Using TiO2 as a Conductive Protective Layer for Photocathodic H2 Evolution

• DOI: 10.1021/ja309523t
• Publication Date: 2013-01-04T22:40:41Z
• Authors: Brian Seger; Thomas Pedersen; Anders B. Laursen; Peter C. K. Vesborg; Ole Hansen; Ib Chorkendorff
• Keywords: Photocathode; Passivation; Photocurrent; Photoelectrochemistry

Surface passivation is a general issue for Si-based photoelectrodes because it progressively hinders electron conduction at the semiconductor/electrolyte interface. In this work, we show that sputtered 100 nm TiO2 layer on top of thin Ti metal may be used to protect an n+p Si photocathode during photocatalytic H2 evolution. Although semiconductor, behaves like metallic conductor would under photocathodic evolution conditions. This behavior due fortunate alignment band with respect hydrogen potential, which allows conduct electrons from while simultaneously protecting surface passivation. By using Pt catalyst electrode achieves onset 520 mV vs NHE and Tafel slope 30 when illuminated by red part (λ > 635 nm) AM 1.5 spectrum. The saturation photocurrent (H2 evolution) was also significantly enhanced antireflective properties layer. It shown proper annealing conditions these electrodes could run 72 h without significant degradation. An Fe2+/Fe3+ redox couple help elucidate details diagram.