Galvanic Displacement Research Articles

Ultralow Ru-doped NiFe catalyst on stainless-steel fibers for enhanced oxygen evolution reaction in anion-exchange membrane water electrolysis

Designing high-performance, stable electrodes for the oxygen evolution reaction (OER) is essential for anion-exchange membrane water electrolysis (AEMWE) in industrial-scale hydrogen production. AEMWE has not yet been commercialized due to the high cost of precious metal catalysts and unsatisfactory performance of non-precious metal catalysts. Although various anodes are being developed to replace expensive Ir-based catalysts, low-cost catalysts that demonstrate a balance of performance and stability remain limited. In the present study, we fabricated a NiFe catalyst on a corrosion-resistant stainless-steel fiber paper substrate using a simple electrodeposition method and introduced small amounts of Ru via galvanic displacement. In half-cell tests, an enhanced overpotential of 229 mV was observed for the Ru-NiFe/SS anode at 10 mA/cm2. Using Ru-NiFe/SS as an anode for OER in AEMWE assembled with a commercial Pt/C cathode exhibited high performance with a current density of 8.73 A cm−2 (at 2.05 Vcell and 80℃). Long-term stability tests also showed that the Ru-NiFe/SS anode had higher stability than commercial IrO2 electrodes at 1 A cm−2 and 80℃ for 50 h. Therefore, Ru-NiFe/SS can be considered an alternative to conventional Ir-based electrodes to reduce hydrogen production costs.

Electrocatalytic behavior of a mixed catalyst PdCu/Ag synthesized using electrochemical co-deposition and galvanic displacement

Electrocatalytic behavior of a mixed catalyst PdCu/Ag synthesized using electrochemical co-deposition and galvanic displacement

Infiltrated electroless deposition of gold nanoparticles on porous Prussian blue-Fe2O3 hetero-microstructures for environmental remediation applications: A novel infiltration strategy to form 3-D nano-catalytic networks

Metal and metal oxide nanocomposites are promising candidates for heterogeneous catalytic applications. In this regard, most of the metal oxide inner core volume remains as a dead volume, not participating in the catalysis, only the metal/metal oxide hetero-junctions available at the surfaces are involved in the catalysis. Herein, we report a novel strategy for the infiltration of gold nanoparticles into the inner core of 3D-porous Prussian blue/Fe2O3 hetero-microstructures (PBFHM-Au) beyond its outer surface to form an advanced heterogeneous catalyst for the environmental remediation applications. The porosity of the Prussian blue microstructures is thermally tuned for the infiltration of gold ion precursor into the inner core volume of Prussian blue/Fe2O3 hetero-microstructures to facilitate the galvanic displacement reaction between Fe and Au to enlarge the lattice shell and form Au nanoparticle 3D networks throughout the PBFHM. Notably, the resulting PBFHM-Au2 shows enhanced structural stability electron transfer kinetics and catalytic activity in comparison with the only surface-attached Au/Fe2O3 composite. The obtained PBFHM-Au2 catalyst demonstrates remarkable catalytic activity for Rhodamine-B dye degradation with rate constant (k = 3.47 × 10−2 s−1) and p-nitrophenol reduction reactions with rate constant (k = 1.199 × 10−1 s−1).

Electrocatalysis of hydrogen and oxygen electrode reactions in alkaline media by Rh-modified polycrystalline Ni electrode

Developing novel electrocatalysts for energy conversion applications is of utmost importance for reaching the energy security of modern society. Here we present a comprehensive investigation of rhodium-modified polycrystalline nickel as an electrocatalyst for hydrogen and oxygen electrode reactions in alkaline media. The surface modification of nickel electrodes was achieved by facile galvanic displacement (up to 30 s) from a highly concentrated acidic Rh3+ solution. The results demonstrate a significant enhancement in the electrocatalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on the Rh-modified Ni electrodes, positioning galvanic displacement as a viable approach to engineering advanced electrocatalysts for clean energy applications. On the other hand, the hydrogen oxidation (HOR) and oxygen reduction reaction (ORR) activities of the Rh-modified electrodes are lower compared to polycrystalline platinum. It is suggested that semiconducting Rh2O3 has a detrimental role on the HOR and ORR performance, while the activities of HER and OER, dominantly taking place on metallic Rh and conductive RhO2, are very high. This research sheds light on the mechanisms underlying the enhanced electrode kinetics on Rh-modified Ni electrodes and provides insights into the development of efficient and cost-effective electrocatalysts for renewable energy technologies.

