Peroxide Reduction Reaction Research Articles

Watching a Single Enzyme at Work Using Single-Molecule Surface-Enhanced Raman Scattering and DNA Origami-Based Plasmonic Antennas.

The detection of a single-enzyme catalytic reaction by surfaced-enhanced Raman scattering (SERS) is presented by utilizing DNA origami-based plasmonic antennas. A single horseradish peroxidase (HRP) was accommodated on a DNA origami nanofork plasmonic antenna (DONA) containing gold nanoparticles, enabling the tracing of single-molecule SERS signals during the peroxide reduction reaction. This allows monitoring of the structure of a single enzymatic catalytic center and products under suitable liquid conditions. Herein, we demonstrate the chemical changes of HRP and the appearance of tetramethylbenzidine (TMB), which works as a hydrogen donor before and after the catalytic reaction. The results show that the iron in HRP adopts Fe4+ and low spin states with the introduction of H2O2, indicating compound-I formation. Density functional theory (DFT) calculations were performed for later catalytic steps to rationalize the experimental Raman/SERS spectra. The presented data provide several possibilities for tracking single biomolecules in situ during a chemical reaction and further developing plasmon-enhanced biocatalysis.

Synergistic enhancement of oxygen vacancy enrichment and morphology regulation in CeO2-NiCo2O4 heterostructure catalysts for high-performance cathodes in direct borohydride-hydrogen peroxide fuel cells

Hydrogen peroxide (H2O2) emerges as a viable oxidant for fuel cells, necessitating the development of an efficient and cost-effective electrocatalyst for the hydrogen peroxide reduction reaction (HPRR). In this study, we synthesized a self-supporting, highly active HPRR electrocatalyst comprising two morphologically distinct components: CeO2-NiCo2O4 nanowires and CeO2-NiCo2O4 metal organic framework derivatives, via a two-step hydrothermal process followed by air calcination. X-ray diffraction and transmission electron microscopy analysis confirmed the presence of CeO2 and NiCo2O4, revealing the amalgamated interface between them. CeO2 exhibits multifunctionality in regulating the surface electronic configuration of NiCo2O4, fostering synergistic connections, and introducing oxygen deficiencies to enhance the catalytic efficacy in HPRR. Electrochemical measurements demonstrate a reduction current density of 789.9 mA·cm−2 at −0.8 V vs. Ag/AgCl. The assembly of direct borohydride-hydrogen peroxide fuel cell (DBHPFC) exhibits a peak power density of 45.2 mW·cm−2, demonstrating durable stability over a continuous operation period of 120 h. This investigation providing evidence that the fabrication of heterostructured catalysts based on CeO2 for HPRR is a viable approach for the development of high-efficiency electrocatalysts in fuel cell technology.

Co‑MOF-Derived Flake-Like Co3O4 Supported Pd Nanoparticles as High-Performance Hydrogen Peroxide Electroreduction Catalysts

Development of highly efficient catalysts for the hydrogen peroxide reduction reaction (HPRR) has been a focus of research for fuel cells using hydrogen peroxide (H2O2) as an alternative cathode oxidant. The carbon-doped flake-like cobalt oxide electrode (Co3O4@C NF) was prepared on nickel foam (NF) by annealing the metal organic framework (MOF). A Co3O4@C/Pd NF (CPNF) electrode was derived from Co3O4@C NF by supporting Pd nanoparticles. Half-cell tests demonstrated that the CPNF electrode exhibited outstanding catalytic performance. The CPNF electrode displayed a high current density of 932 mA cm−2 at −0.8 V (vs Ag/AgCl). This aligns with its low activation energy (7392.8 J mol−1). The electron transfer numbers for the Co3O4@C NF and CPNF electrodes were 2.97 and 3.32, respectively. Incorporating CPNF as the cathode of Direct borohydride-hydrogen peroxide fuel cell (DBHPFC) yielded notable catalytic performance, with a peak power density of 68 mW cm−2. The CPNF electrode exhibited remarkable stability, sustaining continuous current discharge for over 20 h. These electrochemical properties result from the structural characteristics obtained through MOF annealing, which increases the number of exposed active sites and enhances ion transport. Therefore, CPNF stands as a promising cathode catalyst for DBHPFC.

