Retention Of Catalytic Activity Research Articles

Aliphatic Ketone Claisen Rearrangement: Troubleshooting the Transetherification Step by Identifying a Stable Acid Catalyst.

After optimization for retention of catalytic activity, 4-chlorobenzoic acid emerged as the optimal catalyst for the aliphatic ketone Claisen rearrangement. The optimal catalyst enables a one-pot, metal-free, catalytic protocol from allylic alcohols to γ,δ-unsaturated ketones. The optimized process tolerates a range of substrates, including substituents with acid-labile protecting groups. Reaction monitoring and DFT studies of the aliphatic ketone Claisen process agree that the ultimate rearrangement step typically has the highest activation barrier.

Nickel and Molybdenum Composites Decorated Nitrogen-Doped Carbon Catalysts from Spent Coffee Grounds for Alkaline Hydrogen Evolution.

Biomass-derived materials can help develop efficient, environmentally friendly and cost-effective catalysts, thereby improving the sustainability of hydrogen production. Herein, we propose a simple method to produce nickel and molybdenum composites decorated spent coffee grounds (SCG) as an efficient catalyst, SCG(200)@NiMo, for electrocatalytic hydrogen production. The porous carbon supporter derived form SCG provided a larger surface, prevented aggregation during the high temperature pyrolysis, optimized the electronic structure by N and provided a reducing atmosphere for the oxides reduction to form heterojunctions. The sieved SCG showed obvious improvement of HER performance and enhanced conductivity and long-term durability. The obtained SCG(200)@NiMo exhibits the highest electrochemical performance for the hydrogen evolution reaction process, as evidenced by the overpotential of only 127 mV at a current density of ɳ10 and 97.7 % catalytic activity retention even after 12 h of operation. This work may stimulate further exploration of efficient electrocatalysts derived from biomass.

Boronic acid functionalized silica‐coated Fe3O4 as a novel magnetically separable catalyst for the synthesis of hydrazinyl thiazoles

A novel silica‐coated magnetite supported boronic acid functionalized nanocatalyst (Fe3O4@SiO2‐Pr‐N=CH‐C6H4B[OH]2) was synthesized using a simple synthetic protocol. The catalyst was fully characterized by using Fourier transform‐infrared (FT‐IR), X‐ray diffraction (XRD), energy dispersive X‐ray (EDX), thermogravimetric analysis‐differential thermal analysis (TGA‐DTA), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM) techniques. The structural investigations revealed that the catalyst is nano‐sized (average crystallite size 13 nm), spherical, thermally stable, and magnetic in nature having a magnetic saturation of 51.26 emu/g. The catalytic activity of Fe3O4@SiO2‐Pr‐N=CH‐C6H4B(OH)2 was explored in the synthesis of hydrazinyl thiazoles via one‐pot, three‐component reaction of phenacyl halide, thiosemicarbazide and aryl aldehyde in EtOH:H2O (50:50, v/v) at room temperature and it gave above 90% yields of hydrazinyl thiazoles. The catalyst being magnetically separable can be reused six times with the retention of catalytic activity. The present approach offers the advantages of operational simplicity, shorter reaction time, ambient reaction condition, facile separation of catalyst, and higher yields of the products.

Biomimetic Metal-Pyrimidine Nanoflowers: Enzyme Immobilization Platforms with Boosted Activity.

For the enzyme immobilization platform, enhancing enzyme activity retention while improving enzyme stability remains a challenge for sensitive sensing analysis. Herein, an in situ biomimetic immobilized enzyme carrier (metal-pyrimidine nanoflowers, MPNFs) synthesized by the coordination of DNA base derivative (2-aminopyrimidine) with Zn2+ in the aqueous phase at room temperature is developed. The biocompatibility of 2-aminopyrimidine and the hydrophilicity and green synthetic conditions of MPNFs allows the immobilized enzymes to retain above 91.2% catalytic activity. On this basis, a cascade catalytic platform is constructed by simultaneously immobilizing acetylcholinesterase (AChE), choline oxidase (CHO), and horseradish peroxidase (HRP) in MPNFs (AChE/CHO/HRP@MPNFs) for organophosphorus pesticides (OPs) colorimetric biosensing detection. The assay could specifically detect parathion-methyl within 13min with a wider linear range (0.1-1000.0nm) and a lower limit of detection (LOD) (0.032nm). The remarkable stability of the immobilized enzymes is also achieved under harsh environments, room temperature storage, and recycling. Furthermore, a portable and cost-effective biosensing platform is developed by integrating AChE/CHO/HRP@MPNFs with a smartphone-assisted paper device for the on-site detection of OPs. Overall, the high catalytic activity retention and the enhanced detection performance demonstrate that MPNF is a robust carrier in enzyme immobilization and holds great promise in biosensing and other field applications.

