High Electrochemical Active Surface Area Research Articles

MnCo2O4 Spinel & Carbon Black coated Nickel Foam Electrode. A Bifunctional Water-Splitting Catalyst?

Hydrogen has the potential to revolutionise how we produce and consume energy. We can meet energy demands without compromising the environment by using renewable sources such as wind, solar and wave power producing low-cost electricity to split the water molecule into its constituent parts. We could then convert Hydrogen back to electricity using a fuel cell, as illustrated in Figure 1. The by-product in this entire process is water, giving a clean technology with no toxic or greenhouses gases. Currently the best performing electrocatalytic materials for water splitting are noble metal based, namely platinum for the hydrogen evolution reaction (HER) and Ruthenium for the oxygen evolution reaction (OER). The use of these materials is unsustainable and makes fuel cells too expensive for commercial applications. We must engineer sustainable, cost-effective alternatives.Nickel foam electrodes display desirable electrocatalytic properties such as a large surface area compared to volume with highly conducting, porous networks, while transition metal dichalcogenides show very good electronic properties with high surface areas and large active sites. In this work we show that it is possible to electrochemically and solvothermally produce CoSex and CoSex composites on a porous nickel foam electrode (NFE). The best performing materials were selected and evaluated via electrochemical impedance spectroscopy. This analysis showed high electrochemical active surface area (ECSA) values and good stability across the selected materials. Scanning electron microscopy (SEM) images reveal that the surfaces of the synthesized materials exhibit distinct morphologies and have been significantly modified. Further electrochemical evaluation of the materials reveals low overpotentials for both hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) thus showing promise as a potential bi-functional electrocatalyst in overall water splitting.References(1) Chaudhari, N. K.; Jin, H.; Kim, B.; Lee, K. Nanostructured Materials on 3D Nickel Foam as Electrocatalysts for Water Splitting. Nanoscale. 2017. https://doi.org/10.1039/c7nr04187j.(2) Minadakis, M. P.; Tagmatarchis, N. Exfoliated Transition Metal Dichalcogenide-Based Electrocatalysts for Oxygen Evolution Reaction. Advanced Sustainable Systems. 2023. https://doi.org/10.1002/adsu.202300193.(3) Sukanya, R.; da Silva Alves, D. C.; Breslin, C. B. Review—Recent Developments in the Applications of 2D Transition Metal Dichalcogenides as Electrocatalysts in the Generation of Hydrogen for Renewable Energy Conversion. J Electrochem Soc 2022, 169 (6). https://doi.org/10.1149/1945-7111/ac7172. Figure 1

Platinum-Ruthenium Bimetallic Nanoparticle Catalysts Synthesized Via Direct Joule Heating for Methanol Fuel Cells.

Platinum-Ruthenium (PtRu) bimetallic nanoparticles are promising catalysts for methanol oxidation reaction (MOR) required by direct methanol fuel cells. However, existing catalyst synthesis methods have difficulty controlling their composition and structures. Here, a direct Joule heating method to yield highly active and stable PtRu catalysts for MOR is shown. The optimized Joule heating condition at 1000°C over 50 microseconds produces uniform PtRu nanoparticles (6.32wt.% Pt and 2.97 wt% Ru) with an average size of 2.0 ± 0.5 nanometers supported on carbon black substrates. They have a large electrochemically active surface area (ECSA) of 239 m2 g-1 and a high ECSA normalized specific activity of 0.295mA cm-2. They demonstrate a peak mass activity of 705.9mA mgPt -1 for MOR, 2.8 times that of commercial 20 wt.% platinum/carbon catalysts, and much superior to PtRu catalysts obtained by standard hydrothermal synthesis. Theoretical calculation results indicate that the superior catalytic activity can be attributed to modified Pt sites in PtRu nanoparticles, enabling strong methanol adsorption and weak carbon monoxide binding. Further, the PtRu catalyst demonstrates excellent stability in two-electrode methanol fuel cell tests with 85.3% current density retention and minimum Pt surface oxidation after 24 h.

