Enhancement Of Electrocatalytic Activity Research Articles

Significant Enhancement of Electrocatalytic Activity of Nickel-Based Amorphous Zeolite Imidazolate Frameworks for Water Splitting at Elevating Temperatures

Significant Enhancement of Electrocatalytic Activity of Nickel-Based Amorphous Zeolite Imidazolate Frameworks for Water Splitting at Elevating Temperatures

Tailoring Spinel with Perovskite: Sr Substitution in the Perovskite Phase of CoFe2O4–LaCoO3 Nanocomposite for Oxygen Evolution and Methanol Oxidation in Alkaline Medium

CoFe2O4–La1−xSrxCoO3 (x = 0.2, 0.6, 0.8) composites have been synthesized using a two‐step, low‐temperature wet chemical approach that combines coprecipitation and sol–gel techniques. The composite materials have been physicochemically analyzed using Fourier‐transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscope. The electrocatalytic properties of the composite materials have been assessed in terms of their performance in oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. Cyclic voltammetry has been used for analyzing the redox behavior of the materials in 1 M KOH solution. The electrocatalytic activity of the materials has been assessed using anodic polarization curves on Ni substrate and the CoFe2O4–La0.2Sr0.8CoO3 film electrode demonstrates excellent activity, with current densities of 11.1 mA cm−2 for OER and 47.4 mA cm−2 for MOR at 650 mV. Also, the CoFe2O4–La0.2Sr0.8CoO3 film electrode has the maximum specific activity of 1.1 × 103 mA cm−2 g−1 at 650 mV toward OER. The electrodes’ stability has been assessed through chronoamperometric experiments and additional insight into the enhancement of electrocatalytic activity gained through the electrochemical surface area estimations using electrochemical impedance spectroscopy. From chronoamperometric experiment, it has been observed that the CoFe2O4–La0.2Sr0.8CoO3 film electrode attains stability within 114 s with a current density of 108.7 mA cm−2. Furthermore, the thermodynamic parameters, including the standard enthalpy of activation (ΔH°#), standard entropy of activation (ΔS°#), and standard electrochemical energy of activation (), have been estimated by anodic polarization curve recorded in KOH as well as KOH with CH3OH solutions at various temperatures.

Anodic surface treatment of nickel in eutectic ionic liquids based on choline chloride for electrochemical polishing and enhancement of electrocatalytic activity in hydrogen evolution reaction

The paper reports the impact of anodic potentiostatic treatment of nickel in two representatives of a new type of eutectic ionic liquids (deep eutectic solvents), ethaline and reline, which are eutectic mixtures of choline chloride with ethylene glycol and urea, respectively. The influence of anodic treatment on surface morphology, roughness coefficients, and electrocatalytic activity towards the hydrogen evolution reaction is characterized. It is demonstrated that the current densities of nickel anodic dissolution in reline are approximately an order of magnitude lower than in ethaline under all other identical conditions. Significant differences in the kinetics of nickel anodic dissolution and passivation during anodic polarization in ethaline and reline have been established, which may be attributed to both a substantial difference in the viscosity of these solvents and differences in the chemical nature and composition of the ions present in them. It is found that anodic treatment in ethaline, at certain potentials, results in electrochemical polishing of the surface, confirmed by a decrease in measured roughness coefficients, while anodic treatment in reline does not allow effective electropolishing and only surface etching (increase in roughness coefficients) is observed. Anodic potentiostatic treatment of nickel in both investigated deep eutectic solvents at specific electrode potential values significantly enhances the electrocatalytic activity of the surface towards the hydrogen evolution reaction in an alkaline environment. This finding can be utilized in the development of electrocatalytic materials for the electrolytic synthesis of green hydrogen.

Single-Particle Spectroelectrochemistry: Promoting the Electrocatalytic Activity of Gold Nanorods via Oxygen Plasma Treatment without Structural Deformation.

