Activity In Acidic Media Research Articles

Polyimide-based triazine-cored covalent organic frameworks supported metal (Fe, Ni, Ru and Rh) nanoparticles for high-efficiency electrocatalytic hydrogen evolution

Covalent organic frameworks (COFs) have great potential in electrocatalytic hydrogen evolution reaction (HER). Nevertheless, it is a challenging task to fabricate COF-based electrocatalysts with low overpotential and high stability for HER in acidic media. Herein, a series of polyimide-based triazine-cored COFs (PIT-COFs) with different aromatic diimides are designed to support metal (Fe, Ni, Ru and Rh) nanoparticles for electrocatalytic HER. PIT-COFs are obtained by the reaction between melamine and aromatic (benzene, biphenyl, naphthalene and perylene) diimides. PIT-COFs based on perylenediimide show the optimal electrocatalytic HER activity in acidic media due to its large π-conjugated structure. Rh@COFMA-PT has a low overpotential value of 70 mV at 10 mA cm−2 and a small Tafel slope of 56.58 mV dec−1, which surpasses numerous previously published HER electrocatalysts. Furthermore, Rh@COFMA-PT exhibits good electrocatalytic stability and still keeps high activity after 3000 cycles. The conjugated nitrogen-rich structures of PIT-COFs and their ability to effectively anchor metal nanoparticles as active sites significantly promote the electron and proton transport during the electrocatalytic HER process. This work offers a guideline for developing effective and stable COF-based HER electrocatalysts with abundant active sites.

Design of NiPS3/MoS2/rGO hybrid electrocatalyst for electrochemical hydrogen evolution

The design and development of efficient electrocatalysts for hydrogen evolution reaction is presently a pressing task to overcome future energy demands. In the present study a hybrid layered compound NiPS3/MoS2/rGO (NMR) is investigated as an electrocatalyst for hydrogen evolution reaction (HER). The metal trichalcogenidophosphates (MTPs), transition metal dichalcogenides and reduced graphene oxide materials based electrocatalysts are promising material for HER. The hybrid layered compound NMR displays good electrocatalytic activity in acidic medium in comparison to its counterparts MoS2/rGO and NiPS3/rGO with an overpotential and Tafel slope of 152 mV vs RHE and 75 mV/dec, whereas MoS2/rGO and NiPS3/rGO shows an overpotential of 206 mV and 223 mV vs RHE with a Tafel slope value of 146 mV/dec and 154 mV/dec respectively. The hybrid electrocatalyst exhibited high stability up to 1000 cycles with a stable current. The high HER activity of NMR is attributed to synergistic effect of electrocatalysts where P and S of NiPS3 acts as an appropriate hydrogen adsorption sites and catalytically active Mo edge sites of MoS2 with high charge carrier property of rGO contributed to enhanced hydrogen evolution reaction.

Design of Manganese‐Doped Zinc Oxide Nanoparticles as Effective Electrocatalytic System in Oxygen Reduction Reactions

ABSTRACTFuel cell technologies constitute a clean, reliable, highly efficient, and eco‐friendly source of alternative energy generation. However, they still require a reliable and robust catalytic system showing comparative electrochemical activity to precious metal Pt with less cost. In this work, Mn@ZnO NPs were synthesized using a hydrothermal‐assisted simple method. Several techniques including SEM, TGA, and XRD were used to confirm the material synthesis. Electrochemical properties were analyzed by using linear sweep voltammetry, chronoamperometry, and cyclic voltammetry. A higher ORR activity in terms of mass activity and current density was observed 133.9 mA/mg as compared to Pt/C (96 mA/mg) and Pd/C (67 mA/mg) under otherwise identical conditions. Mn@ZnO also exhibited excellent current density (1.913 mA cm−2), comparable to Pt/C (1.55 mA cm−2). Chronoamperometry shows stability for up to 800 s. Comparative studies were conducted in both acidic and basic mediums, with observed higher ORR activity in acidic media.

