Mechanism of electrochemical reduction of hydrogen peroxide on copper in acidic sulfate solutions.

Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Langmuir (Impact Factor: 4.38). 10/2007; 23(19):9911-8. DOI: 10.1021/la7013557
Source: PubMed

ABSTRACT Hydrogen peroxide is a commonly used oxidizer component in chemical mechanical planarization slurries, used in the processing of Cu metallization in microelectronics applications. We studied the electrochemical reduction of hydrogen peroxide on Cu in 0.1 M H2SO4 solutions using methods including cyclic voltammetry, rotating disk electrode experiments, surface-enhanced Raman spectroscopy, and density functional theory (DFT) calculations. The spectroscopy reveals that the hydrogen peroxide molecule is reduced at negative potentials to form a Cu-OH surface species in acidic solutions, a result consistent with the insight from Tafel slope measurements. DFT calculations support the instability of peroxide relative to the surface-coordinated hydroxide on both Cu(111) and Cu(100) surfaces.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Chemical mechanical planarization/polishing (CMP) of copper has emerged as an important component in semiconductor processing. It involves both chemical and mechanical effects, consisting of several steps such as passivation, film dissolution, chemical corrosion, and abrasive abrasion. It is important to understand the individual steps in the removal process. In this paper, investigations were focused on the tribo-chemical behavior of copper in hydrogen peroxide solution at different pH values. The repassivation current and friction coefficient were measured in situ as a function of time. The compositions of unworn and worn surfaces after the tribocorrosion experiments were also analyzed by Raman spectra. The copper exhibited a tendency of repassivation during the potentiostatic tests; furthermore, the repassivation kinetics varied with the surface species and the quantity of passive films formed at different pH values. The results indicate that both relatively high material removal rate and good surface quality may be achieved in the weak acidic solution during CMP.
    Tribology Letters 05/2013; 50(2). · 2.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The fabrication of titanate (TiO2) hollow nanospheres (HNSs), based on the template-directed deposition method at 30 °C temperature, has been developed in pure water using carbon nanosphere templates and TiF4 as a precursor. The diameter of the TiO2 HNS was about 200 nm, constructed by the aggregation of TiO2 nanoparticles with a size of about 20 nm. TiO2 HNSs were characterized by Fourier transform infrared spectra, X-ray diffraction pattern, energy-dispersive X-ray pattern, field emission scanning electron microscope, and high-resolution transmittance electron microscope. The TiO2 HNS-modified glassy carbon electrodes showed excellent electrocatalytic activity for the reduction of hydrogen peroxide, sensing of ethanol, and the oxidation of antioxidants such as dopamine, ascorbic acid, propyl gallate and tert-butylhydroxyanisole, with less oxidation and reduction potential. These electrochemical properties were carried out using cyclic voltammetry in the presence of 0.1 M KCl (pH 5.9).
    Journal of Solid State Electrochemistry 01/2013; 17(8):2173 - 2182. · 2.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH4) as the fuel, and hydrogen peroxide (H2O2) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space and underwater applications, where air is not available and gas storage poses obvious problems. One key factor to improve the performance of DBFCs concerns the type of separator used. Both anion- and cation-exchange membranes may be considered as potential separators for DBFC. In the present paper, the effect of the membrane type on the performance of laboratory NaBH4/H2O2 fuel cells using Pt electrodes is studied at room temperature. Two commercial ion-exchange membranes from Membranes International Inc., an anion-exchange membrane (AMI-7001S) and a cation-exchange membrane (CMI-7000S), are tested as ionic separators for the DBFC. The membranes are compared directly by the observation and analysis of the corresponding DBFC's performance. Cell polarization, power density, stability, and durability tests are used in the membranes' evaluation. Energy densities and specific capacities are estimated. Most tests conducted, clearly indicate a superior performance of the cation-exchange membranes over the anion-exchange membrane. The two membranes are also compared with several other previously tested commercial membranes. For long term cell operation, these membranes seem to outperform the stability of the benchmark Nafion membranes but further studies are still required to improve their instantaneous power load.
    Membranes. 01/2012; 2(3):478-92.