| 초록 |
TiO2 films typically prepared by atomic layer deposition (ALD) have been widely used to produce Cu2O nanowire-based photocathodes with photoelectrochemical (PEC) durability, and this approach allows conformal coatings and provides chemical robustness. However, this general approach requires complex interlayers such as Al-doped ZnO films and makes it difficult to produce photocathodes with reproducible performance and long-time stability. Although Sol-gel coating methods have been studied for oxide passivation mainly for PEC applications because they are heavily influenced by surface chemical bonding, but they have been mainly demonstrated on flat substrates. As a unique strategy based on solution processing, herein, we suggest a creative solution for two problems encountered in the conformal coating of surfaces with oxide layers: i) how to effectively prevent corrosion of materials with hydrophilic surfaces by using a single TiO2 passivation layer, instead of a multilayer structure, and ii) guaranteeing perfect chemical durability. Cu(OH)2 nanowires can be easily prepared as an intermediate phase by anodization of copper metal, where the former inherently possess a hydrophilic hydroxylated surface, and thus enables conformal coating with TiO2 precursor solutions. Then chemically robust nanowires are generated as the final product via phase transformation of Cu(OH)2 to Cu2O via sintering at 600 °C. The coated nanowires show excellent photoelectrochemical properties and stable performance without using photocatalysts and interlayers. As a result, this process enabled the acquisition of a high photocurrent of 1.5 mA cm−2 vs. RHE 0 V and allowed extremely stable PEC operation for more than one day without using photocatalysts and interlayers. Furthermore, the perfect chemical isolation of the Cu2O nanowires from the electrolyte allows remarkably stable PEC operation with maintenance of the initial photocurrent for more than one day. The synthesis of successful passivation layers via the solution-based process can potentially provide a simple and convenient method for forming various protective films on photoelectrodes with various morphologies and shapes. |