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.

Unravelling the efficacy of pencil graphite anode decorated with PdCu@γ-Fe2O3 nanoparticles in the electro-oxidation of amoxicillin: Insights into kinetics, oxidative pathways and toxicity evaluation

Indiscriminate use of antibiotics has resulted in the occurrence of antibiotic residues in sediments, water bodies and industrial sewage, causing ill effects on aquatic organisms and humans. Electrochemical oxidation process via in-situ generation of strong oxidant •OH is the promising method for the removal of pollutants. In this work, PdCu/γ-Fe2O3 NPs electrodeposited pencil graphite electrode (PdCu/γ-Fe2O3@PGE) has been projected as a cost-effective anode for electro-oxidation of amoxicillin (AMX), while bare PGE was used as a cathode to generate H2O2. The electrochemical measurements showed that PdCu/γ-Fe2O3 @PGE exhibited lower ΔEp (0.191 V), high electrochemical active surface area (ECSA) (0.4620 cm2), higher oxygen evolution potential (OEP) (1.72 V), and lower charge transfer resistance of 9.747 Ω/ cm2 which was ideal for electro-oxidation of AMX. Under the optimum reaction conditions (I = 0.2 mA, pH = 4), the % AMX removal reached 90.5 % after 50 min of electro-oxidation in 0.5 M NaCl. •OH, H2O2, and HOCl were found to be the in-situ generated oxidants. The AMX solution after electro-oxidation did not exhibit antibacterial activity. The toxicity of the formed intermediates were evaluated using Toxicity Estimation Software Tool (T.E.S.T) and found to be less toxic. The electrical energy consumption was estimated to be 0.786 kWhm−3.Thus, modified PGE finds application in the remediation of effluents containing amoxicillin.

Greenly Synthesized CoPBA@PANI as a Proficient Electrocatalyst for Oxygen Evolution Reaction and Its Green Sustainability Assessments.

Water electrolysis is a key factor to generate mobile and sustainable energy sources for H2 production. Cobalt-based Prussian Blue analogues encompassed with polymer support electrocatalysts CoPBAX@PANI (CoPBA@PANI-100, CoPBA@PANI-200, and CoPBA@PANI-300) have been synthesized and characterized. The well-designed CoPBA@PANI-200/GC shows a low overpotential (η10) of 301 mV with a small Tafel slope (56 mV dec-1), comapred to that of IrO2 (348 mV ; 98 mV dec-1) for OER. The conductivity with stability of CoPBAX@PANI have been increased due to the synergistic effect of CoPBA with PANI. PANI provides additional active sites and shows strong binding with Co ions, and the even distribution of CoPBA overcomes the sluggish kinetics. The turnover frequency (TOF) of CoPBA@PANI-200/GC (0.0212, s-1) was ∼15 times higher than IrO2 (0.0014 s-1) at 1.60 V. Furthermore, CoPBA@PANI-200/NF delivers low overpotential of 274 mV@10 mA cm-2 and exhibits a durability of >250 h with a potential loss of 4.2%. Benefiting from strong electronic interaction between polymer support and evenly distributed CoPBA, CoPBAx@PANI shows higher electrochemical active surface area (ECSA) of 53.08 mF cm-2. The solar-based water electrolysis confirmed the practical use of CoPBA@PANI-200/NF (1.57 V) for eco-benign industrial H2 production. The CoPBA@PANI-200 shows exceptional OER performances as well as favorable kinetics to resolve the sluggish water oxidation. Hence, the cost-effective CoPBA@PANI performances opens a prospective way to boost the efficiency of other cobalt-derived catalysts in renewable energy devices.

