An official website of the United States government
Abstract Synthesis of intermetallic crystals by electrodeposition of Ag from alkaline aqueous electrolytes containing AgCN onto liquid metal electrodes via an electrochemical liquid‐liquid‐solid (ec‐LLS) process has been performed. X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy were performed to identify crystalline products. Ec‐LLS experiments performed with pure liquid Hg and Ga electrodes resulted in the formation of polycrystalline Ag2Ga and Ag2Hg3. Experiments performed with In‐containing liquid metals preferentially yielded Ag9In4and AgIn2products with liquid Hg0.35In0.65and Ga0.86In0.14, respectively. The product distribution with liquid Hg0.35In0.65depended on the level of Ag supersaturation during the electrodeposition. A mechanism that accounts for the aforementioned observations is presented and discussed. This work described the formation of Ag−In intermetallic phases by the isothermal electroreduction of Ag into different liquid metal solvents via ec‐LLS. Electrodeposition of Ag into a pure Ga or pure Hg liquid metal pool yielded precisely the compounds predicted from isothermal cross‐sections of the respective binary phase diagrams. These compounds were not found when using liquid Hg or Ga containing appreciable In. The smaller enthalpy of formation for AgIn2was consistent with its synthesis in Ga0.86In0.14. However, the observed product of Ag9In4in Hg‐containing liquid metals could not be rationalized solely from thermodynamic factors. Instead, this observation was consistent with a kinetic pathway based on the lability of Hg‐metal bonds and nearly identical crystal structures of Ag9In4and Ag2Hg3. Site exchange of Hg for In is consistent with our prior observations[23]of In exchange into Hg−Pd structures during Pd electrodeposition. This mechanism is not based on any direct role of electrochemistry other than aspects that dictate the operative supersaturation of the metal solute.
more »
« less
Electroreduction of Perchlorinated Silanes for Si Electrodeposition
The electrochemical reactivity and suitability of hexachlorodisilane and tetrakis(trichlorosilyl)silane as Si ec-LLS electrodeposition precursors in several electrolyte solutions have been investigated. Voltammetric data indicated that perchlorinated silanes exhibit mechanistically similar electrochemical responses as SiCl4, regardless of the Si–Si bond content in the precursor. The voltammetric responses were a strong function of the concentration of the precursor, indicating the participation of electrogenerated intermediates during the reduction and concomitant Si electrodeposition. Variation of the anion in the supporting electrolyte was found to be a critical factor for the thermal and chemical stability of the precursor bath. A combination of chronoamperometry and electron microscopy data were used to study the deposition efficiency specifically for hexachlorodisilane. The faradaic efficiency was low, regardless of overpotential or the composition of the electrolyte. Cumulatively, these data show that while larger chlorosilanes can be used for conventional Si electrodeposition over a wider range of conditions, their chemical instability and propensity for low faradaic efficiency limit their utility as reagents relative to SiCl4for Si electrodeposition by ec-LLS.
