optimal catalyst, FeSA-S/N-C (FeN3S1─OH anchored on hollow porous carbon) displays remarkable ORR performance with a half-wave potential of 0.92, 0.78, and 0.64V versus RHE in 0.1m KOH, 0.5m H2SO4, and 0.1m PBS, respectively. The rechargeable liquid Zn-air batteries (LZABs) equipped with FeSA-S/N-C display a higher power density of 128.35mWcm-2, long-term operational stability of over 500h, and outstanding reversibility. More importantly, the corresponding flexible solid-state ZABs (FSZABs@FeSA-S/N-C) display negligible voltage changes at different bending angles during the charging and discharging processes. This work provides a new perspective for the design and optimization of asymmetric configuration for single-atom catalysts applied to the area of energy conversion and storage.

Self-reduced MXene-Metal interaction electrochemiluminescence support with synergistic electrocatalytic and photothermal effects for the bimodal detection of ovarian cancer biomarkers

Novel two-dimensional MXene with unique optical and electrical properties has become a new focus in the field of sensing. In particular, their metallic conductivity, good biocompatibility and high anchoring ability to biomaterials make them attractive candidates. Despite such remarkable properties, there are certain limitations, such as low oxidative stability. MXene-Metal interactions are an effective strategy to maintain the long-term stability of MXene, while also improving the electrochemical activity and optical properties. Herein, a series of MXene/Ag nanocomposites including Ti3C2/Ag, Nb2C/Ag and V2C/Ag were designed based on the surface chemistry characteristics of MXene, where MXene served as the substrate for in-situ growth of silver nanoparticles via self-reduction of Ag(NH3)2+. The results showed that V2C MXene has the strongest self-reducing ability due to its multiple variable valence states, larger interlayer space and more reactive groups. Moreover, V2C/Ag exhibited unexpected oxygen reduction reaction catalytic activity and photothermal performance. In view of which, an electrochemiluminescence-photothermal (ECL-photothermal) immunosensor was developed using V2C/Ag as ECL anchor and photothermal reagent for ultrasensitive detection of Lipolysis stimulated lipoprotein receptor. This work not only provides a simple and effective synthesis method of MXene supported metal nanocomposites, but also provides more inspirations for exploring the efficient biosensing strategies.

Alleviating anode flooding by mesoporous carbon supports for alkaline polymer electrolyte fuel cells

Water management is one of the critical issues affecting the performance and stability of alkaline polymer electrolyte fuel cells (APEFCs). This study focuses on the effect of carbon supports on the water management of APEFCs. A series of carbon-supported Ru catalysts (Ru/MCP-x) were prepared using mesoporous carbon powder (MCP-x) with three-dimensional through-nanopore structures as supports and compared with Ru/XC72. The results show that although the catalysts’ hydrogen oxidation reaction (HOR) catalytic activities are similar in KOH solutions, the APEFCs performance can be severely different. APEFCs assembled with Ru/MCP-x and Ru/XC72 (noted as Ru/MCP-x cell and Ru/XC72 cell) have little performance difference at high inlet H2 flow (1000 mL/min), but have a noticeable difference at low inlet H2 flow (200 mL/min). By combining the electrochemical AC impedance and distribution of relaxation time (DRT) method, we quantitatively identify that severe gas transfer resistance occurred in the anode catalyst layer of the Ru/XC72 cell under low inlet H2 flow, which is more in line with the actual APEFCs operating conditions, led to considerable degradation of the Ru/XC72 cell performance. The high gas transfer resistance is later ascribed to the anode flooding by combining the voltammetry curves and DRT plots. In contrast, for Ru/MCP-x cells, increasing the carbon supports’ mesopore diameter dramatically reduced the gas transfer resistance and mitigated the anode flooding. This study shows a quantitative comparison of the impacts of different carbon supports on APEFCs performance and gas transfer resistance, indicating that mesoporous carbon materials have the potential to be supports for APEFCs anode catalysts to alleviate the anode flooding.