Cr(III)-complex tethered lacunary polyoxometalate as an efficient electrocatalyst for hydrogen evolution reaction in aqueous media

A lacunary polyoxometalate-based hybrid material, wherein Cr (acac)3 complex is covalently tethered through aminopropyltrimethoxysilyl groups to a Keggin-type lacunary phosphomolybdate anion, [PMo11O39]7-, is reported as a new heterogeneous electrocatalyst for the efficient electrocatalytic hydrogen evolution process. Physicochemical characterization techniques, like FT-IR spectroscopy, X-ray diffraction (XRD), and energy dispersive X-ray (EDX) analyses confirmed the successful functionalization and synthesis of desired material. The prepared hybrid material revealed eminent hydrogen evolution activity with a low overpotential of 330 mV to attain a 10 mA cm−2 current density and a Tafel slope of 150 mV.dec−1. Additionally, it also exhibited outstanding electrochemical stability in H2SO4 (0.5 M) over 8 h and catalytic activity retention even after 2000 catalytic cycles. This work introduces an appropriate procedure for preparing inexpensive and highly active electrocatalysts for replacing precious Pt counterparts in hydrogen evolution process.

Immobilization of α-galactosidase in polyvinyl alcohol-chitosan-glycidyl methacrylate hydrogels based on directional freezing-assisted salting-out strategy for hydrolysis of RFOs

Raffinose family oligosaccharides (RFOs) in food are the main factors causing flatulence in Irritable Bowel Syndrome (IBS) patients and the development of effective approaches for reducing food-derived RFOs is of paramount importance. In this study, polyvinyl alcohol (PVA)-chitosan (CS)-glycidyl methacrylate (GMA) immobilized α-galactosidase was prepared by the directional freezing-assisted salting-out technique, aimed to hydrolyze RFOs. SEM, FTIR, XPS, fluorescence and UV characterization results demonstrated that α-galactosidase was successfully cross-linked in the PVA-CS-GMA hydrogels, forming a distinct porous stable network through the covalent bond between the enzyme and the carrier. Mechanical performance and swelling capacity analysis illustrated that α-gal @ PVA-CS-GMA not only had suitable strength and toughness for longer durability, but also exhibited high water content and swelling capacity for better retention of catalytic activity. The enzymatic properties of α-gal @ PVA-CS-GMA showed an improved Km value, pH and temperature tolerance range, anti-enzymatic inhibitor (melibiose) activity compared to the free α-galactosidase and its reusability was at least 12 times with prolonged storage stability. Finally, it was successfully applied in the hydrolysis of RFOs in soybeans. These findings provide a new strategy for the development of α-galactosidase immobilization system to biological transform the RFOs components in the food for diet intervention of IBS.

Water-Soluble Ionic Metal-Organic Polyhedra as a Versatile Platform for Enzyme Bio-immobilization.

Metal-organic polyhedra (MOPs) can act as elementary structural units for the design of modular porous materials; however, their association with biological systems remains greatly restricted by their typically low stabilities and solubilities in water. Herein, we describe the preparation of novel MOPs bearing either anionic or cationic groups and exhibiting a high affinity for proteins. Simple mixing of the protein bovine serum albumin (BSA) and ionic MOP aqueous solutions resulted in the spontaneous formation of MOP-protein assemblies, in a colloidal state or as solid precipitates depending on the initial mixing ratio. The versatility of the method was further illustrated using two enzymes, catalase and cytochrome c, with different sizes and isoelectric points (pI's) below and above 7. This mode of assembly led to the high retention of catalytic activity and enabled recyclability. Furthermore, the co-immobilization of cytochrome c with highly charged MOPs resulted in a substantial 44-fold increase of its catalytic activity.