Understanding of the electrocatalytic activity enhancement in gold nanoparticles is still limited. Herein, we present the effect of the oxygen plasma treatment on the electrochemical activity of gold nanorods (AuNRs). Oxygen plasma treatment resulted in the blueshift and line width narrowing of the localized surface plasmon resonance (LSPR) spectra obtained from individual AuNRs immobilized on an indium tin oxide (ITO) surface. These changes can be attributed to increases in the surface charges of the AuNRs. The formation of a Au-ITO heterojunction provided structural stability to the immobilized AuNRs regardless of the duration of oxygen plasma exposure. The electrocatalytic oxidation of hydrogen peroxide (H2O2) was induced by increases in the free-electron densities on the surfaces of these AuNRs owing to oxygen plasma treatment, and Au did not dissolve under the experimental conditions. However, the potential-dependent LSPR spectra of the individual AuNRs showed similar patterns of LSPR behavior, irrespective of the duration of oxygen plasma treatment and the concentration of H2O2. Therefore, this study based on single-particle spectroelectrochemistry and cyclic voltammetry improves the understanding of the role of oxygen plasma treatment in promoting the catalytic activity of structurally stable AuNRs immobilized on an ITO surface.

Incorporating a built-in electric field into a NiFe LDH heterojunction for enhanced oxygen evolution and urea oxidation.

Herein, a N-doped carbon-supported Co and NiFe LDH (Co-NC@NiFe LDH) array was developed, which demonstrated superior catalytic activities for both the OER and UOR in an alkaline medium. The intrinsic electron transfer is effectively regulated by the construction of a built-in electric field, which reduces the reaction energy barrier and consequently leads to a significant enhancement in electrocatalytic activity.

Engineering of heterointerface of ultrathin carbon nanosheet-supported CoN/MnO enhances oxygen electrocatalysis for rechargeable Zn–air batteries

Designing bifunctional electrocatalysts with outstanding reactivity and durability towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has remained a long-term aim for metal-air batteries. Achieving the high level of fusion between two distinct metal components to form bifunctional catalysts with optimized heterointerfaces and well-defined morphology holds noteworthy implications in the enhancement of electrocatalytic activity yet challenging. Herein, the fabrication of numerous heterointerfaces of CoN/MnO is successfully realized within ultrathin carbon nanosheets via a feasible self-templating synthesis strategy. Experimental results and theoretic calculations verify that the interfacial electron transfer from CoN to MnO at the heterointerface engenders an ameliorated charge transfer velocity, finely tuned energy barriers concerning reaction intermediates and ultimately accelerated reaction kinetics. The as-prepared CoN/MnO@NC demonstrates exceptional bifunctional catalytic performance, excelling in both OER and ORR showcasing a low reversible overpotential of 0.69 V. Furthermore, rechargeable liquid and quasi-solid-state flexible Zn-air batteries employing CoN/MnO@NC as the air-cathode deliver remarkable endurance and elevated power density, registering values of 153 and 116 mW cm−2 respectively and exceeding Pt/C + RuO2 counterparts and those reported in literature. Deeply exploring the effect of electron-accumulated heterointerfaces on catalytic activity would contribute wisdom to the development of bifunctional electrocatalysts for rechargeable metal-air batteries.

Controlled synthesis of efficient novel Cr0.2Co2.8O4–MoO3 nanocomposites for high-performance O2-evolution and methanol oxidation in alkaline medium

