Photoelectrochemical performance of N-doped ZnO branched nanowire photoanodes

Abstract

A ZnO branched-nanowire (BNW) photoanode was doped with N for use in a photoelectrochemical cell (PEC) to generate H2 from water splitting. First, ZnO BNWs were synthesized by chemical bath deposition method. Two experimental methods were used for N-doping: the time-controlled direct-current glow discharge plasma (DCGDP) and the DC magnetron plasma (DCMP) methods, to optimize N-doping of the NW structure. X-ray photoelectron spectroscopy (XPS) provided the N distribution and atomic percentage in the BNWs. The XPS results confirmed that N distribution into ZnO BNWs occurred by N substitution of O sites in the ZnO structure and through well-screened molecular N2. The morphologies and structures of the fabricated nanostructures were investigated by field-emission scanning electron microscopy and X-ray diffraction respectively. The photoanode performance was demonstrated in photoelectrochemical studies at various power densities under both dark and illuminated conditions. Increasing the N amount in the ZnO BNWs increased the photocurrent in the PEC.

Nitrogen plasma treatment of ZnO and TiO2 nanowire arrays for polymer photovoltaic applications

“…Moreover, it was found that the chemical states and bonding energies of these vibrational states differ according to the plasma treatment type. In any ionizing environment, dissociation and recombination of the plasma species occur simultaneously, with the process that becomes prevalent depending on the plasma power [31]. This is particularly true in this study, as the high power radiofrequency plasma employed produces all three prevalent nitrogen species, namely α-N 2, γ-N 2 and atomic nitrogen.…”

“…In the case of nitrogen plasma treated ZnO, Allami et al [31] reported the use of 100 W direct-current magnetron plasma and 450 V direct-current glow discharge plasma at different exposure periods of ZnO NWs and found that N incorporated in the ZnO lattice structure with multiple chemical states, including the well-screened molecular state (α-N 2 ), molecular nitrogen (γ-N 2 ) and α-N atoms occupying O sites to form Zn 3 N 2 bonds. These results are in agreement with that reported by Tabet et al [32], who added that ZnO 1−x N x forms by the decomposition of Zn 3 N 2 and the re-arrangement of N atoms in the ZnO lattice [32] and NO 2 − on the surface of ZnO thin films irradiated with nitrogen species during DC magnetron sputtering at low kV .…”

pH dependent ZnO nanostructures synthesized by hydrothermal approach and surface sensitivity of their photoelectrochemical behavior

“…Photocatalytic properties of ZnO are of great interest and consequently they have been extensively studied. Especially, photocatalytic water splitting for hydrogen generation is one of the most important applications in the photocatalysis field [9][10][11][12][13][14]. The ZnO properties are often compared with those of TiO 2 due to similarity in bandgap and band edge positions.…”

Current progress in developing metal oxide nanoarrays-based photoanodes for photoelectrochemical water splitting

“…The significant increase of photoresponse in the visible region well accounted for the PEC performance enhancement. Such successful doping strategy has attracted much attention, which resulted in a lots of researches on doped-ZnO NW arrays for PEC application, such as ZnO:N [333,334], ZnO:S [335], ZnO:B [336], ZnO:Co [337], ZnO:Ni [337], ZnO:K [337], ZnO:Na [337,338], ZnO: (Co, N) [339], ZnO: (Al, Cu) [340].…”