Galvanic Replacement Reaction Research Articles

Arsenic (III) and (V) complexes from solvent free condition and their kinetic factors leading to arsenic nanoparticles

A clear melt from catechol and sodium salts of arsenic (III and V) were obtained individually from the grinding mixing protocol (GMP). The as-obtained molten mass from exothermic reaction between catechol and arsenic salts motivated isothermal titration calorimetry (ITC) advocating the propensity of complex catecholate formation. Individual ITC results substantiated structurally two different mono-anionic complexes, one for arsenic (III) and the other for arsenic (V) ions, of catechol in water at room temperature. Then, the compositions of both the mono-anionic complexes with stoichiometry 1:2 and 1:3 (w∕w) were confirmed for arsenic (III) and (V), respectively. It was shown here for the 1st time that both the complexes supplemented two neat precursors for useful arsenic nanoparticle (As NP) preparation from pH control redox reactions. Again, galvanic replacement reaction (GRR) between As NP and HAuCl4 evolved Au NPs of comparable size as that of As NPs. Thus, thermodynamic results, binding constant (Kb) values, redox kinetic studies and ion associate formation of the two catecholates clearly differentiated the stability (labile and inert character) of As(III) and As(V) catecholates. Conclusively, electrochemistry, galvanic replacement reaction, DLS, thermal analysis, and diverse spectrometric results provided 1st hand support for the complex catecholates of arsenic, a p-block metalloid as labile and inert characters respectively in two different (III) and (V) oxidation states.

Diffusive ex situ galvanic growth of metal nanocrystals on transmission electron microscopy grid

The uniform modification of commercial and standardized objects features considerable potential, as in the case of dip-pen lithography, biosensor kits, and disposable electrodes. In this study, we devised a dense nanoparticle array formation using the metallic mesh of a transmission electron microscopy (TEM) grid, which was formerly solely employed as a sampling stage. Incompletely oxidized cationic species generated from the galvanic replacement reaction of the metallic support mesh at the opposite side of the carbon layer diffused to the exposed top side and led to ex situ nanostar formation. A uniform nanoparticle array was obtained by immersion in an aqueous solution of replacing metal cations without reducing agents or surface energy-controlling compounds. Moreover, the array density was exclusively regulated by the incubation time. The straightforward nanoparticle array formation was successfully extended to various metal mesh TEM grids and different transition metal cations capable of spontaneous redox reactions. Cu mesh TEM grid and Mo grids could be utilized as sacrificial templates, and the growth of Au, Pd, Pt, Ag, and Rh nanostructures was confirmed.

Replacing the Gallium Oxide Shell with Conductive Ag: Toward a Printable and Recyclable Composite for Highly Stretchable Electronics, Electromagnetic Shielding, and Thermal Interfaces.

Liquid metal (LM)-based composites hold promise for soft electronics due to their high conductivity and fluidic nature. However, the presence of α-Ga2O3 and GaOOH layers around LM droplets impairs conductivity and performance. We tackle this issue by replacing the oxide layer with conductive silver (Ag) using an ultrasonic-assisted galvanic replacement reaction. The Ag-coated nanoparticles form aggregated, porous microparticles that are mixed with styrene-isoprene-styrene (SIS) polymers, resulting in a digitally printable composite with superior electrical conductivity and electromechanical properties compared to conventional fillers. Adding more LM enhances these properties further. The composite achieves EMI shielding effectiveness (SE) exceeding 75 dB in the X-band frequency range, even at 200% strain, meeting stringent military and medical standards. It is applicable in wireless communications and Bluetooth signal blocking and as a thermal interface material (TIM). Additionally, we highlight its recyclability using a biodegradable solvent, underscoring its eco-friendly potential. This composite represents a significant advancement in stretchable electronics and EMI shielding, with implications for wearable and bioelectronic applications.

In Vitro Assessment of Gallium Nanoalloy Hydrogels for Antimicrobial and Wound Healing Applications.