Lithium doping enhanced ORR kinetics and CO2 tolerance of iron-based double perovskite cathode for solid oxide fuel cells

Fe-based double perovskites exhibit significant potential as cathode materials for solid oxide fuel cells (SOFCs) owing to their affordability, moderate thermal expansion, and impressive stability. Nevertheless, their practical utility has been constrained by their comparatively lower oxygen reduction reaction (ORR) catalytic activity. In this study, for the first time, lithium (Li) was employed as a dopant to improve the ORR activity of the Fe-based double perovskite PrBaFe2O5+δ (PBFO). The results indicated that the ratios of Fe3+/Fe2+ and Oads/Olat were effectively tuned by incorporating Li at Ba-sites of PBFO. Consequently, the adsorption and dissociation of oxygen, along with the charge transfer processes were regulated significantly, resulting in an increase in ORR kinetics and improved CO2 resistance. At 800 °C, PrBa0.9Li0.1Fe2O5+δ (PBLFO) demonstrated an Rp of 0.072 Ω cm², which was decreased by 43.3% compared to PBFO. Simultaneously, the maximum power density of PBLFO-based full cell was improved by 23.3%, reaching 670 mW cm−2. These findings suggest that Li-doping holds great potential for improving the performance of Fe-based SOFC cathodes, thereby contributing to the advancement of clean and sustainable energy technologies.

Room Temperature Corrosion Behavior of Selective Laser Melting (SLM)-Processed Ni-Fe Superalloy (Inconel 718) in 3.5% NaCl Solution at Different pH Conditions: Role of Microstructures

Inconel 718 (UNS N07718) is a nickel-base superalloy containing iron that is used at cryogenic temperatures (arctic pipe components) and at high temperatures (gas turbines). This alloy is also used in off-shore oil drilling due to its high overall strength and resistance to corrosion. Inconel 718 components are created by a selective laser melting (SLM) additive manufacturing route and result in isotropic fine-grained microstructures with metastable phases (such as Laves phases) that are not usually present in conventional manufacturing processes. In this work, SLM Inconel 718 alloy specimens were investigated in four different conditions: (1) As-manufactured (AS-AM), (2) Additively manufactured and hot isostatically pressed (AM-HIP), (3) As-manufactured and heat-treated (solution annealing followed by two-step aging), and 4) AM-HIP and heat-treated. Localized corrosion behavior was evaluated at room temperature in a 3.5% NaCl solution at three different pH conditions (pH 1.25, 6.25, and 12.25). Electrochemical tests, including linear polarization, cyclic polarization, potentiostatic conditioning, electrochemical impedance spectroscopy, and Mott–Schottky analyses, were used to compare the corrosion behaviors of the SLM specimens with that of the conventionally wrought IN718 samples. The results showed that the additively manufactured specimens showed better corrosion resistance than the wrought material in the acidic chloride solution, and the AM-HIP specimens exhibited superior corrosion resistance to the as-manufactured ones. Hot isostatic pressing resulted in the visible elimination of the dendritic structure, indicating compositional homogeneity as well as a significant decrease in porosity. In addition, the deleterious secondary phases, such as Laves and δ phases, were not observed in the microstructure of the HIPed samples. The AM-HIP material showed the highest corrosion resistance in all the pH conditions. The two-step aging treatment, in general, resulted in the deterioration of corrosion resistance, which could be attributed to the formation of γ′ and γ″ precipitates that increased the cathodic reaction catalytic activities. In the additively manufactured samples, the presence of the Laves phase was more detrimental to corrosion resistance than any other phases and MC carbide and grain boundary δ phase increased the susceptibility to corrosion in wrought materials.

One-step microwave synthesis of self-supported NiCoMn medium-entropy alloy with long cycling stability for supercapacitors and oxygen evolution reaction

This work reports the preparation of NiCoMn medium-entropy alloys and Ag-Bi bimetallic alloys grown on nickel foam using the microwave method. X-ray diffraction confirms the single face-centered cubic phase organization of NiCoMn. Electrochemical analyses show that it has a high capacitance of 3206 F g–1 at 1 A g–1 and remarkable cycle stability (83.0 % retention over 70,000 cycles). The Ag-Bi alloys manifest a decent storage capacity of 2462.5 F g–1. To meet the demand for high energy density, the prepared NiCoMn and Ag-Bi are used as positive and negative electrodes to assemble an asymmetric supercapacitor, respectively. The energy density of 218.8 Wh kg–1 is exhibited when the operating voltage is set to 1.5. The NiCoMn alloys also show favorable oxygen evolution reaction catalytic activity, with a low overpotential (186.6 mV) at 10 mA cm–2 and a small Tafel slope (79.6 mV dec–1).

Cation distribution: a descriptor for hydrogen evolution electrocatalysis on transition-metal spinels

The distribution of cations in spinel structures significantly influences their hydrogen evolution reaction (HER) catalytic activity, as it affects the material's electronic properties, stability, and surface characteristics.

First-principle calculations study of the ORR/OER electrocatalytic activity of ruthenium polyphthalocyanine axially modified with aliphatic thiol groups.

