Cadmium cathodic deposition on polycrystalline p-selenium: Dark and photoelectrochemical processes |
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Authors: | GA Ragoisha EA Streltsov SM Rabchynski DK Ivanou |
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Affiliation: | aResearch Institute for Physical Chemical Problems, Belarusian State University, Leningradskaya 14, Minsk 220030, Belarus;bChemistry Department, Belarusian State University, Minsk 220030, Belarus |
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Abstract: | Cathodic reduction of Cd2+ on p-Se proceeds at low overpotential in the dark and results in bulk Cd, while the underpotential deposition is kinetically inhibited. Cadmium adlayer is photoelectrochemically deposited on illuminated electrode 0.7 V above E(Cd2+/Cd). The adlayer cathodic deposition under illumination proceeds with simultaneous formation of CdSe nanoparticles. Potentiodynamic electrochemical impedance spectroscopy has discriminated the two products of the photoelectrochemical reaction both by their potentials of anodic oxidation and by characteristic dependences of impedance on potential. Anodic oxidation of CdSe nanoparticles gives a sharp peak of real impedance in low frequencies close to the corresponding anodic current peak in cyclic voltammogram. The impedance peak appears below a threshold frequency ft. The latter separates two modes of diffusion in anodic dissolution of CdSe nanoparticles. The diffusion proceeds independently at different particles above ft and turns to cooperative mode below the threshold frequency. Due to this effect, information on spatial distribution of growing nuclei on electrode surface in early stages of electrodeposition can be obtained from potentiodynamic impedance spectra. |
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Keywords: | Cadmium Selenium CdSe Underpotential deposition Potentiodynamic electrochemical impedance spectroscopy |
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