Underpotential Deposition Of Metals Research Articles

Potassium Metal Underpotential Deposition in Crystalline Carbon of Potassium‐Ion Batteries

AbstractCarbon materials, owing to their low cost, high conductivity, and good thermal and chemical stability, have been deemed as a promising anode candidate for potassium‐ion batteries. However, anomalous low‐voltage discharge situations in crystalline carbon materials imply uncertainty in the potassium storage mechanism. Herein, an overlooked scenario, i.e., potassium metal underpotential deposition (PMUPD), is disclosed in crystalline carbon materials for the first time. The study unveils the induction of interlayer pores on desolvation and PMUPD by insights from thermodynamics, kinetics, and experimental analyses. By manipulating the cutoff voltage to utilize partial PMUPD, a novel synergistic mechanism of co‐intercalation and PMUPD is revealed. A remarkable initial coulombic efficiency of 92% and a 65% capacity retention at 30C (80 mAh g−1) are realized in crystalline carbon anode. This work provides a new insight into the potassium storage mechanism of carbon anode and contributes to further research and application of the UPD behavior in other alkaline metal ion batteries.

Cu Surface Chemistry in Acid Media: Vibrational Spectroscopy, Mass Spectrometry and ECSTM Measurements

Copper electrodeposition is a central process in the metallization of microelectronics and more recently copper has also found use as an important electrocatalyst in the conversion of CO2 to hydrocarbons. Gaining mechanistic insight into the reactivity of Cu surfaces requires in situ and better still in operando measurements. Herein the utility of the combination of vibrational spectroscopy (SEIRAS, SHINERS), electrochemical mass spectrometry (EC-MS) and scanning tunneling microscopy (ECSTM) to examine the competitive and co-adsorption interactions between potential dependent halide adsorption, molecular adsorption, underpotential metal deposition and hydride formation on low index Cu single crystals surface will be detailed. Further still, the emergent opportunity to study the impact of such interaction on metal deposition reactions will also be explored.1.Raciti and T.P. Moffat, “Quantification of Hydride Coverage on Cu(111) by Electrochemical Mass Spectrometry,” J. Phys. Chem., 126, 18734-18743 (2022).2.Raciti, A.R. Hight Walker, T. P. Moffat, “Mapping Surface Chemistry During Superfilling with Shell- Isolated Nanoparticle Enhanced Raman Spectroscopy and X-ray Photoelectron Spectroscopy,” J. Electrochem. Soc., 169, 082506 (2022).3.B.M. Tackett, D. Raciti, A.R. Hight Walker, T.P. Moffat, “Surface Hydride Formation on Cu (111) and its Decomposition to Form H2 in Acid Electrolytes,” J. Phys. Chem. Lett., 12, 10936-10941 (2021).4. G.Liu, S. Zou, D. Josell, L.J. Richter and T.P. Moffat, “SEIRAS Study of Chloride Mediated Polyether Adsorption on Cu,” J. Phys. Chem. C., 122, 21933-21951, (2018).

Review on electrochemical active surface area characterization methods of Pt alloy catalysts

