title: Hydrogen evolution from Pt/Ru-coated p-type WSe2 photocathodes.
abstract: Crystalline p-type WSe(2) has been grown by a chemical vapor transport method. After deposition of noble metal catalysts, p-WSe(2) photocathodes exhibited thermodynamically based photoelectrode energy-conversion efficiencies of >7% for the hydrogen evolution reaction under mildly acidic conditions, and were stable under cathodic conditions for at least 2 h in acidic as well as in alkaline electrolytes. The open circuit potentials of the photoelectrodes in contact with the H(+)/H(2) redox couple were very close to the bulk recombination/diffusion limit predicted from the Shockley diode equation. Only crystals with a prevalence of surface step edges exhibited a shift in flat-band potential as the pH was varied. Spectral response data indicated effective minority-carrier diffusion lengths of ∼1 μm, which limited the attainable photocurrent densities in the samples to ∼15 mA cm(-2) under 100 mW cm(-2) of Air Mass 1.5G illumination.
authors.affiliation: Division of Chemistry and Chemical Engineering and the Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 East California Blvd, Pasadena, California 91125, United States.
authors.forename: James R
authors.initials: JR
authors.lastname: McKone
authors.forename: Adam P
authors.initials: AP
authors.lastname: Pieterick
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Lewis