Fabrication of Al/Ni core–shell pigments via galvanic displacement and their application in radar-infrared compatible stealth coatings

The Al/Ni magnetic core–shell pigments were successfully synthesized in this study using the galvanic displacement method. A dense nickel shell was formed on the surface of a flake Al pigment (Al:Ni2+ = 1:0.5), resulting in a decrease in its lightness by 9 units while only slightly increasing the average infrared emissivity by 0.1 compared with the uncoated flake Al pigments. And it also exhibited soft magnetic characteristics, with a saturated magnetization value of 4.5 emu/g. Moreover, the impact of Al/Ni core-shell pigments on the infrared-radar stealth performance of the target was investigated based on the structure of “low-emissivity coating (LEC) + radar absorbing coating (RAC)”. The results showed that the emissivity of Al/Ni composite coatings maintained a low infrared emissivity (ε ≤ 0.23). The introduction of Ni shell improved the impedance matching between the Al/Ni coating and free space, allowing greater penetration of microwaves into the LEC and improving radar stealth performance of materials. The Al/Ni composite coatings (Al:Ni2+ = 1:0.5, the thickness of RAC:1.2 mm, and LEC: 60 μm) exhibited an extended effective absorption bandwidth (Reflection loss (RL) ≤ −10 dB) from 2.6 to 4.25 GHz and an enhancement of the average RL from −6.43 to −7.1 dB in the range of 2–18 GHz compared to the RAC. Consequently, the Al/Ni magnetic core–shell pigments can be used as novel low-emissivity pigments for infrared-radar compatible stealth research.

Ni-Pt Core-Shell Formation via Spontaneous Galvanic Displacement Reaction at Boron Doped Diamond Electrodes for Ammonia Oxidation Reaction

Ammonia is a major environmental pollutant that is highly toxic and may cause unfavourable effects to the human body, even in low concentrations. As a result, the monitoring and elimination of NH3 has been an important topic worth exploring in depth. Moreover, ammonia can be a suitable fuel cell source because its theoretical electrical charge density is relatively high and it’s possible to take this advantage by converting ammonia to nitrogen and electrical energy via the ammonia oxidation reaction (AOR). This reaction requires a catalyst to decrease the energy barrier that prevents the molecule from reacting and transforming into nitrogen.Ammonia electro-oxidation reaction has been paid much attention in recent years because it is widely used in various fields. However, the electro-oxidation of ammonia is a complex process, especially the reaction intermediate has a slow toxic effect on the electrode. To reduce the catalyst poisoning by the absorption of intermediate, the constituent and structure of the catalysts must be deeply researched.Herein, a bimetallic Pt–Ni catalyst-modified boron-doped diamond (BDD) electrode was done via spontaneous galvanic displacement reaction for the ammonia oxidation reaction. The synergistic properties may include the promotion of low-temperature oxidation, improvement of the oxidation resistance, and increased catalytic efficiency. BDD was used as the electrode substrate in this work due to its excellent resistance to corrosion and good stability over time in a highly corrosive environment. First, nickel was electro-deposited through chronoamperometry on the BDD electrode surface at a potential of -1.1V vs Ag/AgCl in 0.1M KClO4 & 5mM Ni (NO3)2.6H2O aqueous solution. Second, platinum was deposited on the nickel particles on the BDD electrode surface through a spontaneous galvanic displacement reaction by a redox process which involves the nickel oxidation and Pt2+ reduction, using a K2PtCl4 precursor on the BDD surface while forming a core shell structure. Lastly, the Pt-Ni deposited on the BDD surface was then characterized through different techniques such as XPS, SEM, EDS, and Raman before and after the ammonia oxidation reaction.Preliminary studies of the behaviour of BDD electrodes in the presence of Ni and Pt have been carried out to determine the electrochemical conditions at which the substrate works with these metal salts. The results found with these studies will show how Pt-Ni catalyst will improve AOR in alkaline media.

Cu-Co Bimetallic Catalyst-based Electrochemical Sensing Platform for Determination of Bisoprolol in Clinical Samples.