A HPRR-based diatomic catalyst electrochemical biosensor for detecting cancer-related extracellular vesicles.

Cancer-associated extracellular vesicles (EVs) are crucial biomarkers for cancer diagnosis as they contain abundant tumor cell information. To efficiently and accurately detect cancer-associated EVs, an electrochemical hydrogen peroxide reduction reaction (HPRR)-based biosensor was developed, utilizing enzyme-linked immunosorbent and diatomic catalyst strategies for catalytic HPRR current amplification for specific identification and highly sensitive detection. The anti-CXCR4 antibody was immobilized on a Au-plated electrode to selectively capture EVs from the sample. Subsequently, Fe/Cu diatomic catalysts, modified with an anti-CD63 antibody, were bound to the CD63 on the EVs. Quantitative detection of EVs was achieved by measuring the electrical signals from the HPRR catalyzed by the labeled Fe/Cu diatomic catalysts. Under optimized conditions, the electrochemical signals exhibited a linear relationship with EV concentration in the range of 500 to 1 × 107 particles mL-1, with a detection limit of 117 particles mL-1, maintaining accuracy even in FBS. With its affordability, high sensitivity, and ease of use, this sensor holds significant potential for medication guidance and postoperative evaluation.

Electrocatalytic investigation of H2O2 reduction and sensing performance using sulfide modified Au/Pt electrode in alkaline medium

Hydrogen peroxide (HP) is extensively utilized in numerous industries for synthesizing various chemicals and as a fueling vector in direct peroxide fuel cells in place of oxygen molecules. Therefore, it is crucial to detect HP quickly and develop a cost-effective method for this purpose. The Au/Pt electrode surface exhibits no substantial electrocatalytic activity towards HP reduction reaction, although facilitates oxygen reduction reaction (ORR). To address this issue, in this work, S2- ions have been partially immobilized on Au/Pt surface (termed as [sub-S-Au/Pt]). This modified electrode eliminated catalytic sites for oxygen reduction and generated catalytic sites for facilitating the HP reduction reaction. Comprehensive electrochemical investigations and characterizations of the developed sensor were carried out using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), open circuit potential (OCP), chronoamperometry, and Differential pulse voltammetry (DPV) techniques. The relationship between the current response and HP concentration exhibited a wide linear dynamic range (LDR) ranging from 2 to 1500 μM, with a limit of detection (LOD) of 2.3 μM. The sensitivity of the sensor was determined to be 423.7 μA mM−1cm−2. Additionally, this article provides insight into the kinetics of the HP reduction reaction using the [sub S-Au/Pt] electrode in an alkaline medium. The modified electrode surface was characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

Scaling Relation between the Reduction Potential of Copper Catalysts and the Turnover Frequency for the Oxygen and Hydrogen Peroxide Reduction Reactions.

Changes in the electronic structure of copper complexes can have a remarkable impact on the catalytic rates, selectivity, and overpotential of electrocatalytic reactions. We have investigated the effect of the half-wave potential (E1/2) of the CuII/CuI redox couples of four copper complexes with different pyridylalkylamine ligands. A linear relationship was found between E1/2 of the catalysts and the logarithm of the maximum rate constant of the reduction of O2 and H2O2. Computed binding constants of the binding of O2 to CuI, which is the rate-determining step of the oxygen reduction reaction, also correlate with E1/2. Higher catalytic rates were found for catalysts with more negative E1/2 values, while catalytic reactions with lower overpotentials were found for complexes with more positive E1/2 values. The reduction of O2 is more strongly affected by the E1/2 than the H2O2 rates, resulting in that the faster catalysts are prone to accumulate peroxide, while the catalysts operating with a low overpotential are set up to accommodate the 4-electron reduction to water. This work shows that the E1/2 is an important descriptor in copper-mediated O2 reduction and that producing hydrogen peroxide selectively close to its equilibrium potential at 0.68 V vs reversible hydrogen electrode (RHE) may not be easy.