Chronic and recurring wounds pose a significant challenge in modern healthcare, leading to substantial morbidity. These wounds allow pathogens to colonize, potentially resulting in local and systemic infections. Current interventions need to be revised and become increasingly less reliable due to the emergence of antibiotic resistance. In the present study, we aim to address these issues by fabricating hydrogels impregnated with gallium-based nanoalloys for their antimicrobial activity. Gallium liquid metal nanoparticles (approximately 100 nm in diameter) were alloyed in different combinations with bismuth and silver ions through a galvanic replacement reaction. These multimetallic hydrogels showed favorable antibacterial activity against the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa, as observed with fluorescence microscopy and inhibition assays. The multimetallic hydrogels showed no toxicity against murine macrophages or human dermal fibroblasts and enhanced in vitro wound healing. The development of these innovative gallium-based hydrogels represents a promising strategy to combat chronic wounds and their associated complications, offering an effective alternative to current antimicrobial treatments amidst rising antibiotic resistance.

Strain-Controlled Galvanic Synthesis of Platinum Icosahedral Nanoframes and Their Enhanced Catalytic Activity toward Oxygen Reduction.

The unique strain distribution on the surface of a Pd icosahedral nanocrystal is leveraged to control the sites for oxidation and reduction involved in the galvanic replacement reaction. Specifically, Pd is oxidized and dissolved from the center of each {111} facet due to its tensile strain, while the Pt(II) precursor adsorbs onto the vertices and edges featuring a compressive strain, followed by surface reduction and conformal deposition of the Pt atoms. Once the galvanic reaction is initiated, the {111} facets become more vulnerable to oxidation and dissolution, as the vertices and edges are protected by the deposited Pt atoms. The site-selected galvanic reaction naturally results in the formation of Pt icosahedral nanoframes covered by compressively strained {111} facets, which show enhanced catalytic activity and durability toward oxygen reduction relative to commercial Pt/C.

Plasmonic Nanocubes with a Controllable "Crescent Arc" Facet: Tunable Hotspot Engineering for Highly Reliable and Sensitive SERS Detection.

The fine control of the nanogap and morphology of metal nanoparticles (NPs) has always been an obstacle, hindering the development and application of surface-enhanced Raman scattering (SERS) quantitative detection. Here, Au/4-mercaptobenzoic acid@Ag@Au-Ag bimetal core-shell nanocubes (NCs) with a "crescent arc" facet (C-Au/4MBA@Ag NCs) as a highly reliable and sensitive surface-enhanced Raman scattering SERS substrate is proposed for the first time. The bifunctional internal standard (IS) molecules (4MBA) govern the morphology of metal shells to maintain cubic configuration and provide calibration for SERS signals' flotation. In parallel, the controllable curvature of the C-Au/4MBA@Ag NCs is directly modulated by adjusting the relative rates of the galvanic replacement and co-reduction reaction, which generates a controllable interparticle nanogap to offer large depositing spaces for analytes and improve authoritative SERS signals' enhancement. The proposed C-Au/4MBA@Ag NCs exhibit an enhancement factor of up to 4.8 × 1010 and contribute to the ultralow RSD (7.9%). These C-Au/4MBA@Ag NCs also enable the detection of hazardous pesticide residues such as methamidophos and thiram in herbal plants with a complex matrix, with an average detection accuracy of up to 96%. In summary, this study achieves a fine control strategy of the "crescent arc" surface for improving SERS performance and explores the practical application potential for accurate and sensitive Raman detection of hazardous substances.

Chiral Symmetry Breaking in Colloidal Metal Nanoparticle Solutions by Circularly Polarized Light.

Shape symmetry breaking in the formation of inorganic nanostructures is of significant current interest. It was typically achieved through the growth of colloidal nanoparticles with adsorbed chiral molecules. Photochemical processes induced through asymmetric plasmon excitation by circularly polarized light in surface immobilized nanostructures also led to symmetry breaking. Here, we show that chiral symmetry breaking can be achieved by randomly rotating gold@silver core-shell nanobars in colloidal solution using circularly polarized illumination, where orientational averaging does not eliminate the symmetry breaking of an asymmetric plasmon-induced galvanic replacement reaction. Different morphological effects that are produced by circularly vs linearly polarized light illumination demonstrate the intricate effect of light polarization on the localized plasmonic-induced photochemical response. The essential features of this symmetry breaking, such as illumination wavelength dependence, were reproduced by simulations of circularly polarized light-excited-plasmon-induced hot-electron generation as the source for asymmetric metal deposition. The symmetry breaking becomes smaller in more symmetric geometrical shapes, such as triangular nanoprisms and nanocubes, and down to zero in spherical ones. The degree of symmetry breaking rises when the nanobars are immobilized on a substrate and illuminated from a single direction.