Bisoprolol (BIS) is a selective beta-blocker. It has been successfully used to treat hypertension and angina pectoris. An overdose of BIS can lead to serious complications. An overdose is a medical emergency that requires immediate medical attention to overcome the adverse effects of the overdose. Hence, sensitive, reliable, and cost-effective methods are required for the determination of BIS. In this work, a new electrochemical sensing platform based on a bimetallic catalyst was developed for the determination of BIS. The Cu-Co nanocatalyst was easily synthesized by galvanic displacement onto a carbon paste electrode (CPE). Then, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and cyclic voltammetry (CV) were utilized for the characterization of the Cu-Co catalyst. The galvanic displacement of Cu metal significantly affected the electro-catalytic behavior of the Cu-Co catalyst and the Cu-Co/CPE electrode displayed a very sensitive and accurate response towards BIS. Under optimized conditions, the response was linear in the 3 to 120 μM concentration range, sensitivity of 631.1 μA mM-1 and a detection limit of as low as 0.4 μM using cyclic voltammetry. The simple proposed method was also successfully employed in the analysis of BIS in biological and pharmaceutical samples. The advantages of Cu-Co/CPE are its fast and simple manufacturing and the possibility of a repeated surface regeneration of the sensing platform, as well as its application for the detection of BIS in tablets and biological samples, making Cu-Co significant promise for use in clinical diagnostics. Besides, the synthesized catalysts showed excellent reusability and stability. The presence of Cu metal due to galvanic displacement increased the sensitivity. These findings suggest that the new nanocatalyst has potential applications in sensors and electronics.

Development of ternary hybrid composites of transition metal and noble metal-based heterostructures: Ultrasensitive simultaneous electrochemical detection of bisphenol A and bisphenol S in food samples

Bisphenols threaten human health and sensitive detection is crucial. The present study aims to develop ternary composites of copper metal-organic framework (Cu-MOF) with AuAg microstructures. The composite structure was formed by a galvanic displacement reaction and confirmed using SEM. A binder-free catalyst was used to study the electrochemical redox reaction of bisphenol A (BPA) and bisphenol S (BPS); an irreversible cyclic voltammetric signal at +0.70 V and + 0.91 V (vs. Ag/AgCl), in the dynamic range of 20 nM to 2.0 mM, and 10 nM to 1.0 mM, with limits of detection of 2.9 nM, and 3.2 nM (S/N = 3) was obtained. Practical analysis was applied to frozen tomatoes, tuna fish, milk powder, PET bottles, raw milk, and urine samples with a recovery rate of 94.00–100.80% (n = 3). Voltammetric results were validated using HPLC detection with high precision. The sensor is a promising alternative platform for measuring BPA in food samples.

Ultrasensitive electrochemical sensors based on Cu and Cu@Ag nanorods for simultaneous heavy metal detection

This work reports the development of ultrasensitive miniaturized electrochemical device for heavy metal sensing. A laser engraver based patterning of fluorine-doped tin oxide (FTO) sheet was done to draw an etched pattern forming a miniaturized 3-electrode configuration. A layer of Ag/AgCl ink served as pseudo-reference electrode. The sensing electrode was coated using low-cost Cu nanorods (CuNRs) grown radially along the {110} surface with aspect ratio of 8.0 and Cu@Ag core-shell nanorods (Cu@AgNRs) formed via galvanic displacement for simultaneous electrocatalytic detection of heavy metal ions (Pb(II), Cd(II), Hg(II), and Zn(II)) present in water. The electroactive surface area of the prepared devices is 0.026, 0.093 and 0.125 cm2 for bare FTO, CuNRs/FTO and Cu@AgNRs/FTO, respectively. Bimetal Cu@AgNRs/FTO sensor exhibited the lowest limit of detection of 1, 2, 5 and 6 nM, respectively, detecting Cd(II), Pb(II), Zn(II), and Hg(II) ions, and it was 2, 2, 3 and 4 nM, respectively, for simultaneous detection of Zn(II), Pb(II), Cd(II) and Hg(II). The Cu@AgNRs/FTO based device showed distinct peak-to-peak separation by 0.40, 0.25 and 0.51 V for Zn(II)-Cd(II), Cd(II)-Pb(II) and Pb(II)-Hg(II), respectively. This device was highly sensitive (583.6–1261.8 μA․μM−1․cm−2) for heavy metal detection over CuNRs/FTO (15.9–107.4 μA․μM−1․cm−2). The Cu@AgNRs/FTO based sensors demonstrated good reproducibility (relative standard deviation ≤ 5%) with recovery (>90%) in the case of all target heavy metals simultaneously present in environmental water samples. Hence, the Cu nanorods based miniaturized sensing platforms developed in the present study for simultaneous heavy metal detection are potential low-cost alternatives providing a repeatability of upto 4 cycles unlike the commercial screen-printed electrodes.

