Activity For Electrooxidation Research Articles

Boosting urea electro-oxidation activity by pairing nanoporous nickel with borate anions

Boosting urea electro-oxidation activity by pairing nanoporous nickel with borate anions

Rational design of cobalt oxide nanocubes arrays on Ni foam as durable and robust electrocatalyst for urea electro-oxidation

BackgroundCobalt oxide (Co3O4) is a promising electrocatalyst for efficient urea electro-oxidation, tackling power consumption and environmental challenges. The controllable design of free-standing Co3O4 nanostructures grown on Ni foam (NF) substrates was achieved using a green and facile hydrothermal approach. Different reducing agents were applied to synthesize various morphological structures of Co3O4, including nanoparticles, nanowires, and nanocubes (NCs) morphologies.ResultsThe as-fabricated electrodes were investigated as electrocatalysts for enhanced urea electro-oxidation. Because of its 3D nanostructure with minimal agglomeration and a large interfacial surface area with adequate electroactive sites, the Co3O4 NCs/NF had the best energy conversion efficiency of any electrode toward the urea oxidation process. These distinctive features facilitated the electron and urea routes used in the urea electro-oxidation process. It had a low-onset potential of 194.2 mV (vs. Hg/HgO) and a current density of 90.2 mA cm−2 in a 1 M KOH electrolyte. The electrocatalyst demonstrated excellent anodic activity for urea electro-oxidation with an onset potential of 196.7 mV and a current density of 256.1 mA cm−2 in 1 M KOH + 0.3 M urea concentration. Furthermore, the Co3O4 NCs/NF exhibited long-term stability, as shown by chronoamperometry and stepwise tests after 3600 s in the presence of urea under various operating conditions.ConclusionsCompared to all the fabricated Co3O4 nanostructures, the Co3O4 nanocubes revealed the highest electrocatalytic performance toward urea electro-oxidation in all concentrations. Therefore, Co3O4 NCs/NF is a promising, robust, and efficient electrocatalyst for direct urea fuel cell applications.

Evaluation of Active Oxygen Species Derived fromWater Splitting for ElectrocatalyticOrganic Oxidation.

Active oxygen species (OH*/O*) derived from water electrolysis are essential for the electrooxidation of organic compounds into high-value chemicals, which can determine activity and selectivity, whereas the relationship between them remains unclear. Herein, using glycerol (GLY) electrooxidation as a model reaction, we systematically investigated the relationship between GLY oxidation activity and the formation energy of OH* (ΔGOH*). We first identified that OH* on Au demonstrates the highest activity for GLY electrooxidation among various pure metals, based on experiments and density functional theory, and revealed that ΔGOH* on Au-based alloys is influenced by the metallic composition of OH* coordination sites. Moreover, we observed a linear correlation between the adsorption energy of GLY (Eads) and the d-band center of Au-based alloys. Comprehensive microkinetic analysis further reveals a volcano relationship between GLY oxidation activity, the ΔGOH* and the adsorption free energy of GLY (ΔGads). Notably, Au3Pd and Au3Ag alloys, positioned near the peak of the volcano plot, show excellent activity, attributed to their moderate ΔGOH* and ΔGads, striking a balance that is neither too high nor too low. This research provides theoretical insights into modulating active oxygen species from water electrolysis to enhance organic electrooxidation reactions.

Exploring the performance of ammonia microfluidic fuel cell using PdNiCo aerogel

In this manuscript, PdNiCo and NiCo aerogel catalysts are prepared by an ultrafast sol-gel method combining microwave heating and freeze-drying. These new aerogels are synthesized to explore the transition metal content compared to a Pd aerogel in order to minimize the dependence on noble metals and improve their electrocatalytic properties in the presence of ammonia. The textural properties of the aerogels were characterized by the N2 adsorption/desorption isotherms. The crystal structures were measured by X-ray diffraction and X-ray photoelectron spectroscopy was used to analyze the electronic structures of the elements. The electrocatalytic activity of the aerogels towards the ammonia oxidation reaction was tested by cyclic voltammetry in a 1 M KOH + 1 M NH4OH solution. The combination of these properties in the PdNiCo and NiCo aerogels enhances the electrocatalytic activity of ammonium electro-oxidation compared to that of the Pd aerogel alone, and the multimetallic aerogels are more stable when used in a microfluidic device such as an ammonia fuel cell.