Improving Catalytic Performance via the Synergy of Tensile Lattice Strain and Plasmonic Enhancement in Defective AuPd@Pd Short Nanowires.

The synthesis of bimetallic nanocatalysts with strained crystal lattices has attracted considerable interest. This is because, beyond the electronic structure modifications realized through elemental doping, the strain effect offers an extra mechanism to fine-tune the electronic structures, thereby possibly improving the catalytic performances. We present a method for constructing defective AuPd@Pd short nanowires, achieved through a controlled galvanic replacement reaction between short AuCu nanowires and Pd precursors. Advanced structural analyses using spherical aberration-corrected transmission electron microscopy (AC-TEM) validated the expanded crystal lattice on the nanowire surface and also demonstrated pronounced plasmonic absorption in the UV-vis region. Leveraging both plasmonic absorption and strain effects, the AuPd@Pd short nanowires displayed a higher apparent rate constant compared to Pd nanoparticles. Integrating molecular dynamic simulations with density functional theory calculations revealed that the tensile strain on AuPd@Pd short nanowires benefited the catalytic activity by elevating the d-band center, thereby intensifying the adsorption of p-nitrophenol. The current research introduces a unique method for synthesizing noble metal nanocrystals with specific dimensions and elucidates the rational development of high-performance plasmonic nanocatalysts through synergistic exploitation of the beneficial strain effect.

Plasmon-induced efficient solar-driven H2 production using bimetallic core-shell Cu@Ag:TiO2 nanocomposite photocatalyst

The nano-interface formed by bimetallic Cu@Ag nanoparticles (NPs) on a TiO2 surface enhances charge separation through plasmonic heterojunctions. These bimetallic Cu@Ag NPs were synthesized via the a galvanic replacement reaction (GRR) involving Ag+ in an aqueous medium and metallic Cu NPs on TiO2. During the GRR, Cuδ+ and Agδ+ charge pairs are generated by electron transfer from the catalyst surface. These charge pairs act as active sites, significantly enhancing photocatalytic hydrogen production. Additionally, the cubic crystalline phase of metallic Cu NPs is maintained after the GRR process with Ag ions, while the size of bimetallic Cu@Ag NPs remains constant. Consequently, Cu@Ag NPs supported on TiO2 (Cu@Ag:TiO2) exhibit increased donor charge density of 1.66 × 1020 cm−3 and facilitate rapid charge transfer. As a result, the photocatalytic hydrogen production rate of Cu@Ag:TiO2 is 20 times higher than that of pristine TiO2. Moreover, the visible-light responsive photocatalytic activity of Cu@Ag:TiO2 NPs reaches 3.4 mmol g−1 over 5 hours, which is 78 times higher than that of pristine TiO2. This remarkable enhancement is attributed to the formation of a plasmonic heterojunction with close contact between Cu@Ag and TiO2, enabling efficient charge carrier separation.

Bismuth nanosheets guided zinc deposition enabled long-life aqueous zinc-based flow batteries

The poor cycling durability and low Coulombic efficiency (CE) of zinc (Zn) anodes substantially restrict their further development, which should be attributed to the severe uneven plating and hydrogen evolution reaction (HER) across the repeated plating/stripping processes. Herein, bismuth nanosheets decorated graphite felt (BiNS/GF) is constructed for Zn anode via galvanic replacement reaction. BiNS/GF affords more robust Zn nucleation sites, lower Zn nucleation overpotential and higher HER overpotential to guide even and dense Zn deposition. In addition, a total internal reflection imaging method is employed to detect micro-bubbles generated by HER on the electrode surface, revealing that BiNS prevents the formation of micro-bubbles and thus avoids dead Zn caused by unstable Zn deposition. As a proof of concept, BiNS/GF exhibits an average CE of 99.2 % in 300 cycles and a peak power density of 295.2 mW cm−2 at a current density of 380 mA cm−2 in aqueous neutral zinc-iron flow batteries. Therefore, it is reasonably anticipated that the BiNS/GF may emerge as suitable electrode for other aqueous zinc-based flow batteries.