Defect-rich cypress-leaf-like Cu2+1O@NiF for high-performance non-invasive glucose detection with low detection limit

Non-invasive detection of body fluid glucose concentration is of great significance in the diagnosis and treatment of diabetes, which poses a new challenge to the reduction of the detection limit of glucose sensors. In this work, a novel non-enzymatic glucose sensor (defect-rich cypress-leaf-like Cu2+1O@NiF) was proposed by rapid electrodeposition of cypress-leaf-like Cu2+1O on the surface of nickel foam (NiF) substrate. Due to the high electrochemical active surface area and abundant defects of cypress-leaf-like Cu2+1O providing more catalytic active sites, the prepared non-enzymatic sensor has an ultra-low detection limit (0.9 nM), high sensitivity (88,419.4 μA∙mM−1∙cm−2 (1 nM-0.5 μM) and 2095.5 μA∙mM−1∙cm−2 (1 μM-4.33 mM)) and wide linear range (1 nM-4.33 mM) with good selectivity, reproducibility and stability. Furthermore, the obtained sensors exhibited high detection stability, accuracy and recovery for glucose detection of human body fluid samples, which means that the defect-rich cypress-leaf-like Cu2+1O@NiF electrode is an ideal candidate for non-invasive glucose sensors.

Engineering 1T-MoS2 core-shells unified with nitrogen-rich amorphous carbon nanotube for ratiometric low-level detection of nitroquinoline

Nitroquinolines are an important toxic element in ecosystems and have great significance for monitoring the environmental system with appropriate tools for safety assessments. In this work, we developed a sensitive method for accurate and low-level detection of 5-nitroquinoline (5-NQ) using 1T-molybdenum disulfide core shells unified with nitrogen-rich amorphous carbon nanotube (1T-MoS2/NCNT). The 1T-MoS2/NCNT core-shells composite is prepared using a hydrothermal method to fabricate a ratiometric low-level detection of a 5-NQ sensor. The screen-printed carbon electrode (SPCE) modified with 1T-MoS2/NCNT reveals superior electrochemical performance for the detection of 5-NQ with a wide dual linear range of 0.03–258.58 µM and 274.91–604.25 µM, low-level detection limit (LOD) of 0.0089 µM, and a higher sensitivity of 1.83 µA µM−1 cm−2 due to its higher electrochemical active surface area, superior conductivity, and excellent stability. The π-delocalized electrons in 5-NQ facilitate the rapid electron transfer at the electrode-electrolyte interface, allowing easy conjugation with 1T-MoS2/NCNT. The operational stability of the sensor retains 98.7 % after 40 consecutive cycles. In addition, the achieved recovery rates are 96.80–99.76 % and 97.93–99.75 % for 5-NQ detection in various soils and water samples, signifying its feasibility for real-time industrial waste monitoring.

Effect of hydrothermal reaction temperature on MoO3 nanostructure properties for enhanced electrochemical performance as an electrode material in supercapacitors

This study aims to enhance electrochemical energy storage in supercapacitors by optimizing the synthesis temperature of MoO3 nanostructures using a hydrothermal technique. MoO3 nanostructures were synthesized using a hydrothermal technique, with reaction temperatures ranging from 140 to 230 °C for 24 h. The materials were analyzed using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. The findings indicate that at 200 °C, a pure hexagonal phase of MoO3 was obtained, while different temperatures resulted in a combination of orthorhombic and hexagonal phases. The SEM analysis demonstrated that the morphology of the MoO3 nanostructures varied depending on the synthesis temperature. These variations encompass the particles, spherical planar structures, and nanorods. The prepared samples were subjected to electrochemical analysis to explore their electrochemical properties, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD). The electrochemical performances of the prepared samples varied depending on the temperature at which the MoO3 samples were prepared, resulting in different morphologies. The sample prepared at 220 °C exhibited the highest specific capacitance (CS) of 330 F/g, a minimal charge-transfer resistance (RCT) of 1800 Ω, an energy density of 16.50 Wh/kg, and a power density of 150 W/kg with symmetric and asymmetric device CS values of 125 and 115 F/g, respectively, compared to the other prepared samples. The observed outcomes can be attributed to the diverse morphology of MoO3 nanostructures and the high electrochemical active surface area (ECSA) of 7.43 × 10−5 F/cm2 that were synthesized at different hydrothermal temperatures. This diversity in morphology and ECSA leads to the presence of active surface area sites, thereby enhancing electrochemical activity. These findings highlight the effect of synthesis temperature on the morphology, crystal structure, and electrochemical performance of MoO3 nanostructures for supercapacitor applications.

Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates.

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, a high-density semi-metallic molybdenum disulfide (1T'-MoS2) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieve high capacitance up to ≈277.5Fcm-3 under an ultrahigh scan rate of 1000mVs-1 with a lower charge-transfer resistance and nearly tenfold higher electrochemical active surface area than the 2H-MoS2 electrode, is reported. Furthermore, 1T'-MoS2 electrode demonstrates exceptional volumetric desalination capacity of 65.1mgNaClcm-3 in CDI experiments. Ex situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS2 interlayer to accommodate cations such as Na+, K+, Ca2+, and Mg2+, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact 2D-layered nanolaminates with high-volumetric performance for CDI desalination.

Controllable boosting activity on Co4N by Fe substitution for oxygen evolution reaction and efficient 5-hydroxymethylfurfural oxidation

The design of transition metal nitrides with excellent oxygen evolution reaction and 5-hydroxymethylfurfural oxidation reaction (HMFOR) is of great significance to achieve the goal of "carbon peaking and carbon neutrality". Herein, Fe-doped bimetallic nitride FexCo1-x)4N was prepared by a simple electron regulation strategy. The introduction of Fe changes the electronic structure of Co and optimizes the adsorption energies of *OH, reduces the potential barrier for the generation of *OOH as a potential-determining step and thus increases the intrinsic OER activity of Co4N. In addition, Fe substitution of some of the Co atoms gives (FexCo1-x)4N a higher electrochemical active surface area, which accelerates the electron transfer efficiency and improves the electrical conductivity. The overpotential for (FexCo1-x)4N-0.9 to reach a current density of 10 mA cm−2 in 1 M KOH is only 271 mV. When in 1 M KOH + 50 mM HMF condition, (FexCo1-x)4N-0.9 requires only 1.37 V to reach a current density of 10 mA cm−2. This work provides practical guidance for developing bifunctional transition metal electrocatalysts with excellent OER and HMFOR activity.

Electrocatalytic sensing of propyl gallate in real-time food samples using a synergistic Sm-MOF@GCN composite modified glassy carbon electrode

A novel electrochemical sensor has been developed using the sonochemically synthesized samarium metal–organic framework (Sm-MOF) and the graphitic carbon nitride (GCN) composite for the selective determination of propyl gallate (PG). The as-synthesized Sm-MOF@GCN composite was characterized by XRD, XPS, and FESEM. The morphological studies of the prepared Sm-MOF@GCN composite revealed the bar-shaped Sm-MOF and porous sheet-like morphology of GCN. The combined effect of the Sm-MOF and GCN enhance the current density response and lowers the oxidation potential, which was beneficial for the electrochemical sensing of PG. Moreover, the high electrochemical active surface area (EASA) (0.0649 cm2) and the rate constant value (Ko) of 1.44x10-5 cm s−1 confirm the faster electron transfer kinetics at the interface of Sm-MOF@GCN composite. However, the developed Sm-MOF@GCN composite possesses linear range from 0.02 to 60 µM with a nanomolar detection level (2.05 nM), high sensitivity (0.1914 μA μM−1 cm−2), excellent reproducibility, repeatability, and stability for up to 30 days towards the PG detection. Finally, the Sm-MOF@GCN composite-modified electrocatalyst was utilized for the quantification of PG in foodstuffs such as instant noodles, cookies, cakes, and oils. The result of the study, the Sm-MOF@GCN composite displayed good recovery results, making it a promising candidate for detecting PG in real-world samples in view of its binder-free approach and facile fabrication process.