Enhancing electrocatalytic performance and Stability: A novel Prussian Blue-Graphene quantum dot nanoarchitecture for H2O2 reduction

The reduction reaction of hydrogen peroxide (H2O2) stands as a pivotal electrochemical process holding the promise of revolutionizing energy conversion and water treatment applications. Realizing this potential hinges on the development of electrocatalysts that not only exhibit exceptional activity but also demonstrate unwavering stability. Herein, we propose a pioneering electrocatalyst composed of Prussian blue (PB)-graphene quantum dot (GQD) (PB-GQD) nanoarchitecture fabricated through an in-situ electrochemical method. The PB-GQD nanoarchitecture boasts precisely crafted PB nanoparticles (NPs) that exhibit remarkable electrochemical catalytic activity and stability, offering a substantial advancement over conventional PB NPs structure used as a control. The augmentation of electrocatalytic performance in the PB-GQD nanoarchitecture can be attributed to the symbiotic relationship between PB NPs and GQD. This synergy is engendered through electrostatic attraction and/or coordination interactions between PB precursor’s iron cations and GQD’s multivalent polyanions. This unique arrangement accelerates heterogeneous electron transport, endows the structure with abundant electrochemically active sites, and shortens mass transfer lengths. Notably, GQD’s presence, rich with hydroxyl (–OH) and carboxylic (–COOH) groups, mitigates the decomposition of PB NPs into Fe(OH)3 in neutral or higher pH solutions. This preservation mechanism ensures sustained, elevated electrocatalytic performance for H2O2 reduction.

Multifunctional Chiral Chemically-Powered Micropropellers for Cargo Transport and Manipulation.

Practical applications of synthetic self-propelled nano and microparticles for microrobotics, targeted drug delivery, and manipulation at the nanoscale are rapidly expanding. However, fabrication limitations often hinder progress, resulting in relatively simple shapes and limited functionality. Here, taking advantage of 3D nanoscale printing, chiral micropropellers powered by the hydrogen peroxide reduction reaction are fabricated. Due to their chirality, the propellers exhibit multifunctional behavior controlled by an applied magnetic field: spinning in place (loitering), directed migration in the prescribed direction, capture, and transport of polymer cargo particles. Design parameters of the propellers are optimized by computation modeling based on mesoscale molecular dynamics. It is predicted by computer simulations, and confirmed experimentally, that clockwise rotating propellers attract each other and counterclockwise repel. These results shed light on how chirality and shape optimization enhance the functionality of synthetic autonomous micromachines.

Carbon Nanotube-Supported Bimetallic Core-Shell (M@Pd/CNT (M: Zn, Mn, Ag, Co, V, Ni)) Cathode Catalysts for H2O2 Fuel Cells.

M@Pd/CNT (M: Zn, Mn, Ag, Co, V, Ni) core-shell and Pd/CNT nanoparticles were prepared by sodium borohydride reduction and explored as cathode catalysts for the hydrogen peroxide reduction reaction. Electrochemical and physical characterization techniques are applied to explore the characteristics of the produced electrocatalysts. The cyclic voltammetry (CV) experiments show that Zn@Pd/CNT-modified electrodes have a current density of 273.2 mA cm-2, which is 3.95 times higher than that of Pd/CNT. According to the chronoamperometric curves, Zn@Pd/CNT has the highest steady-state current density for the H2O2 electro-reduction process among the synthesized electrocatalysts. Moreover, electrochemical impedance spectroscopy (EIS) spectra confirmed the previous electrochemical results due to the lowest charge transfer resistance (35 Ω) with respect to other electrocatalysts.

