Recent progress on doped ZnO nanostructures for visible-light photocatalysis

Abstract

Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures have played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light.

The Applications of Morphology Controlled ZnO in Catalysis

“…ZnO basted catalysis has attracted much attention and presents a rising interest as displayed above and surveyed by Samadi et al [81]. As reviewed in Sections 2-4, morphology control strategy is a good approach to modify the catalytic activity of ZnO nanostructures for many reactions in both environmental and energy fields.…”

“…Although there is abundant published work on doped ZnO nanostructures [80,81,258], large scale synthesis methods of doped ZnO particularly nonmetal doped ZnO with reguar morphologies should be further developed, which will enable its wide applications in catalysis. ii.…”

Property of Zinc Oxide (Zno) Nanostructures Potential for Biomedical System and Its Common Growth Mechanism

“…It is well known that ZnO has a wide band gap (3.37eV) compound semiconductor attractively suitable for short wavelength optoelectronic applications [1,2] and its high exciton binding energy (60meV) ensure efficient excitonic emission at room temperature, which already has been reported in published literature with disordered nanoparticles and thin films [3,4]. Also, ZnO is transparent to visible light and can be made highly conductive by doping [5][6][7]. Moreover, due to its unique characteristics of crystal structure, the lack of a symmetry center in wurtzite structure and large electromechanical coupling result in strong piezoelectric and pyroelectric properties and show predominant applications in mechanical actuators and piezoelectric sensors [8][9][10], chemical sensors [11,12] and solar cells [13,14].…”

Influenza of the Cu Ion on the Structural and Optical Properties in Cu + Ce Co-Doped ZnO Compounds

“…The second two peaks are centered in the redcolor region, and are due to a radiative recombination process that occurs between the donors associated with oxygen vacancies O v and the acceptors associated with the native defects adjacent to the Cu 2+ impurity [32]. It is important to note from Figure 4 that the UV PL was quenching of the PL spectra; this quenching effect is caused by a non-radiative recombination process known as non-radiative Auger recombination phenomena [33] associated to degenerate electrons, in which the energy released by an electron is immediately recombined and absorbed by another electron and the energy involved is dissiped by phonons [21], and [22]. Auger process is considered as the cause major of non-radiative recombination in semiconductor materials.…”