Driving inward growth of lithium metal in hollow microcapsule hosts by heteroatom‐controlled nucleation

AbstractThe application of Li metal anodes in rechargeable batteries is impeded by safety issues arising from the severe volume changes and formation of dendritic Li deposits. Three‐dimensional hollow carbon is receiving increasing attention as a host material capable of accommodating Li metal inside its cavity; however, uncontrollable and nonuniform deposition of Li remains a challenge. In this study, we synthesize metal–organic framework‐derived carbon microcapsules with heteroatom clusters (Zn and Ag) on the capsule walls and it is demonstrated that Ag‐assisted nucleation of Li metal alters the outward‐to‐inward growth in the microcapsule host. Zn‐incorporated microcapsules are prepared via chemical etching of zeolitic imidazole framework‐8 polyhedra and are subsequently decorated with Ag by a galvanic displacement reaction between Ag+ and metallic Zn. Galvanically introduced Ag significantly reduces the energy barrier and increases the reaction rate for Li nucleation in the microcapsule host upon Li plating. Through combined electrochemical, microstructural, and computational studies, we verify the beneficial role of Ag‐assisted Li nucleation in facilitating inward growth inside the cavity of the microcapsule host and, in turn, enhancing electrochemical performance. This study provides new insights into the design of reversible host materials for practical Li metal batteries.

Tensile nanostructured hierarchically porous non-precious transition metal-based electrocatalyst for durable anion exchange membrane-based water electrolysis

Electrochemical water electrolysis is a promising method for sustainable hydrogen production while transiting towards hydrogen economy. Among many, the Anion Exchange Membrane (AEM) based water electrolyzer is an emerging yet potentially affordable technology on maturity for producing large-scale hydrogen accommodating the usage of Non-Platinum Group Metal (non-PGM) based inexpensive electrocatalysts. Herein, we demonstrate the excellent performance of a bifunctional Nickel Copper Phosphide-Nickel sulphide (NCP-NS) electrocatalyst with a unique tensile nanostructure obtained via a facile, controlled ambient galvanic displacement route. An AEM electrolyzer with a larger active area of 10 cm2 stacked with the symmetric NCP-NS electrodes and a membrane demonstrates scalability with a requirement of a mere 1.66 V to reach a current density of 10 mA cm−2. The nickel-copper phosphide boosts the kinetics of charge transfer between the electrode and electrolyte interface, while a unique combination of a few nickel sulphide phases present in the catalyst provides sufficiently appropriate active sites for the overall water electrolysis. For the first time, we report a room temperature performance of ∼ 230 mA cm−2 at 2 V for a non-PGM-based bifunctional electrocatalyst with exceptional durability for over 300 h of operation in an AEM water electrolyser with a retention rate of 95 %-97 % at a current density range of 80–800 mA cm−2.

Room temperature synthesis and hydrophobic surface protection of silver dendrites for hydrogel stretchable sensors

Hydrogel stretchable sensors have gained increasing popularity as essential components for next-generation flexible electronics. Stringent standards have been placed on the cost, conductivity, stability, and sensitivity of composites. In this work, highly conductive silver dendrites with uniform morphology were successfully synthesized by galvanic displacement reaction. Due to the more complex three-dimensional structure of the silver dendrites, the percolation threshold of the conductive composites was reduced to approximately 45 wt%. By decorating the as-prepared silver dendrites with a dense and hydrophobic dodecanethiol layer, the issue of hygrothermal stability in the hydrogel matrix has been successfully addressed. Silver dendrites conductive composites exhibited excellent electrical conductivity (8.57×10−4Ω∙cm for 65 wt% silver dendrites) and sensing properties. The stretchable conductors exhibited high sensitivity and linearity with F= 9.48 and R2= 0.9967. Therefore, human-computer interaction was successfully carried out by monitoring the movement of fingers, wrists, elbows, and knees of the human body.

Fabrication and characterization of hybrid thermoelectric materials based on aligned nanowires.