<p indent="0mm">Proton exchange membrane fuel cells (PEMFCs) operating at low temperatures and high-power densities are considered one of the most promising technologies for clean energy. However, some fundamental challenges remains to be addressed before PEMFCs can truly become the top contender, high performance with low Pt usage for example. In order to achieve high-performance and cost-effective in PEMFCs, Pt alloy are currently one of the most promising catalyst candidates. Electrochemical active surface area (ECSA) is a key indicator to gauge the performance of Pt catalysts and an important parameter in studying catalytic kinetic issues in PEMFCs. Therefore, the accurate estimation on the ECSA is exceptionally critical. Known and mature ECSA characterization methods for Pt/C catalysts have been established, which has been widely available for many decades. However, there are challenging issues remaining for ECSA characterization of Pt alloy catalysts due to the significant changes in physical structure (composition, particle size, shape, etc.) and chemical properties (active site, catalytic performance, etc.) compared with Pt catalysts. Therefore, the ECSA characterization approaches for Pt/C catalysts cannot be transplanted to Pt alloy catalysts since the characterization accuracy will no longer meet the requirement. In this review, the present methods of ECSA characterization for Pt alloy catalysts and their inaccuracy sources are described and explained, including physical methods and electrochemical methods. Physical methods mainly cover X-ray diffractometry (XRD) and transmission electron microscopy (TEM). hydrogen underpotential deposition (H-upd), carbon monoxide stripping (CO-stripping) and underpotential deposition of metals are classified as electrochemical methods. In XRD and TEM methods, the geometrical areas calculated based on the average particle size is regard as ECSA. In more cases, it is considered to be theoretical ECSA to evaluate the catalyst utilization. Therefore, the ECSA calculated from XRD and TEM is widely used as a reference. Owing to the changes in surface adsorption properties after alloying, it will be underestimated the ECSA of Pt alloy catalysts by H-upd and CO-stripping, which leads to exaggerate specific activity of when compared with Pt/C catalysts. It is generally accepted that sites from electrochemical methods are catalytically active, but it is still a controversy point. The surface area of different metal components of Pt alloy could be quantified by metal underpotential deposition method. Since the contribution of different metal components to the catalytic activity is different, the actual ECSA cannot be simply calculated by adding the respective metal surface area. The surface active of Pt alloy catalysts is affected by many factors, which there is currently not a universal method to characterize the ECSA accurately. To evaluate the performance of Pt alloy catalysts more objectively, it is necessary to clarify the relationship between the surface structure of different Pt alloys and adsorption energy and coverage of adsorbed species, then modifying the calculated equations of ECSA. In addition, to innovatively develop new electrochemical methods with high accuracy is also essential. Such knowledge is in urgent need in order to develop new high-performance Pt alloy catalysts.

Electrochemically Assisted Deposition of Nanoporous Silica Membranes on Gold Electrodes: Effect of 3‐Mercaptopropyl(trimethoxysilane) “Molecular Glue” on Film Formation, Permeability and Metal Underpotential Deposition

AbstractGold electrodes have been covered with vertically aligned mesoporous silica thin films by electro‐assisted self‐assembly. To ensure uniform surface coverage and good adhesion of the membrane to the gold surface, it was necessary to use a (3‐mercaptopropyl)trimethoxysilane (MPTMS) reagent to act as a “molecular glue” thanks to its thiol functionality, which is able to bind to the gold substrate and to its alkoxysilane moieties enabling condensation with the silica material. The MPTMS layer had, however, a significant effect on film permeability to redox species [Ru(NH3)63+ and ferrocenedimethanol (Fc(MeOH)2)]. MPTMS adsorption should be long enough to ensure proper adhesion of the film but not too long so as to avoid surface blocking or film defects; an optimal time window of 60–600 s soaking in 0.1 mM MPTMS in ethanol was evidenced. In addition, Cu underpotential deposition (UPD) experiments revealed that the silica membrane significantly affected the UPD process, suggesting some barrier effect of the porous membrane, but the interface Au/MPTMS/silica is not sharp and allowed metal UPD between the gold substrate and the silica thin film.

(Invited) A Thermodynamic Approach to the First Steps of Metal Deposition

The current response of an electrochemical system to a potential pertubation often contains contributions from many parallel processes. A prominent example is Cu underpotential deposition on Au surfaces, where the Cu deposition is accompanied by the coadsorption of anions. Conventional electrochemical methods like cyclic voltammetry mostly obtain information on the total charge and can therefore not a priori discriminate between the involved processes. Electrochemical microcalorimetry may provide additional, independent information, which may help to identify such processes. By measuring the reversibly exchanged heat during an electrochemical reaction, one directly obtains the reaction entropy of the electrochemical process, including all side reactions. Knowledge of the reaction entropy, together with information from conventional electrochemical methods may thus help to disentangle the elementary steps of an electrochemical process. In this contribution we will give examples for: 1. Anion adsorption on metal surfaces with and without metal underpotential deposition. The dependence of the entropy of the adsorption process for anion adsorption on Au(111) surfaces shows a characteristic variation with potential for all studied anions, which points to an interplay between the configurational entropy of the anion layer and structuring of water at the electrode surface. The entropy data will be corroborated by surface plasmon resonance experiments, which obtained information on the reaction volume of the processes.2. Metal deposition and surface layer formation from metal complexes. The deposition of Ag from Ag-cyanide complexes will be discussed for different CN- Entropy data support the formation of a passivating AgCN layer from [Ag(CN)2]- at low CN- concentrations. The deposition of metallic Ag probably proceeds via direct reduction of [Ag(CN)2]- at all cyanide concentrations.3. The steps of metal deposition from multi valent ions. The elementary steps of Cu deposition from aqueous Cu2+ solutions are studied by time-resolved heat measurements of the deposition process. The data point to a two-step process where the Cu+ - Cu2+ reaction is an electron transfer process in solution, independent of the ion transfer process to metallic Cu at the electrode.

