Hierarchical tree-like heterostructure arrays for enhanced photoeletrochemical activity.

The structure of biomimetic approach to converting sunlight was applied for design of composite materials. Here, hierarchical tree-like heterostructure Ag/ZnO (Ag wt%: 8.9%) arrays were fabricated by two-step electrodeposition, and it exhibited improved activity during photoelectrochemical water oxidation. The wurtzite-structured ZnO arrays prepared are the "trunk". Ag nanoclusters were selectively deposited on the top of arrays as the "leaf", which can strongly interact with visible light due to surface plasmon resonance. The inducted electromagnetic fields around Ag would efficiently propagate energy to composites by hot electrons injection. Based on morphology and crystal structure analysis, the linear sweep voltammagrams display that photocurrent increase to 0.17mA/cm2 at 1.23 VRHE, and the photo-to-hydrogen generation is 0.23%. Additionally, the amperometric I-t curves collected without voltage displayed better photocurrent response under sunlight. The kinetics of PEC process at the electrode surface was investigated by electrochemical impedance spectroscopy (EIS). The mechanism was deduced based on the energy level of ZnO and Ag. The designed plasmonic crystal system exhibited that tree-like heterostructure is favorable for improving sunlight absorption and photoeletrochemical performance. [ABSTRACT FROM AUTHOR]