Reactant Transport Engineering Approach at Cathode to High Power Direct Methanol Hydrogen Peroxide Fuel Cell

The development of high-power fuel cells could advance the electrification of the transportation sector, including marine and air transport. Liquid-fueled fuel cells are particularly attractive for such applications as they obviate the issue of fuel transportation and storage. Herein, we report a direct methanol hydrogen peroxide fuel cell (DMHPFC) for high-power propulsion applications that delivers 0.8 W cm2 peak power density by using a pH gradient-enabled microscale bipolar interface (PMBI) to effectively meet the incongruent pH requirements for methanol oxidation/peroxide reduction reactions.DMHPFCs are an important alternative to hydrogen-fed polymer electrode membrane fuel cell (PEMFCs) and anion exchange membrane fuel cells (AEMFCs) due to methanol’s high energy density compared to that of hydrogen and superior kinetics of hydrogen peroxide reduction reaction as compared to Oxygen. A unit volume of Hydrogen gas stored at a pressure of approximately 69 MPa corresponds to volume-specific energy density of roughly 2.1 kWh/l while 39% volume of aqueous methanol and 41% volume of aqueous hydrogen peroxide corresponds to volume-specific energy density of 9.2 kWh/l. So, DMHPFC’s energy density is approximately four times higher than hydrogen fuel cell’s energy density and is comparable to gasoline which contains roughly 9.2 kWh/l of available bond energy. The theoretical potential for Methanol oxidation reaction (MOR) in basic medium is lower than that in an acidic medium (-0.78 V vs. -0.02 V) and the theoretical potential for the Hydrogen peroxide reduction reaction (HPRR) is higher than that for oxygen reduction (1.77 V vs. 1.23 V in acidic medium). This results in the highest theoretically possible cell voltage for cells with alkaline anodes and acidic cathodes. We achieved sustained operation of the DMHPFC with an alkaline anode and an acidic cathode by incorporating our pH-gradient-enabled microscale bipolar interface (PMBI).However, the system exhibits a relatively low Faradaic efficiency of 50% due to the parasitic evolution of O2 by the decomposition of H2O2. The O2 evolution results in a mixed potential at the cathode due to the occurrence of both the HPRR (E0 = 1.77 V versus standard hydrogen electrode [SHE]) and the oxygen reduction reaction (ORR); (E0 = 1.23 V versus SHE), lowering the overall cell potential. The O2 surface coverage reduces the available sites for the HPRR, effectively deactivating the catalyst. Electrocatalysts exhibiting a combination of high HPRR activity and selectivity (by inhibiting H2O2 decomposition, and hence inhibiting ORR) would result in higher faradic efficiency and have been the subject of sustained interest. Here, we examine an alternate reactant-transport engineering approach to improve the overall cell potential and cell performance of the DMHPFC. Our reactant-transport engineering approach has examined the impact of reactant flowrate, flow velocity, residence time, and flow regime (via the Reynolds number ([Re]) on DMHPFC performance. Balancing the competing demands of high residence time to improve Hydrogen peroxide reduction reaction (HPRR) rates with high flowrates to detach adsorbed O2, we identify a critical Re and Damkholer number (Da) to efficiently exclude O2 gas bubbles while maintaining large current densities during the operation of a DMHPFC. Reactant-transport engineering of the cathode flow field architecture and fuel flowrates mitigates parasitic hydrogen peroxide decomposition and oxygen reduction reactions and lessens cathode passivation by oxygen bubbles. DMHPCs fulfilling these criteria provide a power density of >500 mW cm-2 at 1.0 V compared to state-of-the-art polymer electrolyte membrane fuel cells (PEMFCs) that typically operate at 0.75 V. The high peak power density of 800 mW cm-2 at 1.1 V may offer a pathway to reduce fuel cell stack size for propulsion applications. Our work paves the way for such other liquid fuel cells with hydrogen peroxide as the oxidant and enabled with PMBI resulting in significantly improvement in the performance. Figure 1

Pt Single-Atom Catalysts Neighbouring Pt Nanoparticles with Synergistic Kinetics for Highly-Efficient Oxygen Reduction Reaction

Herein, we investigated the potential of downsizing Pt nanoparticles to single atom scale as a strategy to improve Pt utilization efficiency in electrocatalysts. We focused on Pt single atom catalysts anchored on high-surface area N-doped carbon[1-3], which have shown higher oxygen reduction reaction (ORR) activity than Pt nano-catalysts in fuel cell applications. However, the contribution of Pt nanoparticles in achieving these results has been questioned, and the selectivity of Pt SACs for ORR is still controversial. We prepared different types of carbon-supported Pt catalysts and used electrochemical measurements including rotating-ring disk electrode (RRDE) and hydrogen peroxide reduction reaction (HPRR) tests to elucidate the role of Pt SACs in carbon-supported Pt nano-catalysts. Additionally, we proposed a novel ORR mechanism based on in-situ X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations.