Preparation of highly active and durable electrodes for alkaline water electrolysis by anodizing of commercial FeNi and FeNiCo alloys

Anodizing is gaining popularity as a binder-free fabrication route for obtaining catalyst materials directly on the current collector without using noble metals, binders, or conductive carbon additives. Here, we fabricate promising highly active electrodes for alkaline water electrolysis by anodizing commercial FeNi and FeNiCo alloys (%wt. Fe range between 22 and 63) in an ethylene glycol-based fluoride electrolyte. Anodizing forms metal fluoride coatings, which are converted to OER active compounds (γ-NiOOH:Fe) during potential cycling in an alkaline aqueous solution (1 mol L−1 (M) KOH at 293 K) as a result of leaching of fluoride ions. The morphology, thickness, and number of active sites are influenced by the amount of Fe in the alloy, and the electrode with the highest electrochemical active surface area (Kovar alloy with a 54 %wt. Fe) shows the largest OER activity enhancement by anodizing. The performance evaluation in practical conditions (7 mol L−1 KOH at 343 K) demonstrated a highly active performance with an OER potential as low as 1.52 V at a current density of 600 mA cm−2 even for electrodes obtained in alloys with a low amount of Fe (78-Permalloy with a 22 %wt. Fe), demonstrating that anodizing is an effective way to develop highly active OER electrodes from commercially available alloys. On the other hand, anodizing is a good fluoridation route for transition metals with good results in the formation of F-enriched precursors that efficiently promote active phase formation during the catalytic process, offering the possibility of obtaining catalysts directly on the current collector in a one-step process, easily implemented in industrial applications.

Green and sustainable use of macadamia nuts as support material in Pt-based direct methanol fuel cells

The successful commercialization of direct methanol fuel cells (DMFCs) is hindered by inadequate methanol oxidation activity and anode catalyst longevity. Efficient and cost-effective electrode materials are imperative in the widespread use of DMFCs. While Platinum (Pt) remains the primary component of anodic methanol oxidation reaction (MOR) electrocatalysts, its utilization alone in DMFC systems is limited due to carbon monoxide (CO) poisoning, instability, methanol crossover, and high cost. These limitations impede the economic feasibility of Pt as an electrocatalyst. Herein, we present the use of powdered activated carbon (PAC) and granular activated carbon (GAC), both sourced from macadamia nut shells (MNS), a type of biomass. These bio-based carbon materials are integrated into hybrid supports with reduced graphene oxide (rGO), aiming to enhance the performance and reduce the production cost of the Pt electrocatalyst. Electrochemical and physicochemical characterizations of the synthesized catalysts, including Pt-rGO/PAC-1:1, Pt-rGO/PAC-1:2, Pt-rGO/GAC-1:1, and Pt-rGO/GAC-1:2, were conducted. X-ray diffraction analysis revealed crystallite sizes ranging from 1.18 nm to 1.68 nm. High-resolution transmission electron microscopy (HRTEM) images with average particle sizes ranging from 1.91 nm to 2.72 nm demonstrated spherical dispersion of Pt nanoparticles with some agglomeration across all catalysts. The electrochemical active surface area (ECSA) was determined, with Pt-rGO/GAC-1:1 exhibiting the highest ECSA of 73.53 m2 g−1. Despite its high ECSA, Pt-rGO/GAC-1:1 displayed the lowest methanol oxidation reaction (MOR) current density, indicating active sites with poor catalytic efficiency. Pt-rGO/PAC-1:1 and Pt-rGO/PAC-1:2 exhibited the highest MOR current densities of 0.77 mA*cm−2 and 0.74 mA*cm−2, respectively. Moreover, Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 demonstrated superior electrocatalytic mass (specific) activities of 7.55 mA/mg (0.025 mA*cm−2) and 7.25 mA/mg (0.021 mA*cm−2), respectively. Chronoamperometry tests revealed Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 as the most stable catalysts. Additionally, they exhibited the lowest charge transfer resistances and highest MOR current densities after durability tests, highlighting their potential for DMFC applications. The synthesized Pt supported on PACs hybrids demonstrated remarkable catalytic performance, stability, and CO tolerance, highlighting their potential for enhancing DMFC efficiency.