A Liquid Metal-Based Temperature-Responsive Low-Toxic Smart Coating for Anti-Biofouling Applications in Marine Engineering.

Titanium alloys have been widely used in marine engineering fields. However, because of high biocompatibility, they are vulnerable to biofouling. In this work, based on the micro-arc oxidation technology and spontaneous galvanic replacement reaction, a temperature-responsive low-toxic smart coating consisting of liquid metal particles is designed to control the release of Ga3+, Cu2+, and Cu1+ ions in different temperatures. This technology can ensure the full release of active ingredients within the target temperature range, intelligently maintaining the excellent anti-biofouling performance, while saving active ingredients. After being immersed in culture media with Sulfate-Reducing Bacteria (SRB) for 14 days at 10, 20, and 30°C, at the optimal activity temperature of 30°C for SRB, the best sample releases the highest amounts of Ga3+, Cu2+, and Cu1+ ions, demonstrating a 99.9% bactericidal rate. When the temperature decreases to 10°C, the activity level of SRB is very low, and the smart coating can also reduce the released ions correspondingly, still with a 97.3% bactericidal rate. The remarkable anti-biofouling performance is attributed to the physical damage and lethal ions interaction. Furthermore, the best sample exhibits good corrosion resistance. This work presents a design route for smart anti-biofouling coatings for temperature-responsive.

Rational design of stable Cu and AuCu nanoparticles for investigations of size-enhanced SERS applications

BackgroundWhile significant progress has been made to clarify the effects of Au and Ag nanoparticle size on SERS enhancement, research on the size effects of copper nanoparticles and copper-related nanoalloys on SERS enhancement remain scarce. Nanoscale copper (Cu) is important because of its unique sensing and catalytic properties; however, research on its size and compositional effects remains a significant challenge because of the intricate fabrication process and difficulty in preventing oxidation. ResultsOur study elucidated the size-dependent, surface-enhanced Raman scattering (SERS) of Cu NPs, particularly the sensing capabilities of both electromagnetic (EM) SERS at 1.5 × 103 and chemical enhancement (CE) SERS at 3.6 × 104 of approximately 58 nm Cu NPs. Additionally, a solution aging examination revealed preservation of the metal-related core structure, surface plasmon resonance, and SERS features of the PSMA/ONPG-coated Cu NPs for up to 7 days. With the introduction of galvanic replacement reactions and laser ablation syntheses, the incorporation of Au atoms enabled the fabrication of 7–75 nm AuxCuy nanoparticles by using the remaining Cu core after aging in water, which offered precise control over the Cu/Au ratio from 5/95 to 29/71. SERS measurements of the large AuxCuy nanoparticles amplified up to 1.4 × 104 of the EM-mediated vibrational signals from the adsorbed molecules. The strong Au–S chemical bonds of the Au-rich AuxCuy nanocrystals increased the CE SERS to 5.5 × 104, whereas the Au3Cu1 crystals at the AuxCuy interface decreased the CE SERS but improved the electron transfer for catalysis via SERS detection. SignificanceOur research provides further insight into the structural and size effects of Cu and AuCu alloys used as SERS enhancers and offers avenues for designing cutting-edge SERS catalytic sensors tailored to Cu-related catalytic reactive structures.For the first time, we also manipulated the Cu atomic structure and surface composition to understand the significance of surface effects on SERS substrates of the Cu series from a nanoscale analytical perspective.