(Invited) Characterization of Mxene/Graphene Supercapacitor Yarns Using Time and Frequency Models

Supercapacitors (SC) turned out to be efficient devices for electrochemical energy storage thanks to their high energy density vs. classical surface capacitors- and high power density vs. batteries. In the absence of electrode components prone to react with the electrolyte, charges are stored in the pore space in a purely capacitive way under the form of electrical double-layer EDL at the solid-liquid interface [1, 2]. In several cases, additional pseudo-capacitive energy storage appears through redox reactions, underpotential deposition of metals or -to a lower extent- to ions intercalation [3]. This may also lead eventually to charge losses. The optimization of supercapacitors can be facilitated using electrode and electrolyte models that capture the physics at the local scale to better understand the charge and mass transfer phenomena governing their behavior. Indeed, SC characterization is still based on relatively simple models based on macroscopic parameters that are generally determined according to voltage evolution during constant current charge and discharge. The electrical equivalent circuit (EEC) often includes only an equivalent series resistance and a capacitance tied up to the average pore population governing their dynamic behavior [1, 2]. In order to account for pore size distribution within the electrodes, EEC consisting of two or more branches of resistances and capacitances in series are sometimes used [1, 2], although some parameters may appear to be correlated. In addition to the charge/discharge behavior, Electrochemical Impedance Spectroscopy (EIS) is another extensively used tool for characterizing electrochemical systems [2, 4]. Since single or multiple branches RC EECs based on surface reaction assumption are not adapted to the frequency domain, SC impedance spectra are usually modelled using Transmission Line Models (TLM) [2, 4] accounting for the volumetric character of the electrodes. TLM are however rarely applied for SC characterization in the time domain, and in the few cases that exist, not under the form of simple analytical expressions [2]. In order to yield a basis for SC modelling and characterization, we present a parameter study comparing different model approaches. They can be applied to purely capacitive and pseudo-capacitive SC with the ultimate objective to derive a model able to capture part of the physics at the local scale and to describe the SC behavior in both the time and frequency domains. As an example we compare the parameters identified in the time and frequency domains on different types of supercapacitor yarns developed by Gao’s group at NCSU [5], including pure double-layer capacitive reduced Graphene Oxide (rGO) yarn SCs and titanium carbide (MXene) – rGO yarn SCs presenting an additional pseudo-capacitive behavior and potentially ion intercalation [3]. In these flexible 2D material based devices, the active components, 2D flakes, are stacked together in distinct morphologies (either smoothly packed with grooves on fiber surfaces, or highly wrinkled via cation crosslinking), wherein different porosity and pore distributions exist. Experimental results as reported by Dr. Gao’s group exhibit dramatically different specific capacitances and rate capabilities. Figure Caption Left: Scheme of the MXene – rGO yarn SC structure; right: Nyquist plot of the MXene-rGO Sc impedance data and interpolation curves obtained with a purely capacitive (dashed line) and a pseudo-capacitive (full line) TLM model.

A phenomenological theory of electrosorption

A phenomenological theory of electrosorption is presented based upon notions of local charge and local electronic polarisability (Friedel oscillations). The strong link between the extent and nature of ionic and molecular adsorption at an electrode surface and the uv-absorption properties displayed by such molecular entities in an aqueous solution is emphasised. The theory may be used to predict, in certain cases the extent of ionic adsorption at the potential of zero charge (PZC) and, also, to rationalise recent results pertaining to metal underpotential deposition (UPD) processes on single crystal electrodes.