Framework for Optimizing Polymeric Supports for Immobilized Biocatalysts by Computational Analysis of Enzyme Surface Hydrophobicity

Immobilization is a powerful strategy for improving enzyme usability and stability in various technologies that employ biocatalysis. However, the interactions leading to stabilization or destabilization remain poorly understood, and a support that may stabilize one enzyme may destabilize another. Employing chemically heterogeneous and complex random copolymer brushes as supports, we demonstrate a rational approach toward estimating the chemical composition of an optimally stabilizing enzyme immobilization support by computational analysis of enzyme surface hydrophobicity. This approach was tested by immobilizing a range of enzymes with diverse functions and hydrophobicity on tunable statistical random copolymer brush supports composed of poly(ethylene glycol) methacrylate (PEGMA) and sulfobetaine methacrylate (SBMA). Remarkably, we observed greatly improved enzyme performance as a function of brush composition with enhancements in the retention of catalytic activity at temperatures as high as 90 °C. Additionally, we observed an increase in activity at the optimal temperature by as much as 20-fold relative to the activity at the optimal temperature of the unimmobilized form of the enzyme. Most significantly, our results showed that the optimal composition of the brush support correlated with the overall hydrophobicity of the enzyme surface (ΔGsolv,total/area), which was determined from computational analysis. This correlation provides a framework for the choice of polymer brush supports based on enzyme structure and stabilizing enzymes using complex synthetic materials.

Preparation of hyperbranched 4-dimethylaminopyridine catalyst for the efficient synthesis of vitamin E succinate

Sorbitol was employed as the grafting agent to modify nano-silica by the hyperbranched reaction. The obtained carrier was further used to prepare immobilized 4-dimethylaminopyridine (DMAP), which was successfully applied to produce vitamin E succinate. Two crucial steps were systematically investigated during the preparation of hyperbranched loaded DMAP: the epoxy-alcohol addition and N-alkylation reactions. For the epoxy-alcohol addition reaction, the maximum hydroxyl content reached 8.89 mmol/g when the molar ratio of sorbitol to epoxide was 2.5:1, the reaction temperature was 55 °C, the stirring rate was 500 rpm, and the reaction time was 8 h. In the N-alkylation reaction, when the reaction time was 20 h, the reaction temperature was 130 °C, the molar ratio of MAP to K 2 CO 3 was 1:1.5, the KI to MAP molar ratio was 1:1 and the stirring rate was 600 rpm, the highest loading of DMAP reached 5.17 mmol/g. The catalytic performance of the loaded DMAP with different branching levels was evaluated by the acetylation reaction. The highest catalytic activity was observed in the hyperbranched catalyst, which reached 24.97 mmol/h·g. Moreover, the stability of the prepared immobilized DMAP was significantly enhanced. After being used for ten batches, 94.9% of the catalytic activity retention rate was obtained.

Highly CO-selective Ni–MgO–CexZr1–xO2 catalyst for efficient low-temperature reverse water–gas shift reaction

High inertness of CO2 hinders its usage as a cost-effective C1 resource to produce value-added chemicals, and hence, reactive H2 are often employed for CO2 utilization. CO is a more reactive C1 building block that can be produced via the reverse water–gas shift (RWGS) reaction using CO2, but this requires a high temperature with robust catalysts that should endure the harsh endothermic conditions. Herein, Ni–MgO–CexZr1–xO2 (NMCxZ1–xO) catalysts with various Ce/Zr ratios, giving different strong metal–support interaction (SMSI) among metallic components, are investigated for low-temperature RWGS reaction to achieve high CO selectivity. The control of Ce/Zr ratios affords systematic changes in the oxygen storage capacity (OSC), acidity, and basicity, affording remarkable changes in the catalytic behaviors for CO2 conversion and CO selectivity. Among various NMCxZ1-xO catalysts, NMC0.6Z0.4O exhibited the highest resistance to change in reaction temperature, maintaining 100 % CO selectivity below 320 °C, whereas the CO2 conversion and CH4 selectivity of the other catalysts increased dramatically with increasing reaction temperature. The 100 % CO selectivity can be attributed to the high OSC and optimized balance of acidity and basicity of the NMC0.6Z0.4O catalyst, and its retention of catalytic activity owing to the SMSI among metallic components.