Evaluation of Active Oxygen Species Derived from Water Splitting for Electrocatalytic Organic Oxidation

AbstractActive oxygen species (OH*/O*) derived from water electrolysis are essential for the electrooxidation of organic compounds into high‐value chemicals, which can determine activity and selectivity, whereas the relationship between them remains unclear. Herein, using glycerol (GLY) electrooxidation as a model reaction, we systematically investigated the relationship between GLY oxidation activity and the formation energy of OH* (ΔGOH*). We first identified that OH* on Au demonstrates the highest activity for GLY electrooxidation among various pure metals, based on experiments and density functional theory, and revealed that ΔGOH* on Au‐based alloys is influenced by the metallic composition of OH* coordination sites. Moreover, we observed a linear correlation between the adsorption energy of GLY (Eads) and the d‐band center of Au‐based alloys. Comprehensive microkinetic analysis further reveals a volcano relationship between GLY oxidation activity, the ΔGOH* and the adsorption free energy of GLY (ΔGads). Notably, Au3Pd and Au3Ag alloys, positioned near the peak of the volcano plot, show excellent activity, attributed to their moderate ΔGOH* and ΔGads, striking a balance that is neither too high nor too low. This research provides theoretical insights into modulating active oxygen species from water electrolysis to enhance organic electrooxidation reactions.

Efficient stabilizing agent-free synthesis of gold nanoparticles via square-wave pulse deposition for enhanced catalytic performance in ethanol electrooxidation

The pressing environmental concerns and the depletion of fossil fuel reserves necessitate a transition toward sustainable energy sources. Ethanol, a renewable biomass-derived fuel, is a promising alternative due to its availability and high energy density. This study investigates the synthesis of gold nanoparticles (AuNPs) via a square-wave pulse deposition technique, aiming to enhance catalytic activity for ethanol electrooxidation. By varying pulse durations, we were able to exert precise control over AuNP size and distribution without stabilizing agents. Characterization using field emission scanning electron microscopy and X-ray diffraction techniques confirmed the formation of clustered nanoparticles of metallic gold phase. Electrochemical characteristics analyses revealed that AuNPs synthesized with a 900 ms pulse duration exhibited the lowest charge transfer resistance and the highest electrochemically active surface area. The electrocatalytic performance test of these AuNPs demonstrated an anodic current density of 2.5 mA cm-2 and a Tafel slope of 78 mV dec-1, indicating superior catalytic performance and reaction kinetics. Additionally, the AuNPs showed high resistance to poisoning, as evidenced by a low jb/jf ratio of 0.28 and stable chronoamperometric response. These findings underscore the potential of this synthesis method for producing high-performance electrocatalysts utilized in exploiting ethanol's potential as an environmentally friendly energy carrier.

Bioflocculant polymer reduced CuO/NiO binary transition metal oxide nanocomposite: Application as an effective non-enzymatic glucose sensor

A bimetallic copper oxide/nickel oxide nanocomposite (CuO/NiO NCs) was synthesized via direct carbonization method by using microbial polymer as reducing agent. This nanocomposite was employed as a viable non-enzymatic electrocatalyst in the glucose detection. It was completely characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopic (EDX) methods and revealed the obtained porous nanoflower morphology with particle sizes of 100–200 nm in a monoclinic face-centered cubic crystalline structure. FT-IR spectra confirmed the presence of functional groups and the purity of the nanocomposite. Electrocatalytic performance for glucose oxidation was evaluated through cyclic voltammetric (CV) and amperometric i-t techniques. The observation demonstrated that the CuO/NiO NCs exhibited a remarkable electro-oxidation activity against glucose, attributed to the synergistic effects of the bimetallic components. As an electrode surface modifier, the CuO/NiO NCs facilitated an enhanced glucose oxidation over a linear range of 1–9 mM via CV, while amperometric i-t measurements achieved a detection range from 0.04 μM to 4.86 mM in a 0.1 M NaOH (pH ∼ 13) electrolyte solution. These eco-friendly and in-expensive nanoflowers displayed excellent selectivity, stability, and reproducibility, underscoring their potential in diabetes monitoring and the subsequent scientific analysis.