The world of electrochemical devices is constantly pushing the boundaries to what's possible, and nanocomposites are becoming crucial electrocatalysts for enhancing electrochemical performance. In this study, the affect in electrochemical behaviour on altering constituent amount in the electrocatalysts has been discussed. For this we synthesized a novel Cr0.2Co2.8O4–MoO3 nanocomposites with varying constituent proportional amount using simple low-temperature route. The formation and the physicochemical properties have been investigated by Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Raman, Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) techniques. The XRD and XPS patterns confirms the nano crystalline structures and compositional difference in metal cations distribution respectively. Results from Cyclic Voltammetry (CV), Tafel experiments, Chronoamperometry and Electrochemical impedance Spectroscopy (EIS) shows the ratio of Cr0.2Co2.8O4 to MoO3 strongly affects the catalytic performance in both oxygen evolution and methanol oxidation reactions. The observed enhancement in electrocatalytic activity can be ascribed to the combined impact of the two materials facilitating the electron transfer process by increasing the number of active sites and thereby. Amongst different synthesized electrocatalysts the one with 1:4 composition exhibited not only the highest Specific activity of 2.5 × 103 mA cm−2/g at 700 mV towards OER but also retains maximum current showing their highest stability.

Development of Different Kinds of Electrocatalyst for the Electrochemical Reduction of Carbon Dioxide Reactions: An Overview.

Significant advancements have been made in the development of CO2 reduction processes for applications such as electrosynthesis, energy storage, and environmental remediation. Several materials have demonstrated great potential in achieving high activity and selectivity for the desired reduction products. Nevertheless, these advancements have primarily been limited to small-scale laboratory settings, and the considerable technical obstacles associated with large-scale CO2 reduction have not received sufficient attention. Many of the researchers have been faced with persistent challenges in the catalytic process, primarily stemming from the low Faraday efficiency, high overpotential, and low limiting current density observed in the production of the desired target product. The highlighted materials possess the capability to transform CO2 into various oxygenates, including ethanol, methanol, and formates, as well as hydrocarbons such as methane and ethane. A comprehensive summary of the recent research progress on these discussed types of electrocatalysts is provided, highlighting the detailed examination of their electrocatalytic activity enhancement strategies. This serves as a valuable reference for the development of highly efficient electrocatalysts with different orientations. This review encompasses the latest developments in catalyst materials and cell designs, presenting the leading materials utilized for the conversion of CO2 into various valuable products. Corresponding designs of cells and reactors are also included to provide a comprehensive overview of the advancements in this field.

Cerium guided site-selective crystal disorder engineering of MIL-88B(Ni) frameworks for electrocatalysis offering high-performance water oxidation

Engineering the degree of crystallinity is an attractive route to expose unsaturated coordinative metal nodes that act as active electrocatalytic sites in metal-organic frameworks (MOFs). Herein, we develop a novel strategy to induce site-selective disordering of the crystalline structure of MIL88B(Ni) frameworks via Ce-doping, resulting crystalline/amorphous heterostructures. X-ray diffraction and electron microscopy analyses reveal that Ce-rich spherical regions in the framework are amorphous while Ce-deficient flat sheets are crystalline. Comparatively, an optimally Ce-doped MIL-88B(Ni)/NF(nickel foam) anode exhibits significantly lower overpotentials (η) of 205, 290, 410 and 450 mV to drive the oxygen evolution reaction (OER) under current densities of 10, 100, 1000 and 2000 mAcm−2, respectively with a superior kinetic of 46.09 mVdec−1 and a larger turnover frequency (TOF@η = 330 mV) of 0.36 s−1. DFT calculations support the experimentally observed Ce3+ ion doping effect in inducing site-selective crystal disorder on MIL-88B(Ni) framework structure, and hence on the OER electrocatalytic activity enhancement. In addition to the remarkably high OER performance, the optimized Ce-doped MIL-88B(Ni)/NF anode exhibits superbly enhanced electrochemical durability over 146 h against industrially relevant high biases of up to 1000 mAcm−2 in 1.0 M KOH solution, thus demonstrating that Ce-doped MIL88B(Ni)/NF is a highly promising industrially relevant high-performance anode material for electrocatalyzing the OER.

