Spatially charge-separated 2D homojunction for photocatalytic hydrogen production

Suppression of photogenerated charge recombination is crucial for efficient photocatalytic hydrogen production.Homojunctions have garnered more attention than heterojunctions due to their superior crystal binding and band structure matching.However,most homojunctions suffer from redox interference caused by continuous oxidizing and reducing phases that impede the ability to improve photocatalytic activity.Consequently,the preparation of homojunction photocatalysts with completely spatial separation of both in charge and redox phases remains challenging.Here,the preparation of a two-dimensional(2D)homojunction CeO_(2) with a back-to-back geometry and fully separated oxidizing and reducing phases is reported.The prepared CeO_(2) is composed of nanosheets with twocontrasting smooth and rough surfaces.Experimental and theoretical results indicate that the rough surface contains more highly reducing CeO_(2){220}and strongly visiblelight-absorbing CeO_(2){200}facets than the smooth surface.The 2D homojunction CeO_(2) produces three-times more hydrogen than normal CeO_(2) nanosheets,and even more than that of CeO_(2) nanosheets loaded with gold nanoparticles.This work presents a new homojunction photocatalyst model with completely spatial separation of both in charge and redox phases that is expected to inspire further research into homojunction photocatalysts.

Preparation and optical properties of tin dioxide inverse opal film

As a novel structure, inverse opal, with threedimensional periodic macropore and mesopore and huge specific surface area, has great promising applications. In this paper, tin dioxide (SnO_(2)) inverse opal films were prepared with sol–gel method by cooperative opal template. The surface morphologies of SnO_(2)inverse opal films were examined by scanning electron microscopy (SEM), the inner structure of SnO_(2)inverse opal films was examined by transmission electron microscopy (TEM), the optical properties of SnO_(2)inverse opal films were studied and discussed in detail. Optical reflectance spectra reveal that, for the opal films, the wavelengths of the reflectance peak confirmed by the experimental reflectance spectra are consistent with the theoretical values;for the SnO_(2)inverse opal films, the wavelengths of the reflectance peak confirmed by the experimental reflectance spectra deviate from theoretical values largely.

Improved photocatalytic performance of acetaldehyde degradation via crystal plane regulation on truncated octahedral CeO_(2)

In this study,the truncated octahedral CeO_(2)(CeO_(2)-to)with special morphology was prepared by the solvothermal method with oleic acid(OA)and oleamine(OM)as the morphology-directing agents.High-resolution transmission electron microscopy(HRTEM)results show that CeO_(2)-to exposes composite{100}and{111}facets,while CeO_(2)cubic(CeO_(2)-c)and CeO_(2)octahedral(CeO_(2)-o)only expose single crystal facets of{100}plane and{111}plane,respectively.Interestingly,this CeO_(2)-to photocatalyst exhibits remarkable photooxidation performance of gaseous acetaldehyde(CH_(3)CHO)degradation,in which CO_(2)generation value reaches 1.78 and 7.97-times greater than that of CeO_(2)-c and CeO_(2)-o,respectively.In addition,the active species trapping experiment signifies that superoxide(·O_(2)^(-))and holes(h^(+))are the main reactive substances during the CH_(3)CHO degradation process,and the electron paramagnetic resonance(EPR)spectra indicates that the former is the major contributor.Notably,the electron transfer mechanism between CeO_(2)-to{100}and{111}facets and the surface oxygen adsorption ability are revealed via density functional theory(DFT)calculations.It is also confirmed that{100}facets are more conducive to the absorption of acetaldehyde than{111}facets.Finally,a reasonable mechanism for improved photocatalytic CH_(3)CHO degradation on CeO_(2)-to is proposed based on relevant experiments and DFT calculations.This study demonstrates that the systematic development of surface homojunction structured photocatalysts can efficiently increase the degradation activity for volatile organic compounds(VOCs).It also offers additional direction for optimizing the photocatalytic activity of other ceriumbased photocatalysts.