ZIF-8 derived bimodal carbon modified ZnO photocatalysts with enhanced photocatalytic CO₂ reduction performance

Abstract

The use of ZnO photocatalysts is usually limited by their low specific surface area, low visible light absorption capacity and inferior photochemical stability. In this report, visible-light responsive porous ZnO photocatalysts were fabricated by calcining pre-synthesized ZIF-8 (a kind of zeolitic imidazolate framework) polyhedra as solid precursor in air at suitable calcination temperature. It was showed that the crystallographic structure of ZIF-8 precursor was basically remained up to 300 C upon calcination, while phase transformation from ZIF-8 to wurtzite ZnO nanocrystals progressively proceeded above 400 C. Interestingly, special bimodal carbon modifications, that is, simultaneous carbon doping and surface carbon coating, were achieved simultaneously during pyrolysis, which were confirmed by X-ray photoelectron spectroscopy, Fourier transform Raman spectroscopy and electron microscopy. The nitrogen sorption analysis indicated that the high specific surface area and mesoporous texture was partially inherited from highly porous ZIF-8. As a consequence of cooperative textural and carbon modifications, the as-prepared mesoporous ZnO photocatalyst was efficient in both CO 2 capture and photocatalytic CO 2 reduction towards CH 3 OH as a typical solar fuel under full-spectrum Xe lamp irradiation. Especially, the 500 C-calcined sample manifested the highest photocatalytic CO 2 reduction activity (0.83 mmol h À1 g À1 