Lanqin Tang

Rational construction of a CdS/reduced graphene oxide/TiO2 core–shell nanostructure as an all-solid-state Z-scheme system for CO2 photoreduction into solar fuels

Mimicking natural photosynthesis in green plants, an all-solid-state Z-scheme was constructed for photocatalytic reduction of CO2 in the presence of water vapor, consisting of CdS nanospheres (CdS NSs) and TiO2 nanoparticles as photocatalysts, and reduced graphene oxide (rGO) as a solid electron mediator. In this Z-scheme system, the photogenerated electrons from the conduction band of TiO2 transfer to rGO, and then recombine with the existing holes of CdS NSs, allowing the photo-generated electrons to enrich on the CdS semiconductor and holes on the TiO2. The photocatalytic efficiency of the Z-scheme system exhibits remarkable enhancement relative to pure CdS, CdS/TiO2, and CdS/rGO.

Construction of an all-solid-state artificial Z-scheme system consisting of Bi2WO6/Au/CdS nanostructure for photocatalytic CO2 reduction into renewable hydrocarbon fuel

An all-solid-state Bi2WO6/Au/CdS Z-scheme system was constructed for the photocatalytic reduction of CO2 into methane in the presence of water vapor. This Z-scheme consists of ultrathin Bi2WO6 nanoplates and CdS nanoparticles as photocatalysts, and a Au nanoparticle as a solid electron mediator offering a high speed charge transfer channel and leading to more efficient spatial separation of electron-hole pairs. The photo-generated electrons from the conduction band (CB) of Bi2WO6 transfer to the Au, and then release to the valence band (VB) of CdS to recombine with the holes of CdS. It allows the electrons remaining in the CB of CdS and holes in the VB of Bi2WO6 to possess strong reduction and oxidation powers, respectively, leading the Bi2WO6/Au/CdS to exhibit high photocatalytic reduction of CO2, relative to bare Bi2WO6, Bi2WO6/Au, and Bi2WO6/CdS. The depressed hole density on CdS also enhances the stability of the CdS against photocorrosion.

Bi2MoO6 Nanostrip Networks for Enhanced Visible-Light Photocatalytic Reduction of CO2 to CH4

A three-dimensional Bi2 MoO6 nanostrip architecture was synthesized by the hydrothermal method using sodium oleate as a surfactant. The generated Bi2 MoO6 nanostrips intercross with each other to form a unique network structure with a band gap of 2.92 eV, corresponding to visible-light wavelength. Time-evolution experiments reveal the formation mechanism of the Bi2 MoO6 network. The photocatalytic reduction of CO2 to CH4 catalyzed by the Bi2 MoO6 architecture was evaluated and compared with the process catalyzed by a Bi2 MoO6 nanoplate analogue synthesized in the absence of sodium oleate as well as with the solid-state reaction. The Bi2 MoO6 nanostrips exhibit the best photocatalytic activity, which can be attributed to their high specific surface area, high light-absorption intensity, suitable thickness for fast charge-carrier migration, and the presence of pores for reactant transport.

Series of ZnSn(OH)6 Polyhedra: Enhanced CO2 Dissociation Activation and Crystal Facet-Based Homojunction Boosting Solar Fuel Synthesis

A series of ZnSn(OH)6 polyhedra are successfully explored with well-controlled area ratio of the exposed {100} and {111} facets. Band alignment of the exposed facet-based homojunction of the elegant polyhedron facilitates spatial separation of photogenerated electrons and holes on {111} and {100} surfaces, respectively. Optimal area ratio of {100} to {111} is the prerequisite for pronounced CO2 photocatalytic performance of high-symmetry cuboctahedra into methane (CH4). The synergistic effect of the excess electron accumulation and simultaneously the enhanced CO2 absorption and low dissociation activation energy on {111} reduction sites promote the yield of CO2 photocatalytic conversion product.

TiO2 nanosheet-anchoring Au nanoplates: high-energy facet and wide spectra surface plasmon-promoting photocatalytic efficiency and selectivity for CO2 reduction

An Au–TiO2 nanocomposite consisting of (001) exposed TiO2 nanosheet-anchored Au nanoplates was successfully fabricated using bifunctional linker molecules and applied for the photocatalytic reduction of CO2 into hydrocarbon fuels. This unique nanocomposite benefits from the combination of the higher photocatalytic activity of TiO2 (001) and the visible to near-infrared region plasma resonances of anisotropic Au nanostructures. Several carbon fuels were selectively produced over the Au–TiO2 nanocomposite, including CO, CH4, CH3OH and CH3CH2OH, under different forms of light irradiation and in different reaction systems. Both photoresponse testing and electrochemical impedance spectroscopy measurements confirm the importance of the Au surface plasmon for the photocatalytic activity.

Quasi-Topotactic Transformation of FeOOH Nanorods to Robust Fe2O3 Porous Nanopillars Triggered with a Facile Rapid Dehydration Strategy for Efficient Photoelectrochemical Water Splitting

A facile rapid dehydration (RD) strategy is explored for quasi-topotactic transformation of FeOOH nanorods to robust Fe2O3 porous nanopillars, avoiding collapse, shrink, and coalescence, and compared with a conventional treatment route. Additionally, the so-called RD process is capable of generating a beneficial porous structure for photoelectrochemical water oxidation. The obtained RD-Fe2O3 photoanode exhibits a photocurrent density as high as 2.0 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE) and a saturated photocurrent density of 3.5 mA cm-2 at 1.71 V versus RHE without any cocatalysts, which is about 270% improved photocurrent density over Fe2O3 with the conventional temperature-rising route (0.75 mA cm-2 at 1.23 V vs RHE and 1.48 mA cm-2 at 1.71 V vs RHE, respectively). The enhanced photocurrent on RD-Fe2O3 is attributed to a synergistic effect of the following factors: (i) preservation of single crystalline nanopillars decreases the charge-carrier recombination; (ii) formation of long nanopillars enhances light harvesting; and (iii) the porous structure shortens the hole transport distance from the bulk material to the electrode-electrolyte interface.

Synthesis of single-crystalline, porous TaON microspheres toward visible-light photocatalytic conversion of CO2 into liquid hydrocarbon fuels

Single-crystalline, porous TaON microspheres were prepared for photocatalysis via facile nitridation of uniform amorphous Ta2O5 sphere formed by hydrothermal treatment. The amorphous property facilitates shrinkage of Ta2O5 into the porous TaON nanostructure during the ammonification process. The porous spherical architecture of TaON plays a significant role in deciding the CO2 photocatalytic conversion efficiency into ethanal and ethanol under visible light irradiation, relative to its counterpart from commercial Ta2O5, including availability of more reaction sites, easy trapping of incident illumination, and shortening of charge transfer distance from the interior to the outer surface to expedite charge separation. Loading Pt as an electron sinker over the porous TaON, boosting the separation of the photogenerated electron–hole pairs, not only improves the photoconversion efficiency, but also alters the product species.