Enhanced performance of CNT supported bimetallic PdM (M=Cr, Ta, Bi, Hf) catalysts as anode electrode for ammonia borane electrooxidation

Herein, carbon nanotube (CNT) supported PdM (M=Cr, Ta, Bi, Hf) catalysts are prepared by sodium borohydride (NaBH4) reduction method. The analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and X-ray photoelectron spectroscopy (XPS) are utilized for the characterization of the bimetallic catalysts. The ammonia borane electrooxidation activities of the bimetallic catalysts are defined by cyclic voltammetry (CV) measurements. The stability of the bimetallic catalysts and resistance to ammonia borane electrooxidation are determined by using chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements. The highest catalytic activity for ammonia borane electrooxidation is obtained as 52.60 mA/cm2 with PdCr/CNT catalyst. PdCr/CNT catalyst with high catalytic activity could be promising as an anode catalyst for direct ammonia borane fuel cell.

Enhanced Hydrazine Electrooxidation Activities on Novel Benzofused Tricyclic Heterocyclic Derivatives.

In this study, some benzofused tricyclic heterocyclic derivatives have been tested as possible new catalysts for anode hydrazine electrooxidation in a direct hydrazine fuel cell (DHFC). Electrochemical studies were carried out in solution media containing 1 M KOH and 1 M KOH + 0.5 M N2H4 using electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). The CV results obtained showed that 5 catalysts promoted the generation of the best current (38.32 mA/cm2), and EIS results confirmed that an electrode modified with the same derivative presented the lowest charge transfer resistance. All these results proved that 5 organic-based catalysts can be used as an anode-efficient catalyst in hydrazine fuel cells.

Facile and innovation synthesis of Zn-Mn-Co-LDH/polypyrrole and its application in investigating ethanol oxidation in an alkaline medium

Overvoltage and low current are observed for ethanol electrooxidation on the surface of many unmodified electrodes. Therefore, it is desirable to use a suitable catalyst for ethanol electrooxidation to increase the current. This research introduces a new sensor to catalyze ethanol oxidation in an alkaline environment. This new Zn-Mn-Co LDH/PolyPyrrole/GCE nanocomposite sensor exhibits high catalytic activity for ethanol electrooxidation. It changes the oxidation potential of ethanol to a less positive potential. To identify this proposed sensor, X-ray diffraction (XRD), Brauner Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy, field emission scanning electron microscopy (FESEM), thermal analysis (TGA), high-resolution transmission electron microscopy (HR-TEM) and cyclic voltammetry techniques were used. Ethanol electrooxidation was investigated by cyclic voltammetry technique. The effects of scan rate and ethanol concentration on the ethanol oxidation peak have been investigated. The proposed sensor showed long-term stability. This prepared nanocomposite can be used as an anode catalyst for ethanol fuel cells.

An efficient voltammetric sensing platform for trace determination of Norfloxacin based on nanoplate-like α-zirconium phosphate/carboxylated multiwalled carbon nanotube nanocomposites

Norfloxacin (NOR) residues pose a potential threat to our health and ecosystem, so it is highly urgent to develop a simple but accurate method for NOR determination. Therefore, an efficient voltammetric sensing platform was constructed for trace detection of NOR based on nanoplate-like α-zirconium phosphate/carboxylated multiwalled carbon nanotubes (α-ZrP/CMWCNT). The physiochemical characteristics of α-ZrP/CMWCNT were scrutinized using various microscopic, spectroscopic, and electrochemical means. In order to pursuit higher voltammetric responses, detection conditions of NOR such as accumulation potential, accumulation time and buffer pH, were explored comprehensibly. The α-ZrP/CMWCNT enlarged the electrochemically active surface area and lowered the charge transfer resistance. Owing to the synergistic interactions between nanoplate-like α-ZrP NPs and CMWCNTs, the α-ZrP/CMWCNT boosted the voltammetric response signals and reduced the over-potential of NOR. Consequently, the α-ZrP/CMWCNT demonstrated remarkably catalytic activity for NOR electrooxidation, with two broad linear detection ranges (0.01–0.1 μM; 0.1–10.0 μM) and a low detection limit (2.8 nM). The α-ZrP/CMWCNT modified glassy carbon electrode (GCE) exhibited strong anti-interfering ability even in excess of other antibiotics and common metal ions, and maintained robust response peaks up to two weeks. The α-ZrP/CMWCNT/GCE realized accurate determination of NOR from complicated matrices at trace levels with good recoveries (99.00–104.40 %).