Insights into synergetic modulation of nickel sites over graphene by introducing tungsten and light for efficient methanol electrooxidation

Cut-lost, highly active and stable (photo-)electrocatalysts are earnestly expected to overcome high energy obstacles in methanol oxidation reaction (MOR). A hybrid of NiW/graphene (NiW/G) is prepared by a simple self-designed electrosynthesis method. During the process of electrosynthesis, exfoliation of bulky graphite into graphene and generation of multivalent NiW bimetal precursor are both achieved. This obtained composite displays superior photoelectrocatalytic performance towards MOR. As for NiW/G-light, its area activity (peak current) and mass activity (peak current) are up to 343.4 mA cm−2 and 5960.7 mA mg−1 respectively, much higher than NiW/G, Ni/G and W/G. Operando electrochemical impedance spectroscopy, in-situ Fourier transform infrared spectroscopy and other ex-situ techniques uncover that the excellent MOR performance for NiW/G-light results from synergetic modulation of nickel sites by introducing tungsten and light, which provides desired adsorption behavior and high electrochemical active surface area. It’s found that introduction of W component promotes the formation of W-O-Ni(Ni3+) species, supporting more strong adsorption sites for methanol. This results in new reaction path between adsorbed methanol and OH* for producing formic acid. With application of light, the photo-generated hole promotes oxidation of residual Ni2+ into Ni3+ species, which provides additional formed NiOOH sites for MOR. It’s concluded introduction of tungsten and light is efficient for greatly enhancing methanol electrooxidation. This work is highly instructive for application of self-designed electrosynthesis method to construct dimetal/graphene composite and photoelectric synergistic catalysis towards MOR.

Polyol-assisted synthesis of NdFeO3 nanoparticles decorated porous N-CNTs for voltammetric sensing of furazolidone in veterinary feeds and urine samples

In modern medicine, antibiotics with nitro groups were crucial for the treatment of urinary tract and bacterial infections in humans and animals. However, prolonged or excessive use of it harms the environment, humans, and animals health. Therefore, fast, accurate, and low-cost sensors have become essential for monitoring the use of drug quantities. Electrochemical methods are appropriate for determining drugs in real samples. In this work, NdFeO3 nanoparticles decorated on porous N-CNTs (NFO/N-CNTs) nanocomposite constructed through a polyol-mediated reflux heating method and explored for electrochemical applications. Various spectroscopic and analytical techniques were employed to analyze the formation of the nanocomposite. The as-synthesized NFO/N-CNTs nanocomposite possesses higher electrochemical active surface area, improved conductivity, and enhanced electrochemical activity compared to pure NdFeO3 due to the decoration of N-CNTs. The prepared nanocomposite was applied for electrochemical sensing of FZD in veterinary feeds and urine samples. The fabricated electrode NFO/N-CNTs modified glassy carbon electrode possesses a wide linear range of 0.0025–152.76 µM, a low limit of detection of 0.008 µM and a high sensitivity of 1.695 μA μM−1 cm−2 toward FZD. Furthermore, it shows significant anti-interfering ability, stability, repeatability, and reproducibility during FZD monitoring. The identification of FZD in veterinary feeds and urine samples using an NFO/N-CNTs sensor achieved acceptable results.