Metal Underpotential Deposition to Quantify Defects in 2D Materials

We demonstrate how metal UPD may find use as a general tool to determine the collective defect area in hybrids between 2D materials (graphene, hexagonal boron nitride, etc.) and various substrate metals. By investigating copper UPD on a monolayer of hexagonal boron nitride (h-BN) on Rh(111), we explore how this process can be used to quantify the defects in the h-BN monolayer which form during its chemical vapor deposition. In addition, the UPD signature allows assessing the potential window of the h-BN/metal hybrid, which is important to explore its functionality under ambient and electrochemical conditions. Importantly, UPD itself does not alter the defect area on repeated cycling. Overpotential deposition, on the other hand, is shown to have significant consequences on the defect area. We show that this non-innocent Cu electrodeposition involves intercalation originating at initial defects, causing irreversible delamination of the h-BN layer; this effect therefore may be used for 2D material nanoengineering.

Surface X-ray diffraction studies of single crystal electrocatalysts

In this article we review the contribution of surface X-ray diffraction (SXRD) to the topic of electrocatalysis. Based on several key examples it is shown how SXRD measurements elucidate the atomic structure at the polarised solid-liquid interface which can be used to develop a fundamental understanding of specific electrocatalytic reactions. The review begins with a discussion of single crystal gold electrodes and how the interplay of different adsorbates affects the lifting and formation of the reconstruction. This has given insight into the mechanism of the oxidation reactions on Au(hkl) surfaces. The second part of the review highlights the results obtained on Pt(hkl) single crystal surfaces, specifically the information obtained from SXRD measurements regarding the adsorption and oxidation of carbon monoxide. This includes the effects of anion adsorption, metal underpotential deposition and temperature changes. The third section gives a brief overview of bimetallic surfaces and how SXRD gives crucial information regarding both reactivity and the stability-reactivity relationship. The final section presents an outlook on current and future advances, highlighting the possibility of accessing structural information about the liquid side of the interface and the aim of performing faster SXRD measurements to probe the time domain in electrochemical reactions. The development of experimental setups to study both reactive non-noble metal electrodes and surfaces with specifically engineered atomic geometries and composition for enhanced electrocatalytic reactivity is also described.

High Density Sodium and Lithium Ion Battery Anodes from Banana Peels

Banana peel pseudographite (BPPG) offers superb dual functionality for sodium ion battery (NIB) and lithium ion battery (LIB) anodes. The materials possess low surface areas (19 - 217 m2 g-1) and a relatively high electrode packing density (0.75 g cm-3 vs. ~ 1 g cm-3 for graphite). Tested against Na, BPPG delivers a gravimetric (and volumetric) capacity of 355 mAhg-1 (by active material ~ 700 mAh cm-3, by electrode volume ~ 270 mAh cm-3) after 10 cycles at 50 mAg-1. A nearly flat ~ 200 mAhg-1 plateau that is below 0.1 V, and a minimal charge/discharge voltage hysteresis, makes BPPG a direct electrochemical analogue to graphite but with Na. A charge capacity of 221 mAhg-1 at 500 mAg-1 is degraded by 7% after 600 cycles, while a capacity of 336 mAhg-1 at 100 mAg-1 is degraded by 11% after 300 cycles, in both cases with ~ 100% cycling coulombic efficiency. For LIB applications BPPG offers a gravimetric (volumetric) capacity of 1090 mAhg-1 (by material ~ 2200 mAh cm-3, by electrode ~ 900 mAh cm-3) at 50 mAg-1. The reason that BPPG works so well for both NIBs and LIBs is that it uniquely contains three essential features: a) dilated intergraphene spacing for Na intercalation at low voltages; b) highly accessible near-surface nanopores for Li metal filling at low voltages; and c) substantial defect content in the graphene planes for Li adsorption at higher voltages. The < 0.1 V charge storage mechanism is fundamentally different for Na versus for Li. A combination of XRD and XPS demonstrates highly reversible Na intercalation rather than metal underpotential deposition. By contrast, the same analysis proves the presence of metallic Li in the pores, with intercalation being much less pronounced.