Ultrasonic-assisted Fenton reaction inducing surface reconstruction endows nickel/iron-layered double hydroxide with efficient water and organics electrooxidation

Nickel/iron-layered double hydroxide (NiFe-LDH) tends to undergo an electrochemically induced surface reconstruction during the water oxidation in alkaline, which will consume excess electric energy to overcome the reconstruction thermodynamic barrier. In the present work, a novel ultrasonic wave-assisted Fenton reaction strategy is employed to synthesize the surface reconstructed NiFe-LDH nanosheets cultivated directly on Ni foam (NiFe-LDH/NF-W). Morphological and structural characterizations reveal that the low-spin states of Ni2+ (t2g6eg2) and Fe2+ (t2g4eg2) on the NiFe-LDH surface partially transform into high-spin states of Ni3+ (t2g6eg1) and Fe3+ (t2g3eg2) and formation of the highly active species of NiFeOOH. A lower surface reconstruction thermodynamic barrier advantages the electrochemical process and enables the NiFe-LDH/NF-W electrode to exhibit superior electrocatalytic water oxidation activity, which delivers 10 mA cm−2 merely needing an overpotential of 235 mV. Besides, surface reconstruction endows NiFe-LDH/NF-W with outstanding electrooxidation activities for organic molecules of methanol, ethanol, glycerol, ethylene glycol, glucose, and urea. Ultrasonic-assisted Fenton reaction inducing surface reconstruction strategy will further advance the utilization of NiFe-LDH catalyst in water and organics electrooxidation.

Inhibiting the Deep Reconstruction of Ni‐Based Interface by Coordination of Chalcogen Anions for Efficient and Stable Glycerol Electrooxidation

AbstractRecently, Ni‐based chalcogenides havedemonstrated remarkable activity and selectivity for alcohol electrooxidation, but the mechanisms remain debated. This study synthesizes Ni‐based electrodeswith different chalcogen anion coordination on nickel nanorod arrays (NiOx/Ni,NiSx/Ni, and NiSex/Ni NRAs). NiSex/Ni NRAsshowcases superior performance (Faradaic efficiency 92.9%) in glycerolelectrooxidation reaction (GOR). In situ spectroscopy reveals that NiSecoordination inhibits deep oxidative reconstruction of the Ni‐based interface, preventingNiOOH phase formation during GOR, enhancing activity and stability of NiSex/NiNRAs. Conversely, NiS and NiO coordination lead to deep reconstruction with NiOOHphase formation, limiting GOR performance. Differently, during competingreaction of GOR, the oxygen evolution reaction (OER) leads to deepreconstruction of NiSex interface due to the instability of Ni‐Sebonds, inducing performance degradation and dissolution of Se components. Furthermechanism investigation elucidates that the rate‐determining step (RDS) ofGOR at the NiSex interface involves oxidation of *C2H3O3 intermediatesthrough H2O adsorption, favoring stable formate production.Contrarily, the RDS at the NiSx, NiOx, and NiOOHinterfaces predominantly focus on the decarboxylation of multi‐carbon intermediates, raisingenergy barriers and over‐oxidizing formate to CO2. These results providenew insights for designing Ni‐based non‐oxide catalysts forefficient and stable electrocatalytic oxidation.

Graphitic Carbon Nitride as a Promising Visible-Light-Activated Support Boosting Platinum Nanoparticle Activity in Ethanol Electrooxidation.