Cu-Ag bimetallic nanostructures with high glucose sensing performance fabricated by a scalable and reproducible method

A scalable and repeatable synthetization method is introduced to fabricate Cu-Ag bimetallic nanostructures as a stable, robust, fast-response and enzyme-free glucose sensor. Cu nanocolumns were constructed on the FTO substrate using the glancing angle deposition (GLAD). Then a thin layer of Ag is deposited on the Cu nanocolumns through a galvanic replacement reaction. The Cu-Ag nanostructures with different morphologies were developed by tuning the concentration and the reaction time of the galvanic replacement process. Various electrochemical characterizations, including cyclic voltammetry and electrochemical impedance spectroscopy (EIS), were performed to determine the superior electrocatalytic activity of the electrodes. The results reveal that the superior electrocatalytic performance toward glucose oxidation was achieved with Cu-Ag fabricated under the AgNO3 concentration of 5 mM and with a reaction time of 30 s. The sensor exhibits a fast response of ∼2 s with an excellent sensitivity of 3802 and 712 μAcm−2 mM−1 in two wide linear ranges of 0.01–3 mM and 3–8 mM and an optimum potential of 0.65 V. The proposed Cu-Ag sensor showed considerable enhancement of electrocatalytic activity compared to Cu or Ag monometallic structures due to the synergistic effect. In addition, the current bimetallic sensor regarding its outstanding precision and its reproducibility provides a promising method for large scale fabrication of non-enzymatic glucose sensors.

Ba-doped LaCoO3 perovskite as novel bifunctional electrocatalyst for zinc–air batteries

Developing efficient non-noble metal bifunctional cathode catalysts to accelerate the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is still a major challenge for zinc–air batteries (ZABs). In the present study, a series of La1−xBaxCoO3 (x = 0, 0.05, 0.10, 0.15, 0.20) perovskite-type oxides were prepared via self-propagating high-temperature synthesis and evaluated as the bifunctional electrocatalytic activity for ZABs. Among the samples, La0.85Ba0.15CoO3 showed the best bifunctional catalytic activity, in which the Eonset of ORR at 0.1 mA cm−2 and the Ej of OER at 10 mA cm−2 in 0.1 M KOH solution were 0.829 and 1.685 V vs.RHE, respectively. Besides, the La0.85Ba0.15CoO3 catalyst was evaluated as an air electrode for ZABs, displaying a high power density of 116.2 mW cm−2 at the current density of 233.8 mA cm−2 and a stable charge–discharge voltage gap of 0.98 V after 1200 cycles, with superior cycling stability over 200 h. Characterization analysis revealed that the enhancement of bifunctional electrocatalytic activity was attributed to the larger specific surface area and increase in oxygen vacancy. Thus, the Ba-doped LaCoO3 material is a promising bifunctional electrocatalyst for ZABs.

Electrocatalytic barium-oxide decorated MWCNT amperometric sensor for the quantification of anesthetic drug Procaine

Procaine hydrochloride (P.HCl) is one of the earliest and most well-established local anesthetic drugs used in medicine. Though it is employed frequently for effective clinical nerve blocks during surgeries, its immoderate administration has often shown reports of systemic toxicity. To prevent such repercussions, developing a sensor for the drug is crucial to enable real-time monitoring of the drug and assist in quality control procedures during its industrial preparations. Thus, in this work, we have fabricated a simple yet highly selective and sensitive amperometric sensor for P.HCl detection based on a Barium-oxide multi-wall carbon nanotube-modified carbon paste electrode (BaO-MWCNT/CPE). Herein, we have adopted a novel approach devoid of sophisticated procedures and pretreatments for rapidly determining P.HCl. Furthermore, experimental conditions, including supporting electrolytes, pH, and scan rate, were optimized to achieve a well-defined P.HCl anodic peak current at 631 mV, which is lower than the previously reported peak potentials, indicating an advantage of reduced overpotential. Besides, a striking 66-fold rise in current responsiveness to P.HCl was achieved upon modification with BaO-MWCNT. Such an intense signal enhancement upon electrode modification compared to bare CPE was due to the strong electrocatalytic feature of BaO-MWCNT, which was verified using surface morphology studies with scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Additionally, the charge transfer kinetics analyzed via electrochemical impedance spectroscopy (EIS) justified the enhancement of electrocatalytic activity upon electrode modification. The developed sensor exhibited a remarkable analytical performance over a wide linear dynamic range of 2.0–100.0 µM with a detection limit of 0.14 µM. Moreover, a significant merit of this sensor is its excellent selectivity towards P.HCl even in the presence of various common interferants. Finally, the versatility of the sensor was further validated by implementing it for the trace analysis of urine and blood serum real samples.