Solid Lewis acid-base pair catalysts constructed by regulations on defects of UiO-66 for the catalytic hydrogenation of cinnamaldehyde

A series of highly-defective UiO-66 were synthesized and utilized as catalyst in the hydrogenation of cinnamaldehyde (CALD) to cinnamylalcohol (CALH) in isopropanol. The physico-chemical properties of the catalysts were characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis and N2 adsorption-desorption. It was found that there are two kinds of atomic Lewis acid-base pairs existing in the defective UiO-66, exactly Zr4+-O2- and Zr4+-OH-, which are active sites for CALD hydrogenation to form CALH. UiO-66–0.3 with the most defects shows a much higher reaction rate constant, which is 5.5 times that of UiO-66–2.0, and gives the best CALD conversion of 85.5% and CALH selectivity of 94.0% at 140 ℃ after 3 h. The acid-base synergistic catalysis mechanism was proposed. Moreover, the defective UiO-66 showed good recyclability for up to 7 cycles with retention of catalytic activity as well as structural stability.

Dicationic Ionic Liquid Modified Chitosan as a Sustainable Heterogeneous Catalyst for Knoevenagel Condensation Reactions

Ionic liquid (IL) grafted chitosan (CS) is fabricated in a feasible three-step process and used as a catalyst for the Knoevenagel condensation reaction. The IL modified CS (IL-CS) shows higher conversion/yield compared to pristine CS and Pyridine modified CS (Py-CS). The better efficiency of IL-CS can be ascribed to the synergistic effect of H-bonding groups (–OH of CS) and quaternary ammonium groups of ionic liquid. The material is very efficient in converting various functionalized aromatic aldehydes into their benzylidenemalononitrile derivatives. In addition, the catalyst exhibits retention of catalytic activity up to five cycles in the reusability study. The characterization of the recycled material clearly indicates the robust nature of IL-CS. Our work provides a feasible approach towards sustainable catalyst construction for industrially important reactions.

Design and application of a polyoxometalate-ionic liquid-graphene oxide hybrid nanomaterial: New electrocatalyst for water oxidation

Design of a new hybrid nanomaterial, CoW12−IL−GO, is reported for utilization as an electrocatalyst for water oxidation reaction for oxygen evolution at neutral pH conditions. The desired electrocatalyst was prepared by covalent attachment of ionic liquid (IL) species to graphene oxide for preparing IL−GO and then electrostatic interaction of supported imidazolium cations with Keggin type [CoW12O40]6- polyanions. After confirming the construction of CoW12−IL−GO with different physicochemical techniques, its electrochemical properties was evaluated. The CoW12 −IL−GO exhibited a low onset potential of 1.3 V vs. NHE and low overpotential of 269 mV at 10 mA.cm−2 with a low Tafel slope of 92 mV.dec−1 at neutral pH. Eventually, the electrocatalytic activity of prepared CoW12−IL−GO was studied in water oxidation reaction which revealed its outstanding stability over 14 h and retention of catalytic activity even after 900 catalytic cycles.

Metal-Free Triazine-Based 2D Covalent Organic Framework for Efficient H2 Evolution by Electrochemical Water Splitting.

Hydrogen evolution reaction (HER) by electrochemical water splitting is one of the most active areas of energy research, yet the benchmark electrocatalysts used for this reaction are based on expensive noble metals. This is a major bottleneck for their large-scale operation. Thus, development of efficient metal-free electrocatalysts is of paramount importance for sustainable and economical production of the renewable fuel hydrogen by water splitting. Covalent organic frameworks (COFs) show much promise for this application by virtue of their architectural stability, nanoporosity, abundant active sites located periodically throughout the framework, and high electronic conductivity due to extended π-delocalization. This study concerns a new COF material, C6 -TRZ-TFP, which is synthesized by solvothermal polycondensation of 2-hydroxybenzene-1,3,5-tricarbaldehyde (TFP) and 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris[(1,1'-biphenyl)-4-amine]. C6 -TRZ-TFP displayed excellent HER activity in electrochemical water splitting, with a very low overpotential of 200 mV and specific activity of 0.2831 mA cm-2 together with high retention of catalytic activity after a long duration of electrocatalysis in 0.5 m aqueous H2 SO4 . Density functional theory calculations suggest that the electron-deficient carbon sites near the π electron-donating nitrogen atoms are more active towards HER than those near the electron-withdrawing nitrogen and oxygen atoms.