In the present work, exfoliated graphitic carbon nitride (g-CN) is immobilized on carbon paper substrates by a simple electrophoretic route, and subsequently decorated with ultra-low amounts (≈μg/cm2) of Pt nanoparticles (NPs) by cold plasma sputtering. Optimization of preparative conditions allowed a fine tuning of Pt NPs size, loading and distribution and thus a controlled tailoring of g-CN/Pt interfacial interactions. Modulation of such features yielded g-CN-Pt-based anode materials with appealing activity and stability towards the ethanol oxidation reaction (EOR) in alkaline aqueous solutions, as revealed by electrochemical tests both in the dark and under irradiation. The present results provide new insights on the design of nano-engineered heterocomposites featuring improved performances thanks to Pt coupling with g-CN, a low-cost and environmentally friendly visible light-active semiconductor. Overall, this work might open attractive avenues for the generation of green hydrogen via aqueous ethanol electrolysis and the photo-promoted alcohol electrooxidation in fuel cells.

Tuning Crystal Phase of Palladium-Selenium Nanowires for Enhanced Ethylene Glycol Electrocatalytic Oxidation.

Alcohol electrooxidation is pivotal for a sustainable energy economy. However, designing efficient electrocatalysts for this process is still a formidable challenge. Herein, palladium-selenium nanowires featuring distinct crystal phases: monoclinic Pd7Se2 and tetragonal Pd4.5Se for ethylene glycol electrooxidation reaction (EGOR) are synthesized. Notably, the supported monoclinic Pd7Se2 nanowires (m-Pd7Se2 NWs/C) exhibit superior EGOR activity, achieving a mass activity (MA) and specific activity (SA) of 10.4 A mgPd -1 (18.7mA cm-2), which are 8.0 (6.7) and 10.4 (8.2) times versus the tetragonal Pd4.5Se and commercial Pd/C and surpass those reported in the literature. Furthermore, m-Pd7Se2 NWs/C displays robust catalytic activity for other alcohol electrooxidation. Comprehensive characterization and density functional theory (DFT) calculations reveal that the enhanced electrocatalytic performance is attributed to the increased formation of Pd0 on the high-index facets of the m-Pd7Se2 NWs, which lowers the energy barriers for the C─C bond dissociation in CHOHCHOH* and the CO* oxidation to CO2*. This study provides palladium-based alloy electrocatalysts exhibiting the highest mass activity reported to date for the electrooxidation of ethylene glycol, achieved through the crystalline phase engineering strategy.

Explosive Leidenfrost-Droplet-Mediated Synthesis of Monodispersed High-Entropy-Alloy Nanoparticles for Electrocatalysis.

High-entropy-alloy nanoparticles (HEA NPs) exhibit promising potential in various catalytic applications, yet a robust synthesis strategy has been elusive. Here, we introduce a straightforward and universal method, involving the microexplosion of Leidenfrost droplets housing carbon black and metal salt precursors, to fabricate PtRhPdIrRu HEA NPs with a size of ∼2.3 nm. The accumulated pressure within the Leidenfrost droplet triggers an intense explosion within milliseconds, propelling the carbon support and metal salt rapidly into the hot solvent through explosive force. The exceptionally quick temperature rise ensures the coreduction of metal salts, and the dilute local concentration of metal ions limits the final size of the HEA NPs. Additionally, the explosion process can be fine-tuned by selecting different solvents, enabling the harvesting of diverse HEA NPs with superior electrocatalytic activity for alcohol electrooxidation and hydrogen electrocatalysis compared to commercial Pt (Pd) unitary catalysts.

Boosting the Electrolysis of Monosaccharide-Based Streams in an Anion-Exchange Membrane Cell.

A systematic study on the electrochemical reforming of monosaccharides (fructose, glucose, and xylose) using Pt-based anodic electrocatalysts is here presented for the first time to completely optimize the anodic catalyst and electrolyzer operating conditions. First, the electro-oxidation of each molecule was studied using a monometallic (Pt) and two bimetallic (PtNi and PtCo) anodic electrocatalysts supported on graphene nanoplatelets (GNPs). Tests in a three-electrode cell showed superior electrochemical activity and durability of PtNi/GNPs, especially at potentials higher than 1.2 V vs RHE, with the highest electrocatalytic activity in d-xylose electro-oxidation. Then, monometallic (Pt and Ni) and bimetallic electrocatalysts with different Pt:Ni mass ratios (1:1 and 2:1) were studied for d-xylose electro-oxidation, with the 2:1 mass ratio presenting the best results. This electrocatalyst was selected as the most suitable for scale-up to an anion-exchange membrane electrolyzer, where the optimal operating potential was determined. Additionally, stable operating conditions of the electrolyzer were achieved by cyclic H2 production and cathodic regeneration polarization steps. This led to suitable and reproducible H2 production rates throughout the production cycles for renewable hydrogen production from biomass-derived streams.