Underpotential shift in electrodeposition of metal adlayer on tellurium and the free energy of metal telluride formation

Underpotential deposition (UPD) of metals on polycrystalline tellurium film shows much similarity with UPD of metals on foreign metals, but the underpotential shifts on tellurium show no correlation with differences of work functions of the substrate and the deposited metal. In this work, we have evaluated the underpotential shifts of Pb, Cd, Zn, Bi, In, Sn, and Cu UPD on tellurium from cyclic voltammograms and potentiodynamic profiles of inverse charge transfer resistance derived from potentiodynamic impedance spectra, and shown a correlation of the underpotential shifts with the free energy of the corresponding metal telluride formation. The correlation can help to predict underpotential shifts for metals with complications in the measurement of this parameter.

Origin of non-SEI related coulombic efficiency loss in carbons tested against Na and Li

Partially ordered but not graphitized carbons are widely employed for sodium and lithium ion battery (NIB and LIB) anodes, either in their pure form or as a secondary supporting phase for oxides, sulfides and insertion electrodes. These “pseudographitic” materials ubiquitously display a poor initial coulombic efficiency (CE), which has been historically attributed to solid electrolyte interface (SEI) formation on their large surface areas (up to ∼2500 m2 g−1). Here we identify the other sources CE loss by examining a pseudographitic carbon with a state-of-the-art capacity (>350 mA h g−1 for NIB, >800 mA h g−1 for LIB), but with a purposely designed low surface area (14.5 m2 g−1) that disqualifies SEI from having a substantial role. During the initial several (<5) cycles both Na and Li are irreversibly trapped in the bulk, with the associated CE loss occurring at higher desodiation/delithiation voltages. We measure a progressively increasing graphene interlayer spacing and a progressively increasing Raman G band intensity, indicating that the charge carriers become trapped not only at the graphene defects but also between the graphene planes hence causing them to both dilate and order. For the case of Li, we also unambiguously detected irreversible metal underpotential deposition (“nanoplating”) within the nanopores at roughly below 0.2 V. It is expected that in conventional high surface area carbons these mechanisms will be a major contributor to CE loss in parallel to classic SEI formation. Key implications to emerge from these findings are that improvements in early cycling CE may be achieved by synthesizing pseudographitic carbons with lower levels of trapping defects, but that for LIBs the large cycle 1 CE loss may be unavoidable if highly porous structures are utilized.

Underpotential deposition: From planar surfaces to nanoparticles

Abstract An overview is given of selected theoretical, experimental and computer simulation research on thermodynamic modeling applied to the metal underpotential deposition. Focus is made mainly on the last 20 years. The upd -theory on planar surfaces is revisited and the thermodynamic framework is extended to consider underpotential deposition on nanoparticles and to include anion coadsorption, solvation and double layer charging. Results from molecular dynamics and Monte Carlo simulations are shown for systems of experimental interest. At the end some perspectives for further advanced modeling of the present problem are given.

High-density sodium and lithium ion battery anodes from banana peels.

Banana peel pseudographite (BPPG) offers superb dual functionality for sodium ion battery (NIB) and lithium ion battery (LIB) anodes. The materials possess low surface areas (19-217 m(2) g(-1)) and a relatively high electrode packing density (0.75 g cm(-3) vs ∼1 g cm(-3) for graphite). Tested against Na, BPPG delivers a gravimetric (and volumetric) capacity of 355 mAh g(-1) (by active material ∼700 mAh cm(-3), by electrode volume ∼270 mAh cm(-3)) after 10 cycles at 50 mA g(-1). A nearly flat ∼200 mAh g(-1) plateau that is below 0.1 V and a minimal charge/discharge voltage hysteresis make BPPG a direct electrochemical analogue to graphite but with Na. A charge capacity of 221 mAh g(-1) at 500 mA g(-1) is degraded by 7% after 600 cycles, while a capacity of 336 mAh g(-1) at 100 mAg(-1) is degraded by 11% after 300 cycles, in both cases with ∼100% cycling Coulombic efficiency. For LIB applications BPPG offers a gravimetric (volumetric) capacity of 1090 mAh g(-1) (by material ∼2200 mAh cm(-3), by electrode ∼900 mAh cm(-3)) at 50 mA g(-1). The reason that BPPG works so well for both NIBs and LIBs is that it uniquely contains three essential features: (a) dilated intergraphene spacing for Na intercalation at low voltages; (b) highly accessible near-surface nanopores for Li metal filling at low voltages; and (c) substantial defect content in the graphene planes for Li adsorption at higher voltages. The <0.1 V charge storage mechanism is fundamentally different for Na versus for Li. A combination of XRD and XPS demonstrates highly reversible Na intercalation rather than metal underpotential deposition. By contrast, the same analysis proves the presence of metallic Li in the pores, with intercalation being much less pronounced.