more »
« less
- Award ID(s):
- 1807755
- PAR ID:
- 10303715
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 168
- Issue:
- 2
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- Article No. 022503
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Light addressable electrochemical (LAE) sensors have seen great utility in the past several years because they enable multiple localized electrochemical measurements to be performed on a single macroscopic electrode, opening up applications in imaging, biosensing, surface patterning, and multiplexing. In this study, we investigated the effects of electrodeposition on the formation of LAE sensors formed between n‐Si and electrodeposited Pt. We prepared sensors by electrodepositing Pt onto freshly‐etched n‐Si under a variety of conditions, varying the Pt precursor concentration, electrodeposition time, supporting electrolyte, and potential waveform. We characterized the sensors using a combination of atomic force microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. This study shows that the electrodeposition parameters have a dramatic impact on the morphology of the electrodeposited surfaces, sensor stability, and sensitivity towards H2O2. Specifically, we observed that continuous Pt films prepared with a higher Pt precursor concentration were more stable and had better linearity, higher sensitivity, and broader dynamic range than those prepared with a lower Pt precursor concentration. The stability and increased H2O2sensing performance correlate strongly with an increase in the Pt islands which make up the film. These data highlight that the morphology of the metal in semiconductor/metal junction LAE sensors has an impact on important performance metrics like stability and sensitivity. They also demonstrate the need for semiconductor/metal LAE sensors to be studied using micro‐ and nanoscale imaging techniques in order to more deeply understand their performance characteristics.more » « less
-
Electrodeposition of Pd Intermetallics using Hg-In by the Electrochemical Liquid-Liquid-Solid MethodElectrodeposition of Pd from alkaline baths containing Pd(CN) 2 and KCN with liquid metal electrodes has been performed. Data are presented that Pd dissolved into and reacted with the liquid metal electrodes via an electrochemical liquid-liquid-solid (ec-LLS) process. HgPd crystals were obtained with liquid Hg electrodes. On solid In electrodes, In 7 Pd 3 was exclusively formed. In contrast, InPd was the primary product with Hg 1-x In x alloy electrodes. X-ray diffraction, scanning electron microscopy, and electron backscattering diffraction show that the materials were not a pure phase, as minor components of HgPd and In 7 Pd 3 were observed for various liquid Hg-In compositions. A mechanism is proposed where the InPd intermetallic forms through an intermediate phase of HgPd by the substitution of In atoms for the Hg sites of the unit cell. This study thus motivates further exploration of Hg 1-x In x as a versatile medium for intermetallic synthesis by ec-LLS.more » « less
-
Abstract Despite the advantages of aqueous zinc (Zn) metal batteries (AZMB) like high specific capacity (820 mAh g−1and 5,854 mAh cm−3), low redox potential (−0.76 V vs. the standard hydrogen electrode), low cost, water compatibility, and safety, the development of practically relevant batteries is plagued by several issues like unwanted hydrogen evolution reaction (HER), corrosion of Zn substrate (insulating ZnO, Zn(OH)2, Zn(SO4)x(OH)y, Zn(ClO4)x(OH)yetc. passivation layer), and dendrite growth. Controlling and suppressing HER activity strongly correlates with the long‐term cyclability of AZMBs. Therefore, a precise quantitative technique is needed to monitor the real‐time dynamics of hydrogen evolution during Zn electrodeposition. In this study, we quantify hydrogen evolution using in situ electrochemical mass spectrometry (ECMS). This methodology enables us to determine a correction factor for the faradaic efficiency of this system with unmatched precision. For instance, during the electrodeposition of zinc on a copper substrate at a current density of 1.5 mA/cm2for 600 seconds, 0.3 % of the total charge is attributed to HER, while the rest contributes to zinc electrodeposition. At first glance, this may seem like a small fraction, but it can be detrimental to the long‐term cycling performance of AZMBs. Furthermore, our results provide insights into the correlation between HER and the porous morphology of the electrodeposited zinc, unravelling the presence of trapped H2and Zn corrosion during the charging process. Overall, this study sets a platform to accurately determine the faradaic efficiency of Zn electrodeposition and provides a powerful tool for evaluating electrolyte additives, salts, and electrode modifications aimed at enhancing long‐term stability and suppressing the HER in aqueous Zn batteries.more » « less
-
Many studies have investigated the conversion of biomass derivatives to value-added products. However, the influence of different factors on the reaction outcomes of these often-complex systems is not well understood. Herein, a statistical design of experiments—specifically, response surface methodology—is applied to the glycerol electrooxidation reaction in a flow electrolyzer. Four operational variables (glycerol concentration, NaOH concentration, flow rate, and catalyst loading) were investigated for their effects on measurable responses of the electrochemical reaction: current density and Faradaic efficiency to a given product. Independent optimizations of current density and Faradaic efficiency, as well as simultaneous optimization of both, were investigated. Each optimization was evaluated using response surface coefficients to analyze sensitivity and simulated runs to visualize the parameter space. These evaluations revealed contradictions in operating conditions required to simultaneously maximize current density and Faradaic efficiency to C3products glycerate and lactate, leading to low current densities and Faradaic efficiencies. However, simultaneously maximizing current density and Faradaic efficiency to C1product formate led to high current densities and Faradaic efficiencies. These insights guide tuning GEOR production to maximize overall reactor performance. Furthermore, this study outlines a framework for experimental evaluation and optimization of other electrolysis chemistries.more » « less