Stable and efficient hydrogen evolution activity of tungsten-incorporated nanocrystalline perovskite BaSnO3 electrocatalyst

The increasing demand in energy consumption and alarming environmental concern is compelling to develop alternative renewable and clean energy sources. Hydrogen (H2) is identified as a potential candidate due to its abundance, high gravimetric energy density, and no carbon footprint. Presently, splitting of water is a highly promising method for sustainable hydrogen generation, and the key challenge is to develop a stable and high-performing electrocatalysts for H2 evolution reaction (HER) as a renewable energy source. Metal oxides are excellent alternative electrocatalysts to noble metals due to their cost effectiveness, tunability and abundance. Ternary perovskite barium stannate (BaSnO3) has been intensely explored for water splitting and electrocatalysis related applications. Tungsten (W) 1 % incorporated BaSnO3 synthesized by facile hydrogen peroxide route is explored as an electrocatalyst for HER activity in acidic medium for the first time. The pure and W-incorporated BaSnO3 exhibited promising HER activity with an overpotential value of 233 and 295 mV at 10 mA/cm2 with enhanced electrochemical surface area of 7.309 and 3.075 Fcm−2, respectively. A 12-hour stability test not only concluded the durability and performance of H2 evolution activity but also confirmed the enhanced initial current density for the W-incorporated BaSnO3 sample.

Platinum Cluster Decoration on Hollow Carbon Spheres for High-Efficiency Hydrogen Evolution Reaction.

Currently, platinum (Pt)/carbon support composite materials have tremendous application prospects in the hydrogen evolution reaction (HER). However, one of the primary challenges for boosting their performance is designing a substrate with the desired microstructure. Herein, the intact hollow carbon spheres (HCSs) were prepared via template method. Based on the morphology variation of the as-prepared HCSs-x, we conjectured that the polydopamine (PDA) core was generated first and then slowly grew into a complete overburden (SiO2@PDA). Afterward, Pt atomic clusters were anchored on the outer shells of HCSs-4 to construct composite electrocatalysts (Pty/HCSs-4) by a chemical reduction method. Due to the low charge-transfer resistance, the HCSs have a large electrochemical surface area and provide a continuous electron transport pathway, boosting the atom utilization efficiency during hydrogen production and release. The synthesized Pt2.5/HCSs-4 electrocatalysts exhibit excellent HER activity in acidic media, which can be ascribed to the compositional modulation and delicate structural design. Specifically, when the overpotential is 10 A g-1, the overpotential can achieve 92 mV. This work opens a new route to fabricate Pt-based electrocatalysts and brings a new understanding of the formation mechanism of HCSs.

ZIF-8-derived nanocarbon composite-based highly active platinum group metal-free bimetallic electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Non-precious metal catalysts are ideal low-cost substitutes of Pt/C for the sluggish oxygen reduction reaction (ORR), despite the serious stability challenges in proton exchange membrane fuel cells (PEMFC) to alleviate the energy crisis and environmental problems. Platinum group metal (PGM)-free bimetallic composite electrocatalysts are assumed to be an interesting route to be investigated to address the stability and ORR selectivity related issues in PEMFC conditions. In this regard, we propose a simple and facile synthesis route by a composite of multi-walled carbon nanotubes and zeolitic imidazolate framework (ZIF)-8 followed by impregnating dual transition metals (FeMn, FeCo, and CoMn) and evaluate their ORR activity in acid media and PEMFC performance. Various catalyst materials are prepared and optimized to achieve the highest electrocatalytic performance. The prepared catalysts are characterized by various physico-chemical methods to elucidate their textural, structural, and morphological properties. The high ORR electrocatalytic activity and selectivity of the catalyst are reported in terms of half-wave potential and low H2O2 yield as determined by the rotating ring-disk electrode method. The significant electrochemical stability under accelerated durability test and high peak power density (787 mW cm−2) in H2-O2 PEMFC made these catalysts as potential candidates for efficient alternatives to PGMs in the fuel cell cathodes.

NdMn1.5Ru0.5O5, a high-performance electrocatalyst with low Ru content for acidic oxygen evolution reaction

A mixed oxide with the crystal structure of the DyMn2O5 family, namely NdMn1.5Ru0.5O5, is reported active for the oxygen evolution reaction (OER) in acidic media. NdMn1.5Ru0.5O5 displays high OER activity of 500 A gRu−1 at 1.5 V. Moreover, is more stable than most Ru oxides reported to date, remaining active for more than 500 cycles between 1.1. and 1.7 V at low scan rate of 10 mV s−1. The high activity and stability are attributed to the Ru cations, as NdMn2O5 exhibits very low OER activity. NdMn1.5Ru0.5O5 has particularly short Ru–Ru distances of 2.60 Å, a value close to the Ru–Ru metallic distances around 2.642 Å. The high activity and durability of NdMn1.5Ru0.5O5 for the OER are also demonstrated in a proton exchange membrane water electrolysis cell by producing a low-loaded anode electrode with 0.5 mgRucm−2. The cell achieves 1.97 V at 0.5 A cm−2, consistent with the performances reported for Ru-based catalysts but with lower Ru loading. This performance is maintained during 100 h of operation. Additionally, NdMn1.5Ru0.5O5 displays visible ORR activity in acidic media, recording an onset potential of 0.85 V at 0.1 mA cm−2. It is noteworthy to highlight the extreme rarity of bifunctional ORR/OER catalysts acidic media.