Tailor-made novel electrospun polystyrene/poly(d,l-lactide-co-glycolide) for oxidoreductases immobilization: Improvement of catalytic properties under extreme reaction conditions

Immobilized enzymes find applications in many areas such as pharmacy, medicine, food production and environmental protection. However, protecting these biocatalysts against harsh reaction conditions and retaining their enzymatic activity even after several biocatalytic cycles are major challenges. Properly selected supports and type of surface modifier therefore seem to be crucial for achieving high retention of catalytic activity of immobilized biomolecules. Here we propose production of novel composite electrospun fibers from polystyrene/poly(d,l-lactide-co-glycolide) (PS/PDLG) and its application as a support for immobilization of oxidoreductases such as alcohol dehydrogenase (ADH) and laccase (LAC). Two strategies of covalent binding, (i) (3-aminopropyl)triethoxysilane (APTES) with glutaraldehyde (GA) and (ii) polydopamine (PDA), were applied to attach oxidoreductases to PS/PDLG. The average fiber diameter was shown to increase from 1.252 µm to even 3.367 µm after enzyme immobilization. Effective production of PS/PDLG fibers and biomolecule attachment were confirmed by Fourier transform infrared spectroscopy analysis. The highest substrate conversion efficiency was observed at pH 6.5 and 5 for ADH and LAC, respectively, and at 25 °C for enzymes attached using the APTES + GA approach. Improvement of enzyme stabilization at high temperatures was confirmed in that relative activities of enzymes immobilized onto PS/PDLG fibers were over 20% higher than those of the free biomolecules, and enzyme leaching from the support using acetate and MES buffers was below 10 mg/g.

Magnesium ferrichromate nanoparticles: an efficient and recyclable catalyst in the synthesis of pyrano[2,3-c]pyrazole derivatives

Magnetically separable magnesium ferrichromate nanoparticles (MgFeCrO4 NPs) were synthesized by aqueous combustion synthesis (ACS) using glycine as the fuel. The as-synthesized powder was characterized using XRD, FTIR, SEM–EDX and SQUID techniques. Rietveld refinement studies inferred the single-phase cubic structure of the nanoferrite. Using Williamson–Hall plot, the lattice strain and the crystallite size were evaluated. Small value of lattice strain is indicative of absence of strain in the crystal lattice. The M–O bonding at the tetrahedral as well as the octahedral position was confirmed by FTIR Spectroscopy. Morphological investigations demonstrated sphere-like nanostructures with 50–100 nm particle size using SEM. Absence of any impurity in the EDX spectrum suggests formation of extremely pure MgFeCrO4 NPs. The room temperature magnetization was studied using vibrating sample magnetometer, and the nanoferrite exhibits superparamagnetic behaviour. The pyrano[2,3-c]pyrazole derivatives were synthesized in water/ethanol solvent system using MgFeCrO4 NPs heterogenous catalyst. A very short reaction time, maximum yield, easy method of separation of product and environmentally safer and milder reaction conditions are some of the advantages of our work along with the retention of catalytic activity up to five cycles. Synthesis of chromene derivatives using magnetically separable magnesium ferrichromate (MgFeCrO4).

Modified ultradispersed diamonds based catalytic systems in cross-coupling reactions

Methods for preparation of nanocomposites of modified detonation nanodiamonds (DND) with metallic palladium have been developed and their catalytic activity in the Suzuki-Miyaura cross-coupling reaction in various reaction media has been studied. Methods for the regeneration of palladium-containing nanocomposites from the reaction mixture have been developed. The high catalytic activity of nanocomposites is confirmed by kinetic analysis based on the results of chromatographic analysis of the reaction mixture and is comparable to the literature data about similar catalytic systems. Regenerated nanocomposites showed the retention of catalytic activity for 3 consecutive cross-coupling cycles on model systems.