Cathodic luminol electrochemiluminescence on TiO2 nanotube array

This study introduces a novel fabrication of screen-printed electrode of hierarchical thin layers of TiO2 nanotube arrays (TNA) and its preliminary investigation for cathodic electrochemiluminescence (ECL) of luminol. The TNA growth on titanium foil by anodization technique was studied under various anodization times and counter electrodes (Pt wire and stainless-steel plate). Characterization using FTIR, UV-VIS DRS, and XRD revealed the increase of TiO2 formation at longer anodization times. The TNA synthesized with a stainless-steel counter electrode (TNA-SS) for 2000 s exhibited better nanotube growth and a higher electrochemical active surface area compared to the one using Pt counter electrode (TNA-Pt). The SEM characterization verified the nanotube morphology of TNA-SS with an average pore diameter of 50.46 nm and a tube length of ∼1100 nm. Notably, when TNA applied as the working electrode for the ECL of luminol, a reduction peak at −0.8 V accompanied by a clear ECL signal were observed, reaching an optimum intensity at 15 μM luminol. A comparative analysis between TNA-SS and TNA-Pt revealed the same trend of ECL signals with a significantly higher ECL intensity of TNA-SS than that of TNA-Pt. The ECL intensity of TNA-SS 2000s was also higher than TNA-SS 300s, confirming the importance of TNA surface area to the ECL activity. Nevertheless, the synthesized SPE-TNA shows great prospect to be applied in electroanalytical and sensing fields, offering opportunities for the development of electrochemiluminescence technologies.

Investigating the electrochemical performance of MnSe-supported SrZrO3 perovskite oxide nanocomposite as an electrode material for supercapacitor

Currently, the advancement in energy storage technology is a worldwide-based vital challenge, so researchers focused on the development and design of promising electrode materials for energy storage equipment. Perovskite oxide and transition metal selenide nanocomposites can achieve better cycle stability, efficient electric conductivity, high capacity, excellent redox reaction, and inattentive flexibility as electrode materials for energy storage devices and supercapacitor applications. Herein, we present the designed, fabricated, and electrochemical properties of MnSe-supported SrZrO3 nanocomposite via the Pechini method that exhibited more efficient capacitive performance than pristine SrZrO3 and MnSe. The result of electrochemical testing indicates that the SrZrO3–MnSe nanocomposite electrode possessed a battery-type pseudocapacitive nature and displayed a boosted specific capacitance of 1204 Fg-1 at a 5 mV/s scan rate in aqueous 1 M KOH solution under a three-electrode setup and maintained 95.2% retention after 3000th cycles. It also showed a higher electrochemical active surface area (1680.5 cm2), higher energy density (40 Wh/Kg), long-term cyclic stability performance, and enhanced rate capability compared to other prepared products. As a result, these findings have shown that SrZrO3–MnSe nanocomposite can be considered as potential electrode materials and might have emerging applications in commercial products for energy storage devices and supercapacitors.

Accelerating photoelectrochemical CO2RR selectively of C2+ products by integrating Ag/Pd cocatalysts on Cu/Cu2O/CuO heterojunction nanorods

The Cu-based photoelectrochemical CO2 reduction reaction (PEC–CO2RR) represents a convenient approach for producing value-added C2+ products, aiming to achieve carbon neutrality by reducing greenhouse gas emissions. However, these reactions typically suffer from limited selectivity. In this work, we fabricate Cu/Cu2O/CuO nanorod (CuR)-based heterojunction architectures integrated with Ag and Pd cocatalysts to boost the selectivity of C2+ products. The proposed Cu/Cu2O/CuO/Ag-Pd (CuR/Ag-Pd) photoelectrodes are used as photocathodes to generate a maximum Faradaic efficiency (FE) of C2+ products exceeding 53% by suppressing the hydrogen evolution reaction (HER). The FE improvement is approximately 22-fold (n-propanol), 12-fold (ethanol), 13-fold (acetaldehyde), and 6-fold (acetate) compared with CuR photoelectrodes operating at a negative applied potential of −1.8 V (vs. reversible hydrogen electrode, RHE). Conversely, the CuR photoelectrodes exhibit a maximum HER rate of ∼86% at −1.8 V (vs. RHE), higher than those of the CuR/Ag (54%) and CuR/Ag-Pd (35%) photoelectrodes. The superior PEC–CO2RR performance of CuR/Ag-Pd photoelectrodes is attributable to the higher electrochemical active surface area (6.7 mF/cm2) and faster charge transfer rate at the electrode/electrolyte interface owing to the presence of cocatalysts. In addition, the CuR/Ag-Pd photoelectrodes exhibit remarkable long-term stability retaining 70% of the initial performance even after a relatively more negative applied potential at −1.2 V. A comprehensive investigation into the changes in surface morphology, crystal structure, and elemental composition after PEC–CO2RR confirms the higher stability of CuR/Ag-Pd photoelectrodes. Thus, this work provides novel perceptions into the development of Cu-based heterojunction photoelectrodes integrated with Ag/Pd cocatalysts for improving the selectivity of C2+ products.