In this study, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity of ruthenium polyphthalocyanine axially modified with different aliphatic thiol groups, RuPPc-SR (SR = -SCH3, -SC2H5, -SC3H7, -SC4H9, -SC5H11, and -SC6H13), in an acidic medium were simulated using DFT. All -SR groups can effectively enhance the ORR and OER catalytic activities of RuPPc. The ORR and OER overpotentials of RuPPc-SC4H9 are 0.237 V and 0.436 V, respectively, which are far lower than those of RuPPc (0.960 V and 0.903 V). For RuPPc-SC4H9, the four C and S atoms of the -SC4H9 chain and Ru atom are coplanar, and thus, conjugate effects and inductive effects exist between the -SC4H9 chain and Ru atom. This makes the Ru atom exhibit the least positive Bader charge and smallest spin density, and the anti-bonding orbitals of dxz, dyz, and dz2 of the Ru atom shift below the Fermi level (Ef). This makes the adsorption strength of RuPPc-SC4H9 toward ORR and OER intermediates the weakest, which accelerates the reaction process, thus resulting in better ORR and OER catalytic activity. Therefore, the introduction of the aliphatic thiol groups might effectively improve the OER/ORR catalytic activity of RuPPc.

First-principles studies of enhanced oxygen reduction reactions on graphene- and nitrogen-doped graphene-coated platinum surfaces.

Developing innovative platinum-based electrocatalysts and enhancing their efficiency are crucial for advancing high-performance fuel cell technology. In this study, we employed DFT calculations to provide a theoretical basis for interpreting the impact of graphene coatings on various Pt surfaces on oxygen reduction reaction (ORR) catalytic activity, which are currently applied as protective layers in experiments. We comprehensively assess the geometric and electronic properties of Pt(100), Pt(110), and Pt(111) surfaces in comparison to their graphene-coated counterparts, revealing different adsorption behaviors of O2 across these surfaces. The ORR mechanisms on different Pt surfaces show distinct rate-determining steps, with Pt(111) showing the highest ORR activity, followed by Pt(110) and Pt(100). Graphene coatings play a key role in enhancing charge transfer from the surface, resulting in modifications of O2 adsorption. Despite influencing ORR kinetics, these graphene-coated surfaces demonstrate competitive catalytic activity compared to their bare counterparts. Notably, Pt(111) with a graphene coating exhibits the lowest activation energy among graphene-coated surfaces. Our calculations also suggest that the ORR can occur directly on non-defective Pt@graphene surfaces rather than being restricted to exposed Pt centers due to point defects on graphene. Furthermore, our work highlights the potential of nitrogen doping onto the Pt(111)@C surface to further enhance ORR activity. This finding positions nitrogen-doped Pt@C as a promising electrocatalyst for advancing electrochemical technologies.

Catalytic effects of graphene structures on Pt/graphene catalysts.

Pt/C catalysts have been considered the ideal cathodic catalyst for proton exchange membrane fuel cells (PEMFCs) due to their superior oxygen reduction reaction (ORR) catalytic activity at low temperatures. However, oxidation and corrosion of the carbon black support at the cathode result in the agglomeration of Pt particles, which reduces the active sites in the Pt/C catalyst. Graphene supports have shown great promise to address this issue, and therefore, finding out the main structural features of the graphene support is of great significance for guiding the rational construction of graphene-based Pt (Pt/graphene) catalysts for optimized ORR catalysts. In order to systematically study the influence of the structural features of the graphene support on the electro-catalytic properties of Pt/graphene catalysts, we prepared porous nitrogen-doped reduced graphene oxide (P-NRGO), nitrogen-doped reduced graphene oxide (NRGO), treated P-NRGO (TP-NRGO) and reduced graphene oxide (RGO) with different nitrogen species contents (7.76, 7.54, 3.24, and 0.14 at%), oxygen species contents (18.68, 18.12, 6.34 and 21.12 at%), specific surface areas (370.4, 70.6, 347.7 and 276.2 m2 g-1) and pore volumes (1.366, 0.1424, 1.3299 and 1.0414 cm3 g-1). The ORR activity of the four Pt/graphene catalysts when listed in the order of their half-wave potentials (E 1/2) and peak power densities was found to be as Pt/P-NRGO > Pt/NRGO > Pt/TP-NRGO > Pt/RGO. The long-term durability of Pt/P-NRGO for the operation of H2-air PEMFCs is better than that of commercial Pt/C catalysts. The excellent ORR catalytic performance of Pt/P-NRGO compared to that of the other three Pt/graphene catalysts is ascribed to the high nitrogen species content of P-NRGO that can facilitate the uniform dispersion of Pt particles and provide accessible active sites for ORR. The results indicate that the specific surface area (SSA) and heteroatom dopants have strong influence on the Pt particle size, and that the nitrogen species of graphene supports play a more important role than the oxygen species, specific surface area and pore volume for the Pt/graphene catalysts in providing accessible active sites.

