偏压控制Cu2O和Cu在TiO2表面的生长及其光电化学性质

基于TiO2/Ti电极在含Cu2+溶液中的循环伏安图,调节电沉积的沉积电压,我们在TiO2平整表面制备出Cu2O和/或Cu颗粒.通过扫描电镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)表征,发现Cu2O和Cu有不同的生长机制:Cu2O颗粒在TiO2表面分散结晶,而Cu颗粒是在已生长的颗粒上成核,从而形成堆积颗粒结构.这是由于在Cu2O/TiO2界面和Cu/TiO2界面形成不同的能带结构,使得电子的转移方式不同.与纯TiO2光阳极比较,可以观察到Cu2O/TiO2和Cu/TiO2异质结构的光电流均有显著增强.特别地,存在一个电压区间使得Cu2O和Cu同时生长在TiO2表面,此时对应的光电流比较稳定并且能达到最大.紫外-可见(UV-Vis)漫反射光谱、电化学阻抗谱(EIS)和光电流-电压特性曲线均显示,Cu2O和Cu明显有助于光的可见光吸收,同时Cu/TiO2在光电转换过程中显示更宽波段的可见光利用率.此外,开路电压的增加、有效的电荷分离和电极/电解质界面上载流子的快速迁移也增强了材料的光电化学性质.

Bias-Determined Cu2O and Cu Growth on TiO2 Surface and Their Photoelectrochemical Properties

Based on the cyclic voltammogram (CV) of TiO₂/Ti electrodes in Cu²⁺ ion solution, we fabricated Cu₂O and Cu particles onto TiO₂ flat surfaces separately or simultaneously by adjusting the applied potentials during electrodeposition. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that Cu₂O and Cu have different growth modes: Cu₂O particles crystallize on the TiO₂ surface separately while Cu particles nucleate on previously grown particles, forming a stacked particle structure. This growth behavior can be explained by the different electron transfer behavior on the Cu₂O/TiO₂ and Cu/TiO₂ interfaces and this is determined by their bandgap alignments. Compared with a pure TiO₂ photoanode, a significant enhancement of the photocurrent was observed for both the Cu₂O/TiO₂ and Cu/TiO₂ heterostructures. A potential region exists where Cu₂O and Cu grow on the TiO₂ surface simultaneously and the corresponding photocurrent is relatively stable and reaches a maximum. UV-Vis diffuse reflectance spectroscopy, electrochemical impedance spectroscopy (EIS), and photocurrent vs potential characteristics revealed that the visible light absorption by Cu₂O and Cu contributes significantly to the photocurrent. Cu/TiO₂ resulted in greater broadband visible light utilization during the photoelectric conversion. Additionally, the increased zero-current potential and the effective charge separation as well as the rapid carrier transfer on the electrode/electrolyte interface are also related to the enhanced photoelectrochemical properties.