This study introduces the synthesis of a hybrid thermoelectric material with enhanced conductivity and a high Seebeck coefficient, leveraging the properties of Te nanowires (NWs) and the conductive polymer PEDOT:PSS. Te NWs were synthesized using the galvanic displacement reaction. To further enhance conductivity, Ag-Te NWs were synthesized under optimized conditions via the Ag topotactic reaction, achieving desired results within 7min using ethylene glycol and AgNO3. This hybrid material exhibited an electrical conductivity of 463S/cm, a Seebeck coefficient of 69.5μV/K at 300K, and a power factor of 260μW/mK2. These metrics surpassed those of conventional Te/PEDOT:PSS hybrids by a factor of 3.6, highlighting the superior performance of our approach. This study represents a significant advancement in thermoelectric materials, improving both conductivity and efficiency.

(Keynote) Iridium Deposition By Galvanic Displacement of Cu on a One-Pot Configuration

Water electrolysis with proton exchange membranes (PEMWE) is expected to play a vital role in the future hydrogen infrastructure. The hydrogen evolution is effectively catalyzed by platinum, and iridium oxide is a highly active and reasonably stable catalyst for the oxygen-evolution reation (OER) [1]. However, iridium is costly and scarce, and efficient utilization of it is necessary for large-scale deployment of PEMWE technology. This can be achieved in various ways, such as dilution with other and cheaper compounds such as Ta2O5 [2] and alloying with more abundant metals followed by post-synthesis-treatment such as de-alloying or surface enrichment [3]. A possible solution is the application of ultra-thin layers of iridium oxide on a less costly substrate. A suitable method for achieving such layers is that of surface-limited galvanic displacement [4], i.e. the underpotential deposition of a metal M followed by its oxidation by another and more noble metal N.In this work we have investigated Ir plating onto a polycrystalline gold electrode by successive galvanic displacement of Cu monolayers in a one-pot method, i.e by performing the Cu underpotential-deposition step in a solution also containing iridium precursors. The process is indicated in the figure. By using low concentrations of the precursors H2IrCl6 and IrCl3 in H2SO4, Cu submonolayers could be formed on a Au(poly) rotating disc electrode by underpotential deposition without any significant direct electrochemical formation of Ir or IrO2. The Cu submonolayer formed was then available for reaction with the Ir precursor before a new Cu submonolayer was formed. By evaluating the amount of Cu deposited in each submonolayer and the resulting Ir deposit, our results indicate that H2IrCl6 is reduced onto the Au electrode as metallic Ir via the formation of Ir(III). Due to transport of Ir(III) away from the reaction surface, this resulted in a low yield. No Ir deposited was achieved from IrCl3 solutions, possibly due to adsorption of irreducible species onto the Au surface.The results will be discussed in terms of possible reaction paths and the relative stability of iridium complexes in chloride-containing solutions. Acknowledgements This work was performed within the project "Metal(-oxide) catalyst-monolayer as cost-effective electrocatalysts for PEM water electrolysis" funded by the Research Council of Norway, contract no. 254976/E20. References Carmo, D. L. Fritz, J. Mergel, and D. Stolten, “A comprehensive review on PEM water electrolysis,” Int. J. Hydrogen Energy, 38, pp. 4901–4934, 2013.Comninellis and G. P. Vercesi, “Characterization of DSA®-type oxygen evolving electrodes: Choice of a coating,” J Appl Electrochem, 21, pp. 335–345, 1991.N. Nong, L. Gan, E. Willinger, D. Teschner, and P. Strasser, “IrOx core-shell nanocatalysts for cost- and energy-efficient electrochemical water splitting,” Chem. Sci., 5, pp. 2955–2963, 2014.Brankovic, J. X. Wang, and R. R. Adžic, “Metal monolayer deposition by replacement of metal adlayers on electrode surfaces,” Surface Science, vol. 474, L173–L179, 2001. Figure 1

Enhanced lithiophilicity via bismuth-infused framework for advanced lithium metal batteries

Utilizing carbon materials as 3D lithium (Li) hosts hold a significant interest in constructing high-energy batteries. However, there are ongoing challenges associated with these frameworks owing to their poor Li affinity. Recent advancements, including alloying reactions with precious metals like silver (Ag) and gold (Au), have emerged as a promising technique to enhance the electrochemical performance of these host materials. Nevertheless, the search for cost-effective alternatives remains a pressing demand. Herein, this work employed galvanic displacement (GD) to integrate bismuth into disordered porous carbon (Bi-DPC) and optimized across different concentrations (0.01, 0.05, 0.1 M). As a result, the Li deposition onto the Bi-DPC surface exhibited dendrite-free planar morphologies, revealing an outstanding electrochemical performance, including a high CE of around 100 % over more than 100 cycles. These findings underscore the potential of Bi-infused porous carbon as a promising alternative for enhancing Li deposition processes.