Silver-based bimetallic nanozyme fabrics with peroxidase-mimic activity for urinary glucose detection

The enhanced catalytic properties of bimetallic nanoparticles have been extensively investigated. In this study, bimetallic Ag-M (M = Au, Pt, or Pd) cotton fabrics were fabricated using a combination of electroless deposition and galvanic replacement reactions, and improvement in their peroxidase-mimicking catalytic activity compared to that of the parent Ag fabric was studied. The Ag-Pt bimetallic nanozyme fabric, which showed the highest catalytic activity and ability to simultaneously generate hydroxyl (•OH) and superoxide (O2•−) radicals, was assessed as a urine glucose sensor. This nanozyme fabric sensor could directly detect urinary glucose in the pathophysiologically relevant high millimolar range without requiring sample predilution. The sensor could achieve performance on par with that of the current clinical gold standard assay. These features of the Ag-Pt nanozyme sensor, particularly its ability to avoid interference effects from complex urinary matrices, position it as a viable candidate for point-of-care urinary glucose monitoring.Graphical

(Invited) Synthesis and Visible-Plasmonic Properties of Intermetallic Nanoparticles

The past research on inorganic nanomaterials that exhibit intrinsic localized surface plasmon resonance (LSPR) in the visible region has focused on well-disperse nanoparticles (NPs) including group 11 elements (Au, Ag, and Cu) [1]. Recent theoretical studies on photo-excited electron dynamics in Au NPs have revealed that not only the interband transition but also the screening caused by the vibrations of bound electrons by visible light are important for visible LSPR [2]. However, the correlation between the electronic and crystal structure (as a means of controlling the screening effect) remains unclear because most alloys based on group 11 elements have a face-centered cubic (fcc)-based structure. Here, we show that well-disperse spherical intermetallic Pd-based alloy NPs and Pt-based alloy NPs with non-close packed structure intrinsically exhibit LSPR absorption in the visible region.It is well known that chemical conversion of inorganic NPs via element substitution reactions, such as ion exchange reactions [3] and galvanic replacement reactions, can overcome the difficulties associated with controlling the size, shape, chemical composition, and crystal structure in conventional syntheses [4-6]. Especially, alloying enables us to drastically modulate the electronic properties of metallic NPs. The retained shape of the parent-NPs in element replacement reactions provides an opportunity to obtain non-equilibrium unique structures and even new structures of inorganic NPs. We demonstrate that various Pd-based alloy NPs with a B2 structure were synthesized by the element replacement reactions with Pd–P NPs and showed LSPR in the visible region [7]. On the other hand, we successfully synthesized pseudospherical PtIn2 intermetallic NPs with a C1 structure as uncommon types of visible plasmonic NPs [8].Consequently, we can extract the design principles of intermetallic NPs that exhibit LSPR in the visible region in terms of the crystal and electronic structures as follows. (i) The electronic structure of intermetallic NPs should be similar to that of group 11 element NPs, that is, the sp-band crossing the Fermi level and d-band edge of noble metal like Pt around the visible region. The deeper d-band edge of another base metal like indium less affects the red-shift of LSPR wavelength. (ii) The intermetallic NPs should have non-close packed structure to cause strong screening effect by a small number of d-electrons of noble metal. The intermetallic NPs, which satisfy the above two requirements, are expected to show LSPR in the visible region and serve as novel plasmonic photocatalysts [9].[1] Kawawaki, T.; Teranishi, T. et al., J. Am. Chem. Soc. 2019, 141, 8402–8406.[2] Iida, K.; Noda, M.; Ishihara, K.; Nobusada, K. J. Phys. Chem. A 2014, 118, 11317–11322.[3] Saruyama, M.; Sato, R.; Teranishi, T. Acc. Chem. Res. 2021, 54, 765–775.[4] Wu, H.-L.; Sato, R.; Teranishi, T. et al., Science 2016, 351, 1306–1310.[5] Li, Z.; Saruyama, M.; Asaka, T.; Tatetsu, Y.; Teranishi, T. Science 2021, 373, 332–337.[6] Matsumoto, K.; Sato, R.; Tatetsu, Y.; Teranishi, T. et al., Nat. Commun. 2022, 13, 1047.[7] Sato, R.; Takekuma, H.; Teranishi T. et al., to be submitted.[8] Takekuma, H.; Sato, R.; Iida, K.; Teranishi, T. et al., Adv. Sci., in revision.[9] Lian, Z; Teranishi, T. et al., J. Am. Chem. Soc. 2019, 141, 2446–2450.

