| Nowadays,the shortage of fossil energy and environmental pollution have become a serious problem which would restrict the sustainable development of the society.The development of clean renewable energy,such as wind energy,solar energy and tidal energy,can greatly optimize the energy structure of the society.Therefore,many researchers are work on the full utilization and development of solar energy storage and conversion.As an important means of developing solar energy,photocatalysis is a series of chemical reactions driven by the photocatalyst receiving external light radiation.In the photocatalytic process,the photocatalytic material plays a role in promoting the reaction but does not change,which converts the light energy into chemical energy.In order to improve the utilization efficiency of light energy,photocatalytic materials and devices,such as the selection of semiconductor materials,the design of energy band structure and the morphology and structure optimization,need to be studied systematically.At present,many studies have reported that photonic crystal materials show a great application prospect in the field of photocatalysis for their specific properties.By combining the photonic crystal structure characteristics,high efficiency and ideal semiconductor photocatalytic materials can be produced.Three-dimensional ordered porous photonic crystals are characterized by high specific surface area,adjustable hole diameter,total reflection,diffuse reflection and slow photon effect.Firstly,the three-dimensional interconnected ordered porous or mesoporous structure photonic crystals has a high specific surface area,which increases the contact area of reactants and the reactive sites to enhance the photocatalytic activity.Secondly,the photon near the photonic gap has a slow photon effect in the photonic crystal propagation process.The main reason for the great application potential of photonic crystals in the field of solar energy conversion and photocatalysis is the slow photon effect.The slow photon effect can reduce the speed of the photon,which endows the photon a longer lifetime and optical path.Meanwhile,the photon capture efficiency of the photocatalytic material is improved,and the interaction between the photon and the reactant can be enhanced.Finally,the reflection of photonic crystal films on specific wavelengths enables them to reflect the light of a certain frequency to the photocatalyst on the upper layer.The secondary absorption can enhance their light capture ability which would improve the generation rate of photogenic current and enhance the photocatalytic activity.Therefore,photonic crystal materials can be introduced into photocatalysis technology to improve the utilization rate of light and further improve the photocatalytic efficiency.In this paper,photonic crystals are used as structural frames and semiconductor photocatalytic materials to prepare photocatalysts with superior photocatalytic properties.Firstly,we describe the fabrication of photoelectrode derived from ordered photonic crystals SnO2 film,which exhibit photocurrent over 2 times greater than that on planar analogues.Multiple layered ordered photonic crystals SnO2（PCs-SnO2）electrode was homogeneously decorated withα-Fe2O3photocatalyst as a photoanode for solar energy conversion.The as-prepared PCs-SnO2 electrodes were coated withα-Fe2O3 via typical hydrothermal method with varied conditions to manipulate the nanostructure ofα-Fe2O3@PCs-SnO2.The PCs-SnO2 film was applied for four roles:supplying large surface area,reducing recombination,enhancing light absorption and morphology control ofα-Fe2O3,among which the role for morphology control was particularly studied.In comparison to planar analogue,the size ofα-Fe2O3 was contained to a certain scale even after post heat treatment.In addition,to further investigate the PCs-SnO2 applications on morphology control,PCs-Zn O and PCs-Si O2 films were also fabricated as control groups.Secondly,we report the direct synthesis of WO3 using PCs-FTO substrates from WCl6precursor solution via wet chemistry approach without adding of any surface reagent,and the WO3 was homogeneously grown on the skeleton of PCs-FTO substrates to form WO3@PCs-FTO.Using PCs as substrates for photoactive materials,utilization of light was improved because of the incident light manipulation.In addition,the photonic crystal substrate was exploited for controlling the crystal morphology of WO3 and also improving the light harvesting under different incidences.It is found that in 15 to 45 incidence range,the PCs substrate exhibits remarkable optimization of PEC efficiency for the WO3,in comparison to p-FTO.Since the sun can be considered as a changing incidence light source in practical applications,the PCs substrate revealed significant value for solar energy conversion systems.Finally,Z-scheme structured photocatalytic material is a new type of semiconductor heterojunction structure,which is combined with two kinds of semiconductor materials with suitable band gap.The photogenerated electrons in the lower conduction band of one semiconductor can be rapidly transferred to the valence band of another semiconductor,and finally recombined with the holes in the valence band.Therefore,Z-scheme photocatalytic compound has a higher redox potential and can effectively improve the utilization of photogenerated carriers.WO3@PCs-FTO synthesized via a solvothermal method,and WO3-CdS@PCs-FTO synthesized by in-situ method.Benefited to the direct Z-scheme heterostructure of WO3-CdS,photo-generated electrons and holes have been separated effectively,it was found that WO3-CdS@PCs-FTO showed largely improved photocatalyst activity comparing with WO3@PCs-FTO.Moreover,photonic crystal FTO has been used in the photoanode because of its inverse opal structure,which can enhance light absorption.This work has provided a potential way to improving the efficiency of photocatalytic performance of photocatalyst and optimizing the utilization of sunlight in the field of solar energy and solar cell. |