Generation of Active Sites on Gold Nanostructured Surface through Ultrasound‐Assisted Direct Electrodeposition and Its Effect on Enzyme‐less Glucose Electro‐oxidation

AbstractBy using ultrasound‐assisted direct electrodeposition, gold nanostructured films decorated by catalytic sites can be generated that are capable of effecting enzyme‐less oxidation of glucose at pH 7.4. The morphology, surface roughness and nature of the crystallographic orientation of the deposited gold nanoparticles on a glassy carbon electrode surface are studied by atomic force microscopy and metal underpotential deposition. The cyclic voltammetry signatures of the deposited nanostructured gold films reveal the identity of the catalytically active sites, which undergo pre‐monolayer oxidation/reduction on the nanostructured gold surface. These active species are responsible for the electrocatalytic oxidation of glucose under neutral pH conditions, enabling a steady‐state amperometric response in a linear range of concentration from 0.25 to 1.75 mM with a sensitivity of 0.849×10−3 mA cm−2 mM−1.

A general model of metal underpotential deposition in the presence of thiol-based additives based on an in situ STM study

Bis(3-sulfopropyl)disulfide (SPS) is a common additive in commercial copper electroplating baths. We have studied the influence of SPS on Cu underpotential deposition (UPD) on a Au(111) single crystal surface by means of cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (EC-STM). By combining our results with the results from the literature we propose a model that describes different stages of Cu UPD in the presence of SPS. Further analysis shows that our model is also applicable to a more general case of UPD of different metals, e.g. Cu and Ag, on a thiol-modified single-crystal surface, where the bond between the substrate and the thiol is adatom mediated. In addition, we have verified our model by in situ observation of the lifting of the Herringbone reconstruction on the Au(111) surface by Cu UPD.

Electrochemistry at synchrotrons

Synchrotron techniques (X-ray and far infrared) have been used in electrochemical research for about the last 25 years. They are powerful new tools to investigate in situ the structure of the electrochemical interphase extending a few thousand angstrom in both phases around the solid/liquid interface. A brief description of the experimental techniques is given, with numerous examples of their applications to investigate a wide variety of phenomena, including measurements of the roughness of electrode surfaces such as relaxation/reconstruction of metal surfaces, the structure of the electrochemical double layer, adsorption/absorption at electrode surfaces, oxide film formation on metals and passivation, underpotential deposition of metals, electrode structures/compositions in batteries and fuel cells, and porous electrode surfaces such as anodic formation of porous silicon. Some historical notes and personal reminiscences are also included.

A Minimally Arbitrary Numerical Method for the Separation of Faradaic and Background Currents of Interest

Various self-limiting adsorptive processes occur that modify the electrode―electrolyte interface in a well-defined way. A few of these processes include reductive desorption of self-assembled monolayers, underpotential deposition of metals, and oxidation of adsorbed CO. The characterization of these systems requires determining the adsorbate coverage. The most common electrochemical technique for this is to perform voltammetry on the adlayer, which is integrated to obtain the charge. However, to obtain accurate coverages, it is necessary to subtract background currents due to unrelated processes. The development and application of a minimally arbitrary numerical background subtraction scheme is the subject of this article.

Underpotential Deposition of Metals — Progress and Prospects in Modeling

AbstractFor Abstract see ChemInform Abstract in Full Text.

Estimation of electrochemical quartz crystal microbalance frequencies from cyclic voltammetric data:—underpotential deposition of metals as an illustration

The estimation of electrochemical quartz crystal microbalance (EQCM) frequencies from a given cyclic voltammetric data is analysed using underpotential deposition (UPD) of metals as an illustrative process. The crucial role played by the surface roughness of electrodes and electrosorption valency of the depositing species is pointed out. The computed EQCM frequency shifts for the UPD of Cd and Tl on polycrystalline Ag electrodes are in satisfactory agreement with the experimental data.