Patulin-imprinted origami 3D-ePAD based on graphene screen-printed electrode modified with Mn–ZnS quantum dot coated with a molecularly imprinted polymer

We developed a novel, compact, three-dimensional electrochemical paper-based analytical device (3D-ePAD) for patulin (PT) determination. The selective and sensitive PT-imprinted Origami 3D-ePAD was constructed based on a graphene screen-printed electrode modified with manganese-zinc sulfide quantum dots coated with patulin imprinted polymer (Mn–ZnS QDs@PT-MIP/GSPE). The Mn–ZnS QDs@PT-MIP was synthesized using 2-oxindole as the template, methacrylic acid (MAA) as a monomer, N,N′-(1,2-dihydroxyethylene) bis (acrylamide) (DHEBA) as cross-linker and 2,2′-azobis (2-methylpropionitrile) (AIBN) as initiator, respectively. The Origami 3D-ePAD was designed with hydrophobic barrier layers formed on filter paper to provide three-dimensional circular reservoirs and assembled electrodes. The synthesized Mn–ZnS QDs@PT-MIP was quickly loaded on the electrode surface by mixing with graphene ink and then screen-printing on the paper. The PT-imprinted sensor provides the greatest enhancement in redox response and electrocatalytic activity, which we attributed to synergetic effects. This arose from an excellent electrocatalytic activity and good electrical conductivity of Mn–ZnS QDs@PT-MIP, which improved electron transfer between PT and the electrode surface. Under the optimized DPV conditions, a well-defined PT oxidation peak appears at +0.15 V (vs Ag/AgCl) using 0.1 M of phosphate buffer (pH 6.5) containing 5 mM K3Fe(CN)6 as the supporting electrolyte. Our developed PT imprinted Origami 3D-ePAD revealed excellent linear dynamic ranges of 0.001–25 μM, with a detection limit of 0.2 nM. Detection performance indicated that our Origami 3D-ePAD possesses outstanding detection performance from fruits and CRM in terms of high accuracy (%Error for inter-day is 1.11%) and precision (%RSD less than 4.1%). Therefore, the proposed method is well-suited as an alternative platform for ready-to-use sensors in food safety. The imprinted Origami 3D-ePAD is an excellent disposable device with a simple, cost-effective, and fast analysis, and it is ready to use for determining patulin in actual samples.

Engineering high-spin state cobalt cations in spinel ZnCo2O4 for spin channel propagation and electrocatalytic activity enhancement in Li-O2 battery

Spinel zinc cobalt oxide (ZnCo2O4) is considered as the promising electrocatalyst for the electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, theoretical calculations uncovered that the presence of low-spin (LS) state cobalt cations impedes the electrocatalytic activity of ZnCo2O4 because the t2g6eg0 configuration yields purely localized electronic structure with poor binding affinity with reaction intermediate. By regulating the spin state of cobalt cations in ZnCo2O4, spin-selected charge transfer is boosted during ORR/OER processes due to the propagated spin channel, thus causing abundant active sites for intermediates adsorption. Experimental results show that increasing calcination temperature during the synthesis process is an operable method to fabricate high-spin (HS) cobalt cations in ZnCo2O4. And the Li-O2 battery with ZnCo2O4 containing high-spin cobalt cations shows remarkably low overpotential of only 0.45 V and excellent durability of more than 800 h. This work underlines the critical role of the electron spin state in facilitating oxygen redox reactions on transition metal oxides.