Dioxygen Reduction in Acetonitrile with Copper Pyridylalkylamine Complexes: The Influence of Acid Strength on the Catalytic Performance

AbstractThe pyridylalkylamine copper complex [Cu(tmpa)(L)]2+ has previously been proposed to reduce dioxygen via a dinuclear resting state, based on experiments in organic aprotic solvents using chemical reductants. Conversely, a mononuclear reaction mechanism was observed under electrochemical conditions in a neutral aqueous solution. We have investigated the electrochemical oxygen and hydrogen peroxide reduction reaction catalyzed by [Cu(tmpa)(L)]2+ in acetonitrile, using several different acids over a range of pKa. We demonstrate that strong acids lead to the loss of redox reversibility and to the destabilization of the copper complex under non‐catalytic conditions. Under milder conditions, the electrochemical oxygen reduction reaction (ORR) was shown to proceed via a mononuclear catalytic intermediate, similar to what we have previously observed in water. However, in acetonitrile the catalytic rate constants of the ORR are dramatically lower by a factor 105, which is caused by the unfavorable equilibrium of formation of [CuII(O2⋅−)(tmpa)]+ in acetonitrile. This results in higher catalytic rates for the reduction of hydrogen peroxide than for the ORR.

Mechanistic Investigations into the Selective Reduction of Oxygen by a Multicopper Oxidase T3 Site-Inspired Dicopper Complex.

Understanding how multicopper oxidases (MCOs) reduce oxygen in the trinuclear copper cluster (TNC) is of great importance for development of catalysts for the oxygen reduction reaction (ORR). Herein, we report a mechanistic investigation into the ORR activity of the dinuclear copper complex [Cu2L(μ-OH)]3+ (L = 2,7-bis[bis(2-pyridylmethyl)aminomethyl]-1,8-naphthyridine). This complex is inspired by the dinuclear T3 site found in the MCO active site and confines the Cu centers in a rigid scaffold. We show that the electrochemical reduction of [Cu2L(μ-OH)]3+ follows a proton-coupled electron transfer pathway and requires a larger overpotential due to the presence of the Cu-OH-Cu motif. In addition, we provide evidence that metal-metal cooperativity takes place during catalysis that is facilitated by the constraints of the rigid ligand framework, by identification of key intermediates along the catalytic cycle of [Cu2L(μ-OH)]3+ . Electrochemical studies show that the mechanisms of the ORR and hydrogen peroxide reduction reaction found for [Cu2L(μ-OH)]3+ differ from the ones found for analogous mononuclear copper catalysts. In addition, the metal-metal cooperativity results in an improved selectivity for the four-electron ORR of more than 70% because reaction intermediates can be stabilized better between both copper centers. Overall, the mechanism of the [Cu2L(μ-OH)]3+ -catalyzed ORR in this work contributes to the understanding of how the cooperative function of multiple metals in close proximity can affect ORR activity and selectivity.