Work function induced electron rearrangement of Ru@Ir core-shell nanocatalysts for promoting pH-universal overall water splitting

Water splitting, one of the primary strategies for advancing the utilization of hydrogen production, necessitates the input of external energies to initiate the reaction due to its thermodynamically uphill nature. Nevertheless, Ru-based compounds, which were widely used as benchmark anodic catalysts, facing significant drawbacks such as their susceptibility to dissolution, significantly restrict the overall water splitting efficiency. In this work, we introduce an approach for functionalization through combining Ru nanospheres with Ir to form a Ru@Ir core–shell structure (denoted as Ru@Ir core–shell NSs), which can activate the superior oxygen evolution reaction (OER) catalytic activity, and simultaneously inherit the hydrogen evolution reaction (HER) performance in all-pH condition. The work function difference between Ru and Ir promotes the necessary energetic impetus for electron migration from Ru to Ir, resulting in the charge redistribution. Density functional theory (DFT) calculations confirmed that the Ir shell, acting as an electron acceptor, could effectively trigger electron rearrangement, augmenting the ligand affinity of hydrogen and oxygen intermediates to attain the most favorable energy states, thereby accelerating the kinetics of hydrogen and oxygen evolution. Our suggested core–shell structure approach for manipulating interface charge distribution might find utility in creating other electrocatalysts for water splitting.

Improved pseudocapacitor and water splitting in cobalt-anchored vanadium carbide MXene nanocomposite

Electrochemical capacitors and hydrogen production through water splitting into constituent hydrogen (H2) and oxygen (O2) molecules are promising methods for long-lasting energy storage. This work presents a simple synthesis of a cobalt ion-doped vanadium carbide MXene (Co@V2CTx) nanocomposite, utilized as an effective, durable, and stable electrode for supercapacitors and as an electrocatalyst for water electrolysis. In 1 M KOH, the Co@V2CTx nanocomposite produced a capacitance of 1071 Fg-1 at 5 mVs−1 (more than 8 times that of pristine V2CTx MXene) and an energy and power density of 26.7 Whkg−1 and 325 Wkg-1 respectively at 1 Ag-1. In addition, the Co@V2CTx nanocomposite showed good hydrogen evolution reaction (HER) catalytic activity, exhibiting a minimal overpotential of 103 mV at 10 mAcm−2 and Tafel slope of 83 mVdec−1. The excellent performance of the Co@V2CTx nanocomposite is due to the synergistic effects produced when cobalt ions are intercalated into the vanadium carbide MXene, preventing restacking of sheets and boosting ion transfer. This work presents an easy and effective method for synthesizing MXene-based nanocomposites for energy storage and conversion applications.

Active Electrochemical Catalysts for Ammonia and Hydrogen Evolution Reaction

An environmentally friendly alternative synthesis process is desired to produce NH3 with no CO2 emissions and low energy demand in a sustainable and ecological way in the future. The electrochemical method assisted by earth-abundant materials has been widely utilized for the chemical energy conversion. We have developed new earth-abundant layered structure metal sulfide based materials as active catalysts for electrochemically nitrogen reduction reaction. From electrochemical analysis, the Faraday efficiency of MoS2 and FeS2 for NRR can be achieve to~27% and 14% with good catalytic stability, respectively. The energy profile of the NRR reaction pathway on the catalysts will be performed by the density functional theoretical (DFT) calculation. Besides, there have been lots of studies on hydrogen evolution reaction (HER) catalytic activity using ultralow loading of Pt catalysts or even Pt single atom catalysts as well. However, Pt single atom deposited on the surface of the carbon or metal oxide material showed some drawbacks, such as high possibility of Pt desorption from the supported material in the electrolyte. Our work demonstrated that gold nanodendrites (Au NDs) with high facet surface was chosen as the supported materials for studying the relation between the low loading amount of Pt atoms and reaction mechanism of HER activity. Overall results provides a feasible approach to morphological control of metal sulfide and atomic deposition of Pt element on the specific substrate as active catalysts for NRR and HER applications, respectively.