Boosting PEC performance of Si photoelectrodes by coupling bifunctional CuCo hybrid oxide cocatalysts

Silicon (Si) is an attractive candidate for photoelectrochemical (PEC) water splitting because of its small band gap, fast carrier mobility and abundant reserves. However, the PEC performance has been severely limited by the sluggish kinetics of oxygen/hydrogen evolution reaction at the Si photoelectrode/electrolyte interface and poor stability in the aqueous environment. Herein, the bifunctional CuCo hybrid oxides (CuCo-HO) cocatalysts have been integrated with ultrathin TiO2 decorated n-type and p-type Si nanowires (NWs) to simultaneously improve the photoactivity and stability of Si photoelectrodes. The thickness of TiO2 layer, the concentration of CuCo-precursor and the hydrothermal reaction time have been investigated to optimize the PEC performance. The enhancement mechanism is studied and mainly ascribed to the increased light harvesting, small charge transfer resistance and high carrier density of Si NWs/TiO2/CuCo-HO photoelectrodes.