title: ZnO/CuO heterojunction branched nanowires for photoelectrochemical hydrogen generation.
abstract: We report a facile and large-scale fabrication of three-dimensional (3D) ZnO/CuO heterojunction branched nanowires (b-NWs) and their application as photocathodes for photoelectrochemical (PEC) solar hydrogen production in a neutral medium. Using simple, cost-effective thermal oxidation and hydrothermal growth methods, ZnO/CuO b-NWs are grown on copper film or mesh substrates with various ZnO and CuO NWs sizes and densities. The ZnO/CuO b-NWs are characterized in detail using high-resolution scanning and transmission electron microscopies exhibiting single-crystalline defect-free b-NWs with smooth and clean surfaces. The correlation between electrode currents and different NWs sizes and densities are studied in which b-NWs with longer and denser CuO NW cores show higher photocathodic current due to enhanced reaction surface area. The ZnO/CuO b-NW photoelectrodes exhibit broadband photoresponse from UV to near IR region, and higher photocathodic current than the ZnO-coated CuO (core/shell) NWs due to improved surface area and enhanced gas evolution. Significant improvement in the photocathodic current is observed when ZnO/CuO b-NWs are grown on copper mesh compared to copper film. The achieved results offer very useful guidelines in designing b-NWs mesh photoelectrodes for high-efficiency, low-cost, and flexible PEC cells using cheap, earth-abundant materials for clean solar hydrogen generation at large scales.
authors.affiliation: Department of Electrical and Computer Engineering, University of California-San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.
authors.forename: Alireza
authors.initials: A
authors.lastname: Kargar
authors.forename: Yi
authors.initials: Y
authors.lastname: Jing
authors.forename: Sung Joo
authors.initials: SJ
authors.lastname: Kim
authors.forename: Conor T
authors.initials: CT
authors.lastname: Riley
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Pan
authors.forename: Deli
authors.initials: D
authors.lastname: Wang