Electrochemical characterization of p-type semiconducting tungsten disulfide photocathodes: efficient photoreduction processes at semiconductor/liquid electrolyte interfaces

Journal Article · Wed Apr 20 04:00:00 EST 1983 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00346a024· OSTI ID:5718371

Bagilo, J A; Calabrese, G S; Harrison, D J; Kamieniecki, E; Ricco, A J; Wrighton, M S; Zoski, G D

Single-crystal p-type WS/sub 2/(E/sub g/ approx. = 1.3 eV) has been synthesized and characterized as an electrode material in CH/sub 3/CN/0.1 M (n-Bu/sub 4/N)ClO/sub 4/ and in aqueous electrolytes containing a variety of one-electron redox reagents having different E/sub 1/2/ values. In either CH/sub 3/CN or H/sub 2/O solvent the flat-band potential, E/sub FB/, is measured to be approx. + 0.95 vs SCE. In aqueous I/sub 3//sup -//I/sup -/ the E/sub FB/ is shifted more negatively by at least 0.3 V as is found for n-type WS/sub 2/ photoanodes. Capacitance measurements of the WS/sub 2//electrolyte interface to determine E/sub FB/ accord well with electrochemical measurements. For E/sub 1/2/ more negative than E/sub FB/ the p-type WS/sub 2/ behaves as a photocathode giving an open-circuit photovoltage, E/sub v/(oc), up to approx. 0.8 V depending on E/sub 1/2/. For E/sub 1/2/ between +1.3 and -0.1 V vs SCE, E/sub v/(oc) varies as expected: for E/sub 1/2/ more positive than E/sub FB/ the p-type WS/sub 2/ behaves as a metallic electrode while for E/sub 1/2/ more negative than E/sub FB/ we find E/sub v/(oc) approx. = vertical bar E/sub 1/2/ - E/sub FB/ vertical bar. It appears that for negative redox couples carrier inversion results at the p-WS/sub 2/ surface, but for E/sub 1/2/ more negative than -0.1 V vs SCE E/sub v/(oc) declines, a result associated with junction breakdown at sufficiently negative potentials. p-Type WS/sub 2/-based photoelectrochemical cells can be used to effect the sustained conversion of visible light (632.8 nm) to electricity in H/sub 2/O or CH/sub 3/CN with efficiencies of up to approx. 7%. In H/sub 2/O the photochemical reduction to H/sub 2/ can be effected by illumination of p-type WS/sub 2/ modified by depositing approx. 10/sup -7/ mol/cm/sup 2/ of Pd(0) or Pt(0) onto the surface as an H/sub 2/ evolution catalyst. Efficiency for H/sub 2/ evolution from 6 M H/sub 2/SO/sub 4/ is typically 6 to 7% for 632.8 nm (50 mW/cm/sup 2/) intensity.

• OSTI ID: 5718371
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 105:8; ISSN JACSA
• Country of Publication: United States
• Language: English

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