Galvanic Displacement Reaction Enabled Specific and Sensitive Detection of Bacteria with a Digital Photocorrosion GaAs/AlGaAs Biosensor.

The conjugation of ionic gold with bacterial antibodies makes it possible to induce a specific interaction between targeted bacteria and the surface of a GaAs/AlGaAs biochip. The process of immobilization is based on a galvanic displacement reaction (GDR) involving electron transfer between GaAs and Au3+ ions that leads to the formation of a Au-Ga alloy anchoring bacteria to the biochip surface. The GDR-based immobilization of Escherichia coli on biochips comprising a stack of GaAs/AlGaAs nanolayers (dGaAs = 12 nm, dAlGaAs = 10 nm) was confirmed by X-ray photoelectron spectroscopy and atomic force microscopy-based infrared experiments. We report the successful application of this approach for highly sensitive detection of E. coli with a digital photocorrosion (DIP) biosensor. The photoluminescence (PL) monitored DIP of GaAs/AlGaAs nanolayers results in the formation of a PL intensity maximum whose temporal appearance depends on the electric charge transfer between bacteria and the biochip. The formation of a robust bacteria-biochip interface achieved with the GDR process allowed us to observe the role of bacteria on the temporal position of a PL intensity maximum related to the etching of two pairs of GaAs/AlGaAs nanolayers extending up to 24 nm below the biochip surface. We demonstrate the attractive detection of E. coli at 250 CFU/mL, and we discuss the potential of this approach for designing a family of biosensors addressing the quasi-continuous monitoring of a water environment for the presence of pathogenic bacteria.

Synthesis of bimetallic-nanocrystal-decorated rice bowl-shaped polymer particles for catalytic Cr(VI) remediation

Rice-bowl shaped polymer particles with convex and concave surfaces have emerged as promising noble metal catalyst supports. However, their synthesis and integration with catalytic materials using environmentally friendly methods have remained a challenge. This study presents a sustainable and efficient approach for synthesizing rice-bowl-shaped polystyrene (PS) particles and explores their potential as catalyst supports. The key to achieving this morphology lies in the utilization of anisotropic PS seeds, specifically hollow dimpled PS seeds. Uniform rice-bowl-shaped PS particles are obtained by dispersing these seeds in an oil-in-water (O/W) emulsion and allowing them to dry under ambient conditions. Non-toxic reducing agents and environmentally friendly solvents are employed for the in-situ chemical reduction process and galvanic displacement reaction to synthesize bimetallic (Ag/Pd) nanocrystals on the surfaces of the PS particles. The resulting Ag/Pd-coated PS particles exhibit excellent catalytic activity as microreactors for Cr(VI) reduction in water, while demonstrating remarkable stability during repeated use without significant loss of activity. Furthermore, the shape of the rice-bowl particles facilitates efficient packing and stacking, leading to enhanced catalytic performance not only in bulk solutions but also in confined spaces. This study highlights the potential of rice-bowl-shaped polymer particles as efficient and environmentally friendly catalyst supports, paving the way for the development of green catalytic applications.

Functionalized Copper Nanoparticles with Gold Nanoclusters: Part I. Highly Selective Electrosynthesis of Hydrogen Peroxide.

Copper nanoparticles (CuNPs) and gold nanoclusters (AuNCs) show a high catalytic performance in generating hydrogen peroxide (H2O2), a property that can be exploited to kill disease-causing microbes and to carry carbon-free energy. Some combinations of NPs/NCs can generate synergistic effects to produce stronger antiseptics, such as H2O2 or other reactive oxygen species (ROS). Herein, we demonstrate a novel facile AuNC surface decoration method on the surfaces of CuNPs using galvanic displacement. The Cu-Au bimetallic NPs presented a high selective production of H2O2 via a two-electron (2e-) oxygen reduction reaction (ORR). Their physicochemical analyses were conducted by scanning electron microscopy (SEM), transmitting electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). With the optimized Cu-Au1.5NPs showing their particle sizes averaged in 53.8 nm, their electrochemical analysis indicated that the pristine AuNC structure exhibited the highest 2e- selectivity in ORR, the CuNPs presented the weakest 2e- selectivity, and the optimized Cu-Au1.5NPs exhibited a high 2e- selectivity of 95% for H2O2 production, along with excellent catalytic activity and durability. The optimized Cu-Au1.5NPs demonstrated a novel pathway to balance the cost and catalytic performance through the appropriate combination of metal NPs/NCs.