Insights into the Structure and Activity of Bimetallic Au/Cu2O Catalysts during CO2 Electroreduction to C2 products

Despite its promising performance for C2+ product formation in electrochemical reduction of CO2 (CO2RR), Cu-based catalysts exhibit a relatively poor selectivity towards important chemical intermediates such as ethylene and ethanol. Up to 16 different products can typically be formed during CO2RR.1 Cu is the only element that can form C-C bonds at an appreciable rate.2 Therefore, it is critical to better understand the active sites of Cu-based electrocatalysts, as it can lead to better catalyst design with improved selectivity towards desired products. A common approach is to investigate the reactivity of well-defined surface terminations of Cu, which can be achieved by employing shape-controlled (nano)particles.3 Here, we expanded on such studies by evaluating the impact of Au on well-defined Cu2O surfaces for the electrochemical reduction of CO2. This promoter metal was chosen, because it can reduce CO2 to CO, which is widely accepted as the key intermediate for C-C coupling.2,4 In this study, 40 nm Cu2O nanocubes that predominantly expose the (100) facet were synthesized with a ligand-free method. The (100) facet is more active in the production of ethylene at the expense of unwanted methane formation, which takes place predominantly at the (111) facet.3 The surface of the nanocubes was decorated with Au nanoparticles by a galvanic replacement reaction. HAADF-STEM images of the catalysts with various Au loadings are shown in Figure 1a-d. After addition of Au nanoparticles, the shape of the Cu2O nanocubes was preserved. However, the Au nanoparticles were highly dispersed at low loadings (1 mol % Au) whereas Au clusters were observed at higher loadings (10 mol % Au). This result was in line with synchrotron X-ray diffraction (XRD) results, whereby the Au(111) reflection appears for the 10Au/Cu2O sample. Besides, the formation of a Au-Cu alloy and CuO phase was confirmed as well. The highly dispersed nature of the Au nanoparticles at low loadings was further established by Au 4f X-ray photoelectron spectroscopy (XPS), whereby a shift towards higher binding energies was observed as compared to the samples with higher Au loadings. The electrocatalytic performance of the catalysts was assessed over a range of potentials in neutral electrolyte (0.1 M KHCO3) in H-cell configuration. With highly dispersed Au as promotor, we found that the formation of ethylene and ethanol was significantly enhanced (Figure 1e-f). More specifically, the Faradaic effiency towards ethanol increased by roughly 1.5 times by introducing 1 mol % Au to the Cu2O nanocubes. Surprisingly, the 10Au/Cu2O sample displayed the lowest Faradaic efficiency for C2 products. We believe that the dispersion of Au on the Cu2O surface plays an important role in the product formation, whereby CO can be formed at Au sites and diffuse to Cu sites in proximity for further reduction to C2 products (CO spillover). To further study structure-activity relationships, we performed in-situ X-ray absorption spectroscopy (XAS) measurements. Figure 1g shows the normalized Cu K-edge X-ray absorption near-edge structure (XANES) of the Cu2O and Au/Cu2O samples in the final state. The evolution of the Cu(0), Cu(I) and Cu(II) fractions was followed by Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) analysis. This analysis revealed that the final oxidation state of the catalysts is different. The Cu(I)/Cu(0) ratio shows the following trend 1Au/Cu2O > 5Au/Cu2O > Cu2O > 10Au/Cu2O. Based on these observations, we hypothesize that the oxidation state of Cu affects the product distribution and in particular, the formation of oxygenates. The presence of Cu(I) species and the formation of Cu(0) species during CO2 electroreduction was further confirmed with in-situ XRD measurements. Finally, we performed quasi in-situ XPS measurements to study the reduction of the surface of the catalysts. Acknowledgements This publication is part of the research programme 'Reversible Large-scale Energy Storage' (RELEASE) with project number 17621 which is financed by the Dutch Research Council (NWO).

