Photoelectrochemical Study of Nanostructured ZnO Thin Films for Hydrogen Generation from Water Splitting

Abstract

Photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting. The ZnO thin films are fabricated using three different deposition geometries: normal pulsed laser deposition, pulsed laser oblique‐angle deposition, and electron‐beam glancing‐angle deposition. The nanostructured films are characterized by scanning electron microscopy, X‐ray diffraction, UV‐vis spectroscopy and photoelectrochemical techniques. Normal pulsed laser deposition produces dense thin films with ca. 200 nm grain sizes, while oblique‐angle deposition produces nanoplatelets with a fishscale morphology and individual features measuring ca. 900 by 450 nm on average. In contrast, glancing‐angle deposition generates a highly porous, interconnected network of spherical nanoparticles of 15–40 nm diameter. Mott‐Schottky plots show the flat band potential of pulsed laser deposition, oblique‐angle deposition, and glancing‐angle deposition samples to be −0.29, −0.28 and +0.20 V, respectively. Generation of photocurrent is observed at anodic potentials and no limiting photocurrents were observed with applied potentials up to 1.3 V for all photoelectrochemical cells. The effective photon‐to‐hydrogen efficiency is found to be 0.1%, 0.2% and 0.6% for pulsed laser deposition, oblique‐angle deposition and glancing‐angle deposition samples, respectively. The photoelectrochemical properties of the three types of films are understood to be a function of porosity, crystal defect concentration, charge transport properties and space charge layer characteristics.

Combining the lotus leaf effect with artificial photosynthesis: regeneration of underwater superhydrophobicity of hierarchical ZnO/Si surfaces by solar water splitting

“…37 In recent years, water-splitting technologies for hydrogen gas generation have been explored globally to develop future alternative energy sources. 38,39 This study presents the first attempt to combine two biomimetic properties of natural leaves, the lotus leaf effect (superhydrophobicity) and artificial leaf effect (photosynthesis), and aims to use hydrogen gas generated by solar water splitting to restore a continuous gas interlayer on submerged superhydrophobic surfaces (Scheme 1). A crucial factor for realizing this objective is to fabricate photocatalytic nanomaterials with low surface energies that act as both the micro-/nano-sized hierarchical papillae in lotus leaves and the photoelectrode for photosynthetic hydrogen generation in artificial leaves.…”

A Review on the Fabrication of Hierarchical ZnO Nanostructures for Photocatalysis Application

“…ZnO has received much attention in many fields of photocatalysis application, such as the degradation and environmental pollutants and H2 generation, owing to its lower cost, non-toxic and efficient photoelectrocatalytic performance [115][116][117][118][119][120][121][122]. Since ZnO (3.37 eV) has almost the same band gap energy as TiO2 (3.2 eV), its photocatalytic capability is anticipated to be similar to that of TiO2.…”

Effect of Surfactant on Growth of ZnO Nanodumbbells and Their Characterization

“…ZnO has a wide direct-band gap of 3.37 eV and high-exciton-binding energy of 60 mV at room temperature. ZnO has been extensively studied because of its fascinating wide range of applications such as chemical sensors and biosensors, piezoelectricity, optoelectronics, photocatalysis, and photoelectrochemical water splitting [1][2][3][4][5][6][7][8]. In many of the applications, ZnO functional properties are highly affected by the morphology of the nanostructure.…”