Enhancing electrocatalytic hydrogen evolution of MoS2 enabled by electrochemical cation implantation for simultaneous surface-defect and phase engineering

The increasing demand for energy-efficient and cost-effective water-splitting systems has prompted research on non-precious-metal-based electrocatalysts for the hydrogen evolution reaction (HER) over a wide pH range. Molybdenum sulfide (MoS2) has received considerable attention owing to its excellent HER activity in acidic media. However, its competitive HER properties must be improved to achieve better performance in alkaline or neutral environments. In this study, we introduced an electrochemical cation implantation (ECI) process as a versatile method to enhance the electrocatalytic properties of MoS2. By modifying the microstructure of MoS2, the ECI process induced vacancies in Mo and S, primarily in the basal planes and facilitated a gradual transition from the semiconducting (2H) to metallic (1T) phase. The optimized ECI-processed MoS2 catalysts exhibited improved HER activities and low overpotentials (η10, 144 mV) over the entire pH range compared with bare MoS2 catalysts, highlighting the potential application of the ECI process for enhanced electrocatalysts.

Superiority of CuSe as a non-nobel electrocatalyst among copper chalcogens for overall water splitting reactions

Among the transition metals copper is one of the cheapest earth- abandoned elements which can enhance electrocatalytic activity. The Cu-based catalysts are superior for catalytic performance and stability in alkaline media for oxygen evolution reaction (OER) and exhibit high activity in acidic media for hydrogen evolution reaction (HER).Synthesized CuSe nanoparticle is found as the most efficient bifunctional electrocatalyst among the synthesized Cu chalcogenides for water splitting reaction. Electrocatalytic performance for water oxidation was investigated in alkaline solution1(M) KOH for OER and 0.5 (M) H2SO4 for HER. To achieve 10 mA/cm2, it was observed an over potential (mV) of 343 for OER and 126 for HER, which are much smaller than these of CuS (385,320) and CuO (410, 345) studied. In this article, we have elucidated some essential criteria need to be specified to evaluate the water splitting performance including onset potential, overpotential, Tafel slope, turnover frequency (TOF), and stability of the copper chalcogenide nanoparticles.

Comparative study on various morphologies of WS2 for electrochemical hydrogen evolution reaction

Nowadays, the advancement of cost-effective and efficient electrocatalysts holds significant importance in facilitating the progress of high-performance electrochemical hydrogen evolution reaction (HER). Tungsten disulfides (WS2) are well recognized as highly promising electrocatalysts for HER due to their exceptional catalytic performance, outstanding stability, and comparatively affordable price. In this study, we used ammonium metatungstate hydrate and thioacetamide as precursors to fabricate WS2 nanoflowers (NFs) by hydrothermal method, whereas WS2-flakes were prepared from ammonium tetrathiotungstate through the thermolysis technique. These structures were evaluated for HER electrocatalytic activity in acidic media. The results revealed that WS2-NFs exhibit higher catalytic activity than WS2-flakes, with an overpotential of 325 mV to obtain a current density of 10 mA cm−2 and a Tafel slope of 92.3 mV dec−1. This performance was attributed to the larger electrochemically active surface area of WS2-NFs compared to WS2-flakes materials. The results of this study could bring the basis for further studies on the synthesis of WS2-based catalytic materials for HER. ® 2023 Journal of Science and Technology - NTTU

Efficient and robust IrW/WO3-x@NC/CP self-standing electrode with low Ir-loading for overall water electrolysis in acidic medium

To further enhance the long-term durability of the cost-effective Ir-based catalysts, some acid-stable oxides are used as supports for acidic OER catalysts. Herein, taking carbon paper (CP) as the substrate, we prepared a self-standing IrW/WO3-x@NC/CP electrode via a layer-by-layer modified method. Among it, N-doped porous C framework not only provides a large specific surface for the attachment of WO3-x, but also makes up for the lack of conductivity of WO3-x and accelerates the electron transport process. The interaction between Ir and W sites in the form of IrW alloy which has generated during the high-temperature calcination and the dispersed Ir in WO3-x matrix improve the intrinsic catalytic activity. And due to the Pt-like effect of W and the tuning role of the electronic structure by the IrW alloy, IrW/WO3-x@NC/CP with an Ir content of only 19.1 µg cm−2 exhibits excellent bifunctional activity in acidic media. To obtain 10 mA cm−2, IrW/WO3-x@NC/CP just needs overpotential of 22 mV (for HER) and 206 mV (for OER) respectively with a mass specific activity of 4.008 A mgIr−1 at 1.55 V. For the whole water splitting, it only requires 1.52 V and 1.70 V to reach 10 mA cm−2 and 100 mA cm−2 respectively, and can operate continuously for over 40 h.

