Electron‐Selective TiO₂ /CVD‐Graphene Layers for Photocorrosion Inhibition in Cu₂O Photocathodes

Abstract

Mitigating photocorrosion in the light absorber material used for photoelectrochemical solar water splitting is a subject of major research. In this work, a systematic investigation is carried out on suppressing the photocorrosion in an electrodeposited Cu 2 O photocathode using stable protective layers. The photocathode protected with chemical vapor deposited graphene offers significant stability, till 600 s during light chopping chronoamperometry. However, the presence of a few microcracks in the graphene layer cannot offer complete protection, and causes a gradual decay in the photocurrent. The addition of an ultrathin layer (≈10 nm) of amorphous TiO 2 on top of the graphene blocks the microcracks, thereby resulting in complete protection to the Cu 2 O absorber layer. The TiO 2 /graphene protected Cu 2 O photocathode generates ‐3 mA cm −2 photocurrent at 0.0 V versus reversible hydrogen electrode under 1 sun in 1 m Na 2 SO 4 electrolyte (pH 7), which is twice that compared to the bare Cu 2 O electrode. The enhancement in photocurrent can be attributed to the ease of separating the photogenerated charge carriers due to the suitable band alignment and electron selective nature of the protective TiO 2 /graphene layers.