Hydrogen Evolution Atomic Cluster Catalysts-Decorated Hierarchical Nanoporous Zinc for on-Demand Hydrogen Generation By Metal Hydrolysis

In recent years, there has been an increasing interest in nanoporous metals due to their wide range of applications, including catalysis, electrocatalysis, energy storage, actuation, and plasmonics. However, considerable attention has been given to precious nanoporous metals such as nanoporous Au, Pd, Pt, Ag, and Cu due to their low chemical reactivity, which makes them relatively easy to synthesize and characterize. Less precious nanoporous metals such as nanoporous Zn, Al, and Mg have been rarely fabricated and characterized because of their relatively high chemical reactivity 1. In this talk, I will present a novel, highly scalable approach to making hierarchical nanoporous zinc (NP-Zn) decorated with atomic clusters of hydrogen evolution catalysts for on-demand hydrogen generation by metal hydrolysis. Our approach involves selective etching in combination with galvanic replacement reactions. The conventional selective etching method requires several days to create a monolithic piece of NP-Zn 2. Our approach creates the same amount of hierarchical NP-Zn in less than 5 minutes, instead of several days. In our work, we used focused ion beam/scanning electron microscopy techniques to reveal the internal nanoscale morphology of the hierarchical NP-Zn, and small-angle X-ray scattering to analyze the pore size distribution. In general, when NP-Zn is used for hydrogen generation by metal hydrolysis, the hydrogen generation yield is low, typically around 20%. This is because zinc is naturally a poor hydrogen evolution material. Our process overcomes this issue by creating NP-Zn with its interface decorated with clusters of hydrogen evolution catalysts, which enables hydrogen generation yield exceeding 90% depending on the catalyst loading. References (1) Fu, J.; Welborn, S. S.; Detsi, E. Dealloyed Air- and Water-Sensitive Nanoporous Metals and Metalloids for Emerging Energy Applications. ACS Appl. Energy Mater. 2022, 5 (6), 6516–6544. https://doi.org/10.1021/acsaem.2c00405.(2) Fu, J.; Deng, Z.; Lee, T.; Corsi, J. S.; Wang, Z.; Zhang, D.; Detsi, E. pH-Controlled Dealloying Route to Hierarchical Bulk Nanoporous Zn Derived from Metastable Alloy for Hydrogen Generation by Hydrolysis of Zn in Neutral Water. ACS Appl. Energy Mater. 2018, 1 (7), 3198–3205. https://doi.org/10.1021/acsaem.8b00419.

Monitoring the Dynamics of the Galvanic Replacement Reaction to Develop Free-Standing Electrocatalysts

Hydrogen (H2) is well-known for its potential to become the future fuel and bring a more sustainable energy system [1]. The selective electrooxidation of organic compounds from biomass appears to be a possible substitute for the kinetically slow oxygen evolution reaction (OER) at the anode, which increases the electrical energy input for a conventional water electrolysis in alkaline media [2]. However, this approach is currently impeded by limited fundamental knowledge of the different active sites of electrocatalysts. The latter can be used to control selectivity at low potential and high current density to co-generate value-added products at the anode instead of CO2 by complete oxidation. Nanostructured gold-based multi-metal electrocatalysts can meet such objectives. Particularly in the electro-valorization of cellulosic biomass at electrode potentials unfavorable to C-C bond breaking and high overall cell voltage.To develop such electrocatalysts, we have initiated a multivariate methodology to study the dynamics of galvanic replacement between silver and gold. This procedure allows us to control nanoporosity and nanoalloying in the resulting gas diffusion electrode (GDE): GDE-Ag1-xAux. GDE-Ag represents the electrode upon which Ag particles were electrochemically grown prior to reaction with Au(III). Thermodynamically, silver with E°(Ag+/Ag) = 0.8 V vs SHE (standard hydrogen electrode) can be replaced by gold with E°(AuCl4 –/Au) = 1.0 V vs SHE according to: 3Ag + xKAuCl4(aq) → 3xAgCl + xKCl + Ag3-3xAux.[2,3] From a kinetic point of view, the challenge is to capture in real time the formation of metal cages of Ag-Au alloys after a '3by1' atomic exchange that introduces nanoporosity and electronic strain as silver and gold have a similar atomic radius. To interrogate the driving force behind this redox process, we have also established an electrochemical methodology to extract quantitative data, allowing detailed capture of the mixed electrochemical and mass transport (diffusion) kinetics. As the precipitation product AgCl leads to pore fouling, we have developed an efficient methodology to trigger its instant dissolution as soon as it is formed, thus promoting the production of a high-quality alloy. As shown in Figure 1, upon injection of a KAuCl4 solution into a degassed solution in contact with the GDE-Ag electrode, the open circuit potential (OCP) begins to change. This evolution is due to the modification of the electrochemical interface as silver atoms are progressively replaced by gold atoms. Thereby, leading to a regulated potential defined either by the Ag(I)/Ag redox couple, or by the Au(III)/Au pair. Interestingly, we found that the OCP variation logically depends on initial conditions such as Ag loading on the GDE, KAuCl4 concentration, Ag particle size, etc. This fundamental knowledge has led to the synthesis of efficient electrocatalysts for the oxidation of cellulose subunits in alkaline media with an onset electrode potential much lower than OER (E < 1 V vs RHE (reversible hydrogen electrode)). Indeed, the formation of an alloy phase, the creation of nanoporosity within it and the free-standing nature amplify, through synergistic and electronic effects, the electrocatalytic efficiency. Acknowledgments This work was funded by French National Research Agency (ANR-22-CE43-0004).