Nickel-rare earth (Ce, Sm, Dy) alloy electrodes for hydrogen peroxide reduction in direct liquid fuel cells

• Nickel-rare earth (Ce, Sm, Dy) alloys (5 and 10 at.% RE) were prepared by arc melting. • Alloys structure, morphology, and composition were characterized by SEM/EDXS and XRPD. • LSV and CA evaluated Ni-RE alloys’ activity for hydrogen peroxide reduction reaction. • HPRR in alkaline media proceeds with 1.7 electrons exchanged at Ni 0.95 Ce 0.05 electrode. • Good performance of Ni 0.95 Ce 0.05 alloy suggests application in direct liquid fuel cells. Hydrogen peroxide (H 2 O 2 ), a reactive oxygen species, is an excellent alternative to oxygen as an oxidant for direct liquid fuel cells (DLFCs). To overcome problems related to scarcity and high cost of commonly used noble metal electrodes, nickel (Ni) and nickel-rare earth (RE = Ce, Sm, Dy) alloys are synthesised and evaluated as electrode materials for H 2 O 2 reduction reaction (HPRR) in alkaline media. These Ni-RE alloys (containing 5 and 10 at.% RE metal) are produced by arc melting and analysed by X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Voltammetric and chronoamperometric measurements are employed to assess the performance of the Ni-RE alloys for HPRR in 2 M NaOH solution. The Ni 0.95 Ce 0.05 alloy exhibits impressively high catalytic activity for HPRR, with a number of exchanged electrons of 1.7 and activation energy of 38 kJ mol -1 , suggesting its application as cathode material in DLFCs.

Developing in Situ Electrochemical Techniques to Understand Mechanisms of Bubble Formation at Aqueous Electrochemical Interfaces

Many electrochemical water treatment techniques (e.g. nitrate reduction, reactive oxygen species production, direct contaminant oxidation/reduction) rely on the electrochemical reactions that occur at the solid-liquid-gas triple-phase boundary layer, where gas species could be reactants, products, or undesired by-products. Developing foundational knowledge of the mechanisms by which surface bubbles form and how they impact chemical reactivity at surfaces would enhance the optimization and sustainability of electrified water treatment processes.The overall research goal is to develop in situ scanning electrochemical microscopy (SECM) to improve the microscopic understanding of how gas bubbles nucleate, form, grow, and migrate at solid–liquid interfaces. An important subset of gas-involving or gas-evolving, interfacial electrochemical reactions produces gas molecules dissolved in solution that can nucleate as small nanobubbles on electrode surfaces. These bubbles can grow to macroscopic sizes and interfere with chemical processes by blocking reactants from reaching the electrode-electrolyte interface, or by increasing turbulent mixing via leaving the surface. SECM is used to map the bubble formation mechanisms on the interface and to quantify the chemical species (reactant and product) concentration profile within the diffusion layer of the electrode surface. Here we will use oxygen reduction reaction (ORR) to hydrogen peroxide and nitrate reduction reaction (NO3RR) to ammonium as two model systems to investigate how SECM could help us understand chemical reaction mechanisms at aqueous electrochemical interfaces.

Ag-MnO2 composite materials (ferns-like structures) for hydrogen peroxide reduction in alkaline medium

• The Ag-MnO 2 Ferns-like were synthesized successfully via pulse electrodeposition (PE) method. • Ag-MnO 2 electrode was used as catalyst for hydrogen peroxide reduction reaction. • Ag-MnO 2 exhibits excellent electrocatalytic performance for H 2 O 2 reduction. In this study, Manganese dioxide (MnO 2 ) decorated with silver nanoparticles (Ag), was successfully synthetized by pulse electrodeposition (PE) onto fluorine doped tin oxide (FTO) substrate. The as-prepared Ag-MnO 2 /FTO sample has been characterized using X-ray diffraction, scanning electron microscopy and Impedance Spectroscopy. The micrographs revealed that the deposited film of silver nanoparticles is homogeneous and exhibits ferns-like microstructure. Electrochemical investigation indicates that the Ag-MnO 2 composite possess an excellent performance toward hydrogen peroxide (H 2 O 2 ) reaction in alkaline medium, this electrode could be used as cathode in feul cells.