Function‐Oriented Design of Amorphous MoS2 with Abundant Active Sites for High‐Efficiency Hydrogen Evolution Reaction

AbstractMolybdenum disulfide (MoS2) has received great interest as a highly active and cost‐effective electrocatalyst for hydrogen evolution reaction (HER). However, a main challenge for developing high‐efficiency electrocatalysts is to tailor the factors affecting the HER performance, such as composition, structure, and morphology. Herein, amorphous MoS2 electrodes with different Mo and S contents are successfully synthesized by the chemical bath deposition method using different molar ratios of Mo/S precursors (Mo/S: 4 : 1, 1 : 1 and 1 : 4) at various growth times. Experimental results indicate that the composition and the surface morphology of MoS2 are strongly sensitive to the Mo and S contents, which can create different surface roughness at the interface induced by growth times. The as‐prepared MoS2 electrode with a molar ratio of 1 : 4 exhibits superior HER activity in 1 M KOH, only requiring low overpotentials of 220 mV at 20 mA cm−2, which is much lower than those of MoS2 with a molar ratio of 1 : 1 (253 mV), and 4 : 1 (290 mV), respectively. This outstanding electrochemical performance of MoS2 (Mo/S, 1 : 4) with excellent long‐term stability can be attributed to its unique sulfur‐rich MoS2 nanosheet array structure with exposed abundant active sites, a high electrochemical active surface area (ECSA: 955.50 cm2) and superior roughness factor (RF: 3822).

Controlled synthesis of reduced graphene oxide-supported bimetallic Pt–Au nanoparticles for enhanced electrooxidation of methanol

Controlled construction of bimetallic interfaces on conductive carbon supports is extremely important for achieving better synergistic effect required for electrooxidation of small organic molecules for energy applications. Herein, controlled synthesis of reduced graphene oxide (RGO)-supported bimetallic Pt–Au nanoparticles (Pt–Au/RGO) for electrooxidation of methanol using a facile and practical approach was described. By carefully adapting sequential and simultaneous reduction steps H2PtCl6 and AuCl3were reduced on RGO support using ammonia borane (AB) and ascorbic acid (AA) as reducing agents. Three types of Pt–Au/RGO catalysts were prepared and labeled as PtAu/RGO-AB1, PtAu/RGO-AB, and PtAu/RGO-AA. The reduction process was carried at ambient conditions, without the use of surfactants, and the catalysts obtained were analyzed through various techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS). The PtAu/RGO-AB1 catalyst showed remarkable uniformity on the RGO sheets, with an average particle size of 2–3 nm. The electrochemical behavior of Pt–Au catalysts supported on reduced graphene oxide (RGO) for methanol oxidation was systematically investigated via cyclic voltammetry and chronoamperometry techniques. Among the studied catalysts, PtAu/RGO-AB1 exhibited high electrochemical active surface area (ECSA) of 92.47 m2/g, along with the highest mass and ECSA-normalized activities for the electrooxidation of methanol. PtAu/RGO-AB1 manifested exceptional resistance to accumulated CO-like species, as evidenced by its higher forward peak current density to reverse peak current density ratio (If/Ib) of 2.20. The facile and effective synthesis strategy described here provides a promising method for fabricating well-defined multi-component nanostructured electrocatalysts with potential applications for various fuel cell reactions.