Direct Electroplating Ruthenium Precursor on the Surface Oxidized Nickel Foam for Efficient and Stable Bifunctional Alkaline Water Electrolysis.

Water electrolysis to produce hydrogen (H2) using renewable energy is one of the most promising candidates for realizing carbon neutrality, but its reaction kinetics is hindered by sluggish anodic oxygen evolution reaction (OER). Ruthenium (Ru) in its high-valence state (oxide) provides one of the most active OER sites and is less costly, but thermodynamically unstable. The strong interaction between Ru nanoparticles (NPs) and nickel hydroxide (Ni(OH)2) is leveraged to directly form Ru-Ni(OH)2 on the surface of a porous nickel foam (NF) electrode via spontaneous galvanic replacement reaction. The formation of Ru─O─Ni bonds at the interface of the Ru NPs and Ni(OH)2 (Ru-Ni(OH)2) on the surface oxidized NF significantly enhance stability of the Ru-Ni(OH)2/NF electrode. In addition to OER, the catalyst is active enough for the hydrogen evolution reaction (HER). As a result, it is able to deliver overpotentials of 228 and 15mV to reach 10mA cm-2 for OER and HER, respectively. An industry-scale evaluation using Ru-Ni(OH)2/NF as both OER and HER electrodes demonstrates a high current density of 1500mA cm-2 (OER: 410mV; HER: 240mV), surpassing commercial RuO2 (OER: 600mV) and Pt/C based performance (HER: 265mV).

Site-Selective Plasmonic and Photonic Modulation of Galvanic Replacement Reaction between Silver Nanoprisms and Aqueous Chloroplatinate Ions

Site-Selective Plasmonic and Photonic Modulation of Galvanic Replacement Reaction between Silver Nanoprisms and Aqueous Chloroplatinate Ions

Double-Cabin Galvanic Cell-Synthesizing Nanoporous, Flower-like, Pb-Containing Pd-Au Nanoparticles for Nonenzymatic Formaldehyde Sensor.

In this work, a novel formaldehyde sensor was constructed based on nanoporous, flower-like, Pb-containing Pd-Au nanoparticles deposited on the cathode in a double-cabin galvanic cell (DCGC) with a Cu plate as the anode, a multiwalled carbon nanotube-modified glassy carbon electrode as the cathode, a 0.1 M HClO4 aqueous solution as the anolyte, and a 3.0 mM PdCl2 + 1.0 mM HAuCl4 + 5.0 mM Pb(ClO4)2 + 0.1 M HClO4 aqueous solution as the catholyte, respectively. Electrochemical studies reveal that the stripping of bulk Cu can induce underpotential deposition (UPD) of Pb during the galvanic replacement reaction (GRR) process, which affects the composition and morphology of Pb-containing Pd-Au nanoparticles. The electrocatalytic activity of Pb-containing nanoparticles toward formaldehyde oxidation was examined in an alkaline solution, and the experimental results showed that formaldehyde mainly caused direct oxidation on the surface of Pb-containing Pd-Au nanoparticles while inhibiting the formation of CO poison to a large degree. The proposed formaldehyde sensor exhibits a linear amperometric response to formaldehyde concentrations from 0.01 mM to 5.0 mM, with a sensitivity of 666 μA mM-1 cm-2, a limit of detection (LOD) of 0.89 μM at triple signal-to-noise, rapid response, high anti-interference ability, and good repeatability.