High-performance metal (Au,Cu)–polypyrrole nanocomposites for electrochemical borohydride oxidation in fuel cell applications

Gold polypyrrole (AuPPy) and copper polypyrrole (CuPPy) nanocomposites were prepared by a simple one-step in situ oxidative polymerization of pyrrole monomer by Au3+ and Cu2+ ions. Owing to their characteristic physicochemical properties confirmed by optical and structural characterization methods, the behavior of these materials as electrocatalysts for borohydride oxidation reaction (BOR) was considered. BOR apparent activation energy was found to be 16 and 22 kJ mol−1 for AuPPy and CuPPy electrocatalyst, respectively. The stability of the two electrocatalysts was assessed by chronoamperometry. Moreover, fuel cell tests were carried out with AuPPy and CuPPy as anode electrocatalyst of a direct borohydride-peroxide fuel cell (DBPFC). Open circuit voltage (OCV) of 1.30 V was obtained with both AuPPy and CuPPy, with the OCV increasing to 1.45 V upon adding a small amount of carbon (AuPPy-C). The peak power density of a DBPFC with BOR at AuPPy-C anode and hydrogen peroxide reduction reaction at Pt cathode was found to be ca. 162 mW cm−2 at 65 °C.

From Ensemble Electrochemistry to Nano‐Impact Electrochemistry: Altered Reaction Selectivity

AbstractSelective electrochemical production of valued chemicals is of significant importance but remains a great challenge in chemistry. Conventional approaches for enhancing reaction selectivity focus on the improvement of the catalysts themselves. In this work, we systematically studied the reaction kinetics and mass transport behavior of LaNiO3 nanocubes (LaNiO3 NCs) catalyzed hydrogen peroxide reduction reaction (HPRR) at ensemble and single nanoparticle levels using nano‐impact electrochemistry (NIE). We find that the selectivity of HPRR was altered at individual random‐walk nanoparticles as compared to their ensemble counterpart without changing the reaction kinetics, due to the significantly enhanced mass transport at single nanoparticles. This discovery offers the scope of new catalytic approaches for engineering electrochemical reactions in general.

From Ensemble Electrochemistry to Nano‐Impact Electrochemistry: Altered Reaction Selectivity

Selective electrochemical production of valued chemicals is of significant importance but remains a great challenge in chemistry. Conventional approaches for enhancing reaction selectivity focus on the improvement of the catalysts themselves. In this work, we systematically studied the reaction kinetics and mass transport behavior of LaNiO3 nanocubes (LaNiO3 NCs) catalyzed hydrogen peroxide reduction reaction (HPRR) at ensemble and single nanoparticle levels using nano-impact electrochemistry (NIE). We find that the selectivity of HPRR was altered at individual random-walk nanoparticles as compared to their ensemble counterpart without changing the reaction kinetics, due to the significantly enhanced mass transport at single nanoparticles. This discovery offers the scope of new catalytic approaches for engineering electrochemical reactions in general.

Facile Synthesis of Low-Cost Copper-Silver and Cobalt-Silver Alloy Nanoparticles on Reduced Graphene Oxide as Efficient Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media.

Copper-silver and cobalt-silver alloy nanoparticles deposited on reduced graphene oxide (CuAg/rGO and CoAg/rGO) were synthesized and examined as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction reaction (HPRR) in alkaline media. Characterization of the prepared samples was done by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD), and scanning electron microscopy with integrated energy-dispersive X-ray spectroscopy (SEM-EDS). CuAg/rGO and CoAg/rGO nanoparticles diameter ranged from 0.4 to 9.2 nm. The Ag loading was ca. 40 wt.% for both electrocatalysts, with that for Cu and Co being 35 and 17 wt.%, respectively. CoAg/rGO electrocatalyst showed a Tafel slope of 109 mV dec−1, significantly lower than that for CuAg/rGO (184 mV dec−1), suggesting faster ORR kinetics. Additionally, a higher diffusion current density was obtained for CoAg/rGO (−2.63 mA cm−2) than for CuAg/rGO (−1.74 mA cm−2). The average value of the number of electrons transferred during ORR was 2.8 for CuAg/rGO and 3.3 for CoAg/rGO electrocatalyst, further confirming the higher ORR activity of the latter. On the other hand, CuAg/rGO showed higher peak current densities (−3.96 mA cm−2) for HPRR compared to those recorded for CoAg/rGO electrocatalyst (−1.96 mA cm−2).