Fabrication of Graphene Oxide-Decorated Mesoporous NiFe2O4 as an Electrocatalyst in the Hydrogen Gas Evolution Reaction

An electrocatalyst for the hydrogen evolution reaction has been successfully synthesized from graphene oxide (GO) decorated with the mesoporous NiFe2O4. A high catalytic activity performance was reached by using the GCE surface as a conductor, and the synthesized composite contained GO/NiFe2O4. Based on the results, the as-prepared electrocatalyst exhibited a high overpotential for the HER reaction of 36 mV vs. RHE at a 10 mA current density, with an electrochemical active surface area (ECSA) of 3.18 × 10−4 cm2. Additionally, the electrocatalyst demonstrated a considerably good performance after the 9000 s stability test. It is believed that such an enhancement in electrocatalytic activity was due to the synergistic effect between the unique porosity feature of the mesoporous NiFe2O4, which may provide a more active surface, and the high conductivity of the GO.

Dual Function of Hypo-d-electronic Transition Metals in the Brewer Intermetallic Phase for the Highly Efficient Electrocatalytic Hydrogen Evolution Reaction in Alkaline Electrolytes

Reported are the synthesis, material characterization, and electrocatalytic hydrogen evolution reaction (HER) in acid and alkaline electrolytes for the Brewer intermetallic phase, Nb6Co7 and Mo6Co7. It was realized that the overpotential at a current density of 10 mA/cm2 (η10) for Nb6Co7 (η10 = 62 mV) and Mo6Co7 (η10 = 143 mV) are both much lower than that of using a single Co metal (η10 = 253 mV) in alkaline electrolytes. The enhancement of electrocatalytic HER activity of Nb6Co7 and Mo6Co7 can be attributed to the hypo-hyper-d-electronic interaction between Nb/Mo and Co elements. Based on the result of density functional theory calculation, alloying between Nb/Mo and Co elements will increase the antibonding state population of the Co-Co bond near the Fermi level (EF), which induces the synergistic effect to influence the adsorption energy of the H atom (ΔGH) on the surface of Nb6Co7 and Mo6Co7. Moreover, the role of the Nb element is not only a simple electron donor but is also an anchor position for the OH molecule (i.e., dual function) due to the bonding character of the Nb-Co bond near EF. It can reduce the OH position effect as well as the activation energy for water dissociation, which rationalizes the high and robust HER performance of Nb6Co7 to that of commercial Pt/C (η10 = 67 mV) in alkaline electrolytes.

Electrocatalytic water splitting by a low crystallinity CeOx@Co3O4 heterostructure

The development of bifunctional electrocatalysts with high activity and low cost is urgent but remains challenging for water splitting. Here, the core–shell heterostructure between ultrasmall ceria nanoparticles with low crystallinity and Co3O4 nanowires (CeOx@Co3O4) is successfully constructed via rapid electrodeposition. Systematic studies revealed that ultrasmall ceria with low crystallinity can induce the rich unsaturated active sites, accelerate the charge transfer and provide the strong electronic interaction between Co3O4 and ceria. As a result, a strong enhancement of electrocatalytic activity at the CeOx@Co3O4 heterostructure is reported with low overpotential (252 and 106 mV at 10 mA cm−2) and small Tafel slopes (41 and 106 mV dec−1) for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. The electrolyzer based on CeOx@Co3O4 heterostructure shows a low cell voltage of 1.57 V and excellent stability to attain a current density of 10 mA cm−2. This work provides a valuable reference for the preparation of bifunctional electrocatalysts with low cost and high activity.