Constructing 3D sandwich-like structured Ti foam/TiO2−x/SnO2-Sb composite electrodes for the degradation of PPCPs

The fabrication of Sb-doped SnO2 electrode with high catalytic activity and excellent durability for decomposition PPCPs (Pharmaceuticals and personal care products, PPCPs) is challenging. Herein, a Ti3+/Ovs-related TiO2−x is prepared by short-time annealing at low temperature in mixed gas with Zr as a cocatalyst. DFT calculations indicate that the introduction of Ti3+/Ovs defects could promote the formation of more ·OH. Then, the nanoflower rod-like SnO2-Sb catalytic layer supported on dual-defects TiO2−x is successfully synthesized by one-step pulse electrodeposition (PLED) combined with hydrothermal methods (H). This newly pulse electrodeposition technique solves the short lifetime problem of SnO2-Sb nanoflower electrodes current hydrothermal-based methods. 1O2 and ·OH are found to be the primary reactive oxygen species (ROSs) by radical quenching tests and electron paramagnetic resonance analysis. The optimized Ti foam/TiO2−x /SnO2-Sb electrode could degrade over 96.3 % of 20 mg L−1 amoxicillin (AMX) within 30 min, corresponding kinetic constant 0.10228 min−1. This will provide inspiration for the construction of defect engineering and new insights for the development of low-cost and high electrooxidation activity Sb-doped SnO2 electrode.

Constructing heterostructure of Mo-doped Co(CO3)0.5OH on NiCo2S4 nanowires towards electrocatalytic biomass upgrading

The development of an advanced electrocatalyst is crucial to achieve low-cost and efficient biomass electrooxidation for assisting its practical application. In this study, we design a unique heterostructure of Mo-doped Co(CO3)0.5OH coating on NiCo2S4 nanowires for efficient xylose oxidation reaction (XOR). The as-prepared electrocatalyst requires only 1.28 V for XOR to achieve current density of 50 mA cm−2, and the electrocatalytic system exhibits the high formic acid (FA) yield of 63.22 % and excellent selectivity of 96.52 %, which still maintains unchanged after seven cycles. Furthermore, the two-electrode system by coupling XOR and hydrogen evolution reaction (HER) shows that product selectivity remained at least 96 %, while the hydrogen production rate higher than the original. This remarkable performance is attributed to the synergic effect of heterostructure and multi-component as confirmed by XPS and XRD analysis. This work puts forward an attractive approach for designing high electrocatalytic activity and selectivity electrocatalyst for biomass electrooxidation.

Research on preparation of high activity and durable carbon-supported platinum catalyst for methanol electro-oxidation by a facile continuous microwave pipeline method

In methanol oxidation reaction (MOR), it is crucial for the catalyst that Pt particles uniformly cover the surface of the carrier and the Pt surface active sites can effectively remove the binding with CO. This article develops a simple and effective continuous microwave technology. Carbon loaded nano platinum was synthesized by rapidly and uniformly heating a ethylene glycol mixture containing carbon black (CB) H2PtCl6 using microwave radiation, with a Pt content of 49.5%. The experimental results indicate that platinum particles are uniformly loaded onto the carbon surface, with uniform shape and size, and an average particle size of 3.02 nm. And the Pt/C catalyst prepared by continuous microwave technology showed enhanced electrocatalytic activity (peak current density of 76.95 mA/cm2) in MOR after heating at appropriate temperature in N2 atmosphere, which exceeded the commercial catalyst TKK (47.07 mA/cm2) by 63.6%. And the catalyst's resistance to CO toxicity and durability; Higher than commercial Pt/C catalysts. Compared with traditional methods, continuous microwave technology exhibits higher energy utilization efficiency and faster reaction speed in the catalyst preparation process. This technology also has the ability to achieve continuous preparation, which is one of the effective technological approaches to achieve large-scale catalysts production.