Microemulsion‐Based Gels for Lipase‐Catalyzed Ester Synthesis in Organic Solvents

AbstractMicroemulsions are clear, stable, isotropic mixtures of oil, water, and surfactant, frequently in combination with a cosurfactant. These systems are currently of interest to the pharmaceutical scientist because of their considerable potential to act as drug delivery vehicles by incorporating a wide range of drug molecules. The purpose of this work is to solubilize in AOT [sodium bis(2‐ethylhexyl)sulphosuccinate] water‐in‐oil microemulsions at two different R‐values the Chromobacterium viscosum (CV) lipase and lipoprotein lipase ex Pseudomonas and to use them to catalyze the lactonization of 16‐hydroxyhexadecanoic acid at 40°C. CV lipase is also immobilized in gelatin‐containing microemulsion‐based gels (MBGs) with retention of catalytic activity. These lipase‐containing MBGs proved to be novel solid‐phase catalysts for use in apolar organic solvents. CV lipase‐containing MBGs are used to synthesize, on a preparative scale, a variety of different esters under mild conditions.

AuCo3O4/C – Different Fabrication Methods and Application for Fuel Cell Reactions

Nanoscale materials are very important in many industries. There are many various synthesis methods such as adsorption, electroless deposition, galvanic displacement or microwave irradiation methods which let to fabricate nanomaterials. Lately, microwave irradiation is used as a rapid convenient method which gives excellent yields and higher purity of the products than conventional methods. Nanoparticles-based catalysts are usually heterogeneous catalysts broken up into metal nanoparticles in order to speed up the catalytic process. Metal nanoparticles have a higher surface area so there is increased catalytic activity because more catalytic reactions can occur at the same time. Nanoparticles catalysts can also be easily separated and recycled with more retention of catalytic activity than their bulk counterparts. Nanoparticles of gold are attractive for their interaction with other compounds and property to attract catalytic active groups.In this work, we investigated the influence of synthesis method to the electrocatalytic activity of catalyst. Therefore, Au nanoparticles were deposited on the Co3O4/carbon (Co3O4/C) substrate using microwave irradiation AuCo3O4/C-1, AuCo3O4/C-2 and impregnation AuCo3O4/C-3 methods. The composition, morphology and structure of the prepared catalysts were characterized using Inductively Coupled Plasma Optical Emission Spectroscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy and X-ray diffraction. The electrocatalytic properties of prepared catalysts were investigated towards ethylene glycol electro-oxidation and oxygen electro-reduction reactions in an alkaline medium. Electrochemical analysis was performed using a rotating disc electrode and the Autolab electrochemical workstation.It has been determined, that in all cases modification of Co3O4/C catalyst by gold improved the electrocatalytic properties of synthesized AuCo3O4/C catalysts. As-prepared AuCo3O4/C catalysts showed an enhanced electrocatalytic activity towards the electro-oxidation of ethylene glycol and electro-reduction of oxygen in an alkaline medium compared with that obtained for the Co3O4/C or Au/C catalysts. The AuCo3O4/C catalysts prepared by microwave irradiation heating demonstrated up to 3 times higher electrocatalytic activity towards the electro-oxidation of ethylene glycol and up to 2 fold higher electrocatalytic activity towards electro-reduction of oxygen compared with that of the AuCo3O4/C catalyst prepared using impregnation.

Electrodeposited Bimetallic (PtPd, PtRu, PtSn) Catalysts on Titanium Support for Methanol Oxidation in Direct Methanol Fuel Cells

The electrodeposition of platinum-based catalysts (PtPd, PtRu, and PtSn) using the pulse current deposition technique was carried out on titanium substrate to prepare electrodes of different compositions to identify a possible catalyst offering high catalytic activity towards methanol oxidation (MOR). Characterization by XRD, SEM, and EDX confirmed the deposition of catalysts with the desired composition with various morphologies of dendritic, spherical, and irregular deposits for PtPd, PtRu, and PtSn, respectively. Among the various compositions and binary metals studied, electrochemical results indicate PtRu/Ti with Pt to Ru ratio of 1:1 (Pt50Ru50/Ti) to be most active with lower onset potentials for CO oxidation (0.381 V) and methanol oxidation (0.545 V) along with higher peak current density of ∼90 mA cm−2 compared to Pt/Ti (with onset potentials of 0.601 V for CO oxidation, 0.659 V for methanol oxidation and ∼68 mA cm−2 peak current density). Moreover, the MOR catalytic activity retention after 1000 accelerated durability test cycles was the highest for Pt50Ru50/Ti at 55% compared to Pt/Ti and commercial Pt/C.