A facile synthesis of polyaniline-WO3 hybrid nanocomposite for enhanced dopamine detection

In this work, an enhanced electrochemical sensor for dopamine (DA) is constructed based on the tungsten nanoparticles with a polyaniline nanocomposite (PANI-WO3) coated glassy carbon electrode (GCE). The obtained PANI-WO3/GCE film displayed a notable enhancement of electrocatalytic activity for DA with significant redox property. The PANI-WO3/GCE sensors displayed excellent detection for DA with a detection limit of 0.139 μmol/L revealed a good linear relationship with concentration from 20 − 300 µM (S/N = 3). PANI and WO3 composite shows significant electrochemical oxidation of DA.

Copper-Decorated Ti3C2Tx MXene Electrocatalyst for Hydrogen Evolution Reaction

It remains a formidable challenge to prepare an economical and stable electrocatalyst for hydrogen evolution reaction using non-precious metals. In this study, MXene (Ti3C2Tx) nanosheets were prepared by high-energy ultrasound treatment, and Cu nanoparticles were prepared by NaBH4 as a reducing agent. Then, the electrocatalyst Cu/Ti3C2Tx, suitable for hydrogen evolution reaction (HER), was prepared by supporting Cu with Ti3C2Tx. The structure, morphology, crystal phase and valence state of the obtained catalyst were determined by a variety of characterization analysis methods, and the influence of these properties on the catalytic performance is discussed here. The results of Brunner–Emmet–Teller (BET) showed that Ti3C2Tx can effectively inhibit Cu agglomeration. Results of Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) showed that Cu has metallic and oxidized states. X-ray Photoelectron Spectroscopy (XPS) further revealed the existence of multivalent states in Cu, which would contribute to the formation of electron transfer channels and the enhancement of electrocatalytic activity. In addition, the Cu/Ti3C2Tx catalyst has strong hydrophilicity, as measured by contact angle, which is conducive to HER. Ti3C2Tx has acceptable electrocatalytic hydrogen evolution performance: under alkaline conditions, when the current density is 10 mA cm−2, HER overpotential is as low as 128 mV and the Tafel slope is as low as 126 mV dec−1. Meanwhile, Ti3C2Tx showed adequate stability for HER (94.0% of the initial mass activity after 1000 CV cycles). This work offers insights into the development of high-performance non-precious metal-based catalysts to achieve the high performance of HER in alkaline electrolytes.

Asymmetrically coupled Co Single-atom and Co nanoparticle in Double-shelled Carbon-based nanoreactor for enhanced reversible oxygen catalysis

Simultaneous construction of size-asymmetric metal single atoms and nanoparticle active sites in advanced and robust carrier materials is particularly important yet challenging for efficient reversible oxygen catalysis. Herein, a facile “chemical etching/in-Situ capture” synthesis strategy was developed to fabricate a unique double-shelled carbon-based nanobox integrated with size-asymmetric Co single-atom (CoSA) and metallic Co nanoparticle (CoNP) moiety. As expected, this well-managed catalyst product yielded remarkable bifunctional electrocatalytic performances in alkaline electrolytes, with a decent half-wave potential of 0.886 V for oxygen reduction reaction (ORR) and a small overpotential of 341 mV at 10 mA/cm2 for oxygen evolution reaction (OER). Besides, this nanobox catalyst served as a cost-effective and efficient oxygen electrode in the assembled rechargeable ZABs, exceeding the mixed electrocatalyst of expensive Pt/C-RuO2, in terms of the elevated peak power density of 239 mW/cm2, the promoted specific capacity of 770 mAh/gZn, as well as the appreciable charge–discharge cycle stability. Theoretical calculations revealed that the strong interaction between the delicate CoSA site and CoNP phase, could effectively optimize the adsorption and desorption energy barriers of reaction intermediates on the designed catalyst surface, thus achieving synergistic enhancement of electrocatalytic activity towards ORR and OER. This finding affords a feasible and effective strategy to achieve highly active and durable bifunctional catalysts for both fundamental research and practical rechargeable ZABs applications.