Efficient and stable photoelectrochemical energy conversion using p-type WSe2 photocathodes implications

We have synthesized highly cryst. p-type WSe2 and characterized its electrochem. and photoelectrochem. behavior in a variety of aq. redox couples. Energy conversion efficiencies of > 7% with respect to the thermodn. potential for hydrogen evolution have been achieved for p-WSe2 photocathodes deposited with a mixed Ru/Pt cocatalyst under 100 mW cm^(-2) white light illumination. Addnl., these photocathodes exhibit good stability during photoredn. of Me viologen for at least two hours under illumination at pH values of 2 and 10. Spectral response measurements suggest that energy conversion efficiencies are limited by short minority-carrier diffusion lengths, but impedance spectroscopy indicates that the p-WSe2 band-edge positions are nearly ideal for attaining max. photovoltages for the hydrogen evolution reaction.