Cu@PtRu Core–Shell Nanostructured Electrocatalysts Anchored on Reduced Graphene Oxide toward Methanol Oxidation

This work reports the influence of a reduced graphene oxide (rGO) support on the catalytic performance of Cu@PtRu/rGO electrocatalysts toward methanol oxidation in an acidic medium. These electrocatalysts are synthesized via a two-step reduction method; the first step utilizes ethylene glycol for the reduction of Cu2+ ions, forming Cu/rGO. In the second step, spontaneous redox reactions take place, in a process known as galvanic displacement, where the Pt2+ and Ru3+ species are reduced to form PtRu layers, and the copper is partially oxidized to the solution. Then, the Cu@PtRu/rGO core–shell is produced, comprising Cu in the inner structure (core) and PtRu on the outer part (shell). To compare the catalytic performance of the prepared nanocatalysts (NCs), Pt/C, PtRu/C, and Cu@PtRu/C are also synthesized on Vulcan XC-72R carbon. All catalysts are characterized via X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Cyclic voltammetry (CV) and chronoamperometry (CA) are employed to measure the electrochemical performance. The core–shell/rGO combination is superior in catalytic activity to the traditional Pt/C, PtRu/C, and Cu@PtRu/C catalysts for the methanol oxidation reaction. These results suggest that Cu@PtRu/rGO exhibits a high bulk activity for methanol electrooxidation, a high stability, and a high tolerance to CO poisoning, meaning it is possible to reduce the platinum loading in proton-exchange membrane fuel cells (PEMFCs).

Spatial Confinement of Li Metal in Hollow Microcapsule Hosts Enabled by Heteroatom-Driven Inward Growth

In recent years, the demand for advanced batteries with high energy densities has increased significantly, along with the growing demand for electric vehicles. Li metal has garnered considerable research attention as a promising anode material because of its high theoretical specific capacity (3860 mAh g−1) and low electrochemical equilibrium potential (−3.040 V vs. standard hydrogen electrode). However, Li metal batteries still have several hurdles in their practical application because Li metal anodes experience infinite volume expansion, which induces continuous rupture and formation of solid-electrolyte interphase (SEI) layers. This leads to electrolyte consumption and corrosion of Li metal, resulting in a low Coulombic efficiency and poor cycling performance. In addition, the uncontrollable dendrite growth of Li metal may cause early battery failure and safety issues. To address these problems, extensive research efforts have been made, including artificial SEI layers, optimized electrolyte formula, and rational design of three-dimensional (3D) host materials.Among the various 3D host materials under development, carbon-based materials with hollow structures have been investigated extensively because of their attractive features. The enlarged void space (cavity) of the hollow hosts can accommodate a significant amount of Li deposits, while inhibiting volume changes during plating–stripping cycles. In addition, hollow carbon possesses much lower density than metal-based materials, thereby increasing the specific capacity and energy density. However, the lithiophobic nature of carbon combined with its high resistance to Li+ transport through nanopores on the walls significantly hinders the formation of Li deposits inside the cavity. Li may nucleate on the outer surface of the carbon particles in a nonuniform manner, thereby causing the growth of Li dendrites and electrochemically inactive Li deposits.In this study, we synthesize metal-organic framework-derived carbon microcapsules with heteroatom clusters (Zn and Ag) on the capsule walls and demonstrate that Ag-assisted nucleation of Li metal alters the outward-to-inward growth in the microcapsule host. The cavity inside the microcapsule host, which was generated by etching with tannic acid, provides large void spaces for Li metal storage. Atomic Ag clusters decorated by a galvanic displacement reaction serve as preferential nucleation sites with a reduced energy barrier and promote the inward growth of Li metal in the cavity, while suppressing nonuniform Li plating on the outer surface. Through combined electrochemical, microstructural, and simulation studies, we verify the beneficial role of Ag-assisted Li nucleation in facilitating inward growth inside the cavity of the microcapsule host, resulting in enhanced electrochemical performance. This study provides new insights into the design of reversible host materials for practical Li-metal batteries.