Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Abstract

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV.

Electrodes Based on Se Anchored on NiCoP and Carbon Nanofibers for Flexible Energy Storage Devices

“…The peak centered at 61.73 eV indicates the oxidation state of Se VI . The overall binding energy of Se species appears to be slightly positively shifted compared to that of bare Se, which indicates effective charge transfer from the carbon template to the electroactive centers via the Se interface . Moreover, inside the Se spectrum, Ni 3p is centered at 67.17 and 69.32 eV for Ni 3p 1/2 and Ni 3p 3/2 , respectively, and this may be due to the presence of Ni 2+ and partially oxidized Ni 3+ species.…”

Se-Incorporated Porous Carbon/Ni5P4 Nanostructures for Electrocatalytic Hydrogen Evolution Reaction with Waste Heat Management

“…The corresponding peaks of Se­(IV) with energy levels 3d 5/2 and 3d 3/2 at 59.20 and 59.90 eV represent the formation of SeO x followed by the oxidation of selenium upon interaction with air. The peaks at 51.67 and 52.24 eV for energy levels 3d 5/2 and 3d 3/2 , respectively, indicate the formation of Se­(-II) species such as HSe – and H 2 Se with the hydrazine hydrate or the bond formation with the carbon as well as Ni. For the C 1s energy level, three peaks are clearly observed at 284.63, 286.16, and 289.63 eV in the MF-Gr-CNTs-Se-Ni 5 P 4 system (Figure d), which can be assigned to sp 2 hybridized graphite-like carbon atoms (C–C) and carbon atoms bound to one oxygen atom by a single bond and a double bond (C–O–C/OC–O), respectively .…”

“…The high-resolution Se 3d spectrum corresponds to five peaks for the variable oxidation states of Se, such as Se(0), Se(-II), and Se(IV) (Figure 4c). The peaks at 55.12 and 56.2 eV have been assigned to Se(0), where a slight shift toward a higher binding energy as compared to bare Se(0) 42 illustrates the transfer of electrons from Se to the carbonaceous matrix as well as Ni 5 P 4 , referring to the bridging characteristics of Se. However, the Se(0) peak was slightly upshifted from 55.04 to 55.12 eV for 3d 5/2 and from 56.00 to 56.2 eV for 3d 3/2 for Ni 5 P 4 nanostructures decorated on MF-Gr-CNTs-Se as compared to the bare MF-Gr-CNTs-Se structure (shown in Figure S13a).…”

“…5/2 and 3d 3/2 , respectively, indicate the formation of Se(-II) species such as HSe − and H 2 Se with the hydrazine hydrate42 or the bond formation with the carbon as well as Ni. For the C 1s energy level, three peaks are clearly observed at 284.63, 286.16, and 289.63 eV in the MF-Gr-CNTs-Se-Ni 5 P 4 system (Figure4d), which can be assigned to sp 2 hybridized graphite-like carbon atoms (C−C) and carbon atoms bound to one oxygen atom by a single bond and a double bond (C−O−C/OC− O), respectively 8.…”

Effect of EDTA Complexation on the Kinetics and Thermodynamics of Uranium Redox Reactions Catalyzed by Pyrite: A Combined Electrochemical and Quantum-Mechanical Approach

“…In this study, a combination of electrochemical methods and quantum-mechanical calculations are used to study the effect of EDTA complexation on the kinetics of uranium redox reactions mediated by pyrite surfaces. The electrochemical approach involves a pyrite-powder microelectrode, ,,, not only to evaluate uranium redox processes occurring in situ under various solution conditions but also to control the reaction rate of uranium species by changing the scan rate of the electrochemical potential. This helps estimate the effect of EDTA complexation on the redox reaction rate of uranium on the pyrite surface.…”