A heteroelectrode structure for solar water splitting: Integrated cobalt ditelluride across a TiO₂-passivated silicon microwire array

Cobalt ditelluride as a cocatalyst on the surface of a silicon microwire array (Si-MWs) and as a heterocathode structure for the hydrogen evolution reaction was synthesized via a one-step drop-casting method. The improvement in the photo-electrocatalytic efficiency, including the 0.66 V anodic shift in the onset potential and the -24.0 mA cm^-2 photocurrent density, is comparable to that of other cocatalyst systems for water reduction. The photocurrent decay of CoTe₂@Si-MWs further improved to roughly -10 mA cm^-2 by deposition of 10 nm atomic-layer-deposited TiO₂ on the Si-MW photocathode for 67 min. Outcomes of this study may demonstrate the possibility of introducing a new class of telluride cocatalyst heterocathode system as an alternative to noble metals in facilitating the water splitting reaction. The cobalt ditelluride across the TiO₂-passivated Si-MWs heterocathode is reported to have an effective response to solar water reduction for the first time.