Comparative study on various morphologies of WS2 for electrochemical hydrogen evolution reaction

Nowadays, the advancement of cost-effective and efficient electrocatalysts holds significant importance in facilitating the progress of high-performance electrochemical hydrogen evolution reaction (HER). Tungsten disulfides (WS2) are well recognized as highly promising electrocatalysts for HER due to their exceptional catalytic performance, outstanding stability, and comparatively affordable price. In this study, we used ammonium metatungstate hydrate and thioacetamide as precursors to fabricate WS2 nanoflowers (NFs) by hydrothermal method, whereas WS2-flakes were prepared from ammonium tetrathiotungstate through the thermolysis technique. These structures were evaluated for HER electrocatalytic activity in acidic media. The results revealed that WS2-NFs exhibit higher catalytic activity than WS2-flakes, with an overpotential of 325 mV to obtain a current density of 10 mA cm−2 and a Tafel slope of 92.3 mV dec−1. This performance was attributed to the larger electrochemically active surface area of WS2-NFs compared to WS2-flakes materials. The results of this study could bring the basis for further studies on the synthesis of WS2-based catalytic materials for HER.
 ® 2023 Journal of Science and Technology - NTTU

ВЕТЕРИНАРНО-САНИТАРНАЯ ХАРАКТЕРИСТИКА МЯСА БРОЙЛЕРОВ КРОССА «РОСС-308» ПРИ ВКЛЮЧЕНИИ В ИХ РАЦИОН МУЛЬТИЭНЗИМНОГО КОМПЛЕКСА

Veterinary and sanitary characteristics have been studied of foreign “Ross-308” cross broiler meat raised on the ration with multienzime protease complex with optimal activity in acid medium and xylanase with high degree of ther- mostability. It has been determined that metabolism changed in some of broilers and myopathy developed that is “white stripping”. This results in carcasses commercial qualities and meat qualities.

Carbon nanosheet-supported CrN nanoparticles as efficient and robust oxygen reduction electrocatalysts in acidic media and seawater Zn–air batteries

Carbon nanosheet-supported CrN nanoparticles render excellent ORR activity in acidic media and long-term stability in natural seawater Zn–air batteries.

Precisely constructing charge-asymmetric dual-atom Fe sites supported on hollow porous carbon spheres for efficient oxygen reduction

Transition group metal catalysts showing atomic dispersion are on the rise as affordable electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell batteries, but their activity in acidic media remains constrained.

Porous Tellurium-Doped Ruthenium Dioxide Nanotubes for Enhanced Acidic Water Oxidation.

Electrocatalysts with high activity and durability for acidic oxygen evolution reaction (OER) play a crucial role in achieving cost-effective hydrogen production via proton exchange membrane water electrolysis. A novel electrocatalyst, Te-doped RuO2 (Te-RuO2) nanotubes, synthesized using a template-directed process, which significantly enhances the OER performance in acidic media is reported. The Te-RuO2 nanotubes exhibit remarkable OER activity in acidic media, requiring an overpotential of only 171mV to achieve an anodic current density of 10mAcm-2. Furthermore, they maintain stable chronopotentiometric performance under 10mA cm-2 in acidic media for up to 50h. Based on the experimental results and density functional calculations, this significant improvement in OER performance to the synergistic effect of large specific surface area and modulated electronic structure resulting from the doping of Te cations is attributed.

The effect of additional nitrogen source on iron phthalocyanine-based nanocarbon catalysts for oxygen reduction reaction in acidic media

The focus in the development of catalysts doped with transition metals aims to replace platinum group metal catalysts in fuel cells. However, these non-precious metal catalysts exhibit limited performance in acidic environment for the oxygen reduction reaction (ORR) due to issues such as metal agglomeration and the subsequent loss of active sites. Herein, we synthesised catalysts doped with iron and nitrogen on a composite material consisting of carbide-derived carbon (CDC) and graphene (G), employing an additional nitrogen source dicyandiamide (DCDA), denoted as FeN-CDC/G/DCDA. Our physico-chemical analysis unveiled that the inclusion of DCDA was effective in mitigating metal agglomeration during the synthesis process and increasing the presence of Fe-Nx sites in the catalysts. Notably, the FeN-CDC/G/DCDA catalyst exhibited enhanced ORR activity in acid media with half-wave potential (E1/2) of 0.76 V, surpassing the performance of the FeN-CDC/G catalyst, which had an E1/2 value of 0.70 V. Furthermore, the rotating ring-disk electrode results indicated a reduced formation of hydrogen peroxide when employing the FeN-CDC/G/DCDA catalyst. The findings from this study represent a significant step towards the development of efficient catalysts for fuel cells, underscoring the pivotal role of additional nitrogen doping and its positive impact on the ORR performance.

Effects of Oxygen Defects in Zr Oxide-Based Thin Films on Oxygen Reduction Reaction in Acidic Media

Zirconium oxide thin films were prepared by RF magnetron sputtering as model catalysts for oxygen reduction reaction (ORR) in acidic media. The effects of sputtering conditions on ORR activity in acidic media was investigated. The effect of the deposition temperature on the ORR activity depended on whether the deposition atmosphere contained oxygen (Ar+O2, Ar+N2+O2) or only nitrogen (Ar+N2). In the range of 300-800 °C of the deposition temperature, the electrodes prepared in an Ar+N2 showed higher ORR activity. XRD and XPS results showed that the tetragonal phase grew in an Ar+N2 atmosphere, while a mixed phase of tetragonal and monoclinic phases grew in an Ar+O2 atmosphere. It was found that Zr oxide thin film with a high proportion of tetragonal phase showed high ORR activity.

A facile synthesis of Bi2O3/SnS2 and Ag@Bi2O3/SnS2 nanostructures and their enhanced photodegradation application toward RhB

In this study, the binary Bi2O3/SnS2 (2 & 4 wt%) and ternary Ag (2, 4 & 6 wt%)@Bi2O3/SnS2 (2 wt%) nanostructures were prepared by the facile precipitation and deposition method. The synthesized materials were characterized by using several analytical methods such as X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray, ultraviolet visible diffuse reflectance specctroscopy, photoluminescence, and X-ray photoelectron spectroscopy. The organic pollutant Rhodamine B (RhB) was used to determine the photocatalytic efficiency of prepared nanocomposites. Bi2O3/SnS2 and Ag@Bi2O3/SnS2 nanocomposites showed the maximum photocatalytic activity in acidic medium. As photocatalyst, ternary nanocomposite Ag (4 wt%)@Bi2O3/SnS2 (2 wt%) exhibited admirable performance (99.85% degradation in 40 min) in comparison to binary Bi2O3/SnS2 (2 wt%) nanocomposite for the degradation of RhB (98.95% degradation in 40 min). The enhanced activity was ascribed to the fabrication of Z-type heterojunctions which are beneficial for the effective separation of photoinduced charged species and decrease the recombination rate of charge carrier species. Also, the Ag (4 wt%) @ Bi2O3/SnS2 (2 wt%) photocatalyst showed magnificent stability after five cycles, in which the efficiency dropped by 5.31% only. The role of scavengers involved during the degradation reaction was conducted, and from this experimentation, the superoxide anion radicals and holes are found responsible dominant active species for the RhB degradation. This research work highlights the enhanced photocatalytic abilities and performance ofAg@Bi2O3/SnS2 for the elimination of organic pollutants such as RhB dye and it would exhibit the potential application in wastewater treatment.

Hierarchically Porous Carbons with Highly Curved Surfaces for Hosting Single Metal FeN4 Sites as Outstanding Oxygen Reduction Catalysts.

Iron-nitrogen-carbon (FeNC) materials have emerged as a promising alternative to platinum-group metals for catalyzing the oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells. However, their low intrinsic activity and stability are major impediments. Herein, an FeN-C electrocatalyst with dense FeN4 sites on hierarchically porous carbons with highly curved surfaces (denoted as FeN4 -hcC) is reported. The FeN4 -hcC catalyst displays exceptional ORR activity in acidic media, with a high half-wave potential of 0.85V (versus reversible hydrogen electrode) in 0.5m H2 SO4 . When integrated into a membrane electrode assembly, the corresponding cathode displays a high maximum peak power density of 0.592W cm-2 and demonstrates operating durability over 30000 cycles under harsh H2 /air conditions, outperforming previously reported Fe-NC electrocatalysts. These experimental and theoretical studies suggest that the curved carbon support fine-tunes the local coordination environment, lowers the energies of the Fe d-band centers, and inhibits the adsorption of oxygenated species, which can enhance the ORR activity and stability. This work provides new insight into the carbon nanostructure-activity correlation for ORR catalysis. It also offers a new approach to designing advanced single-metal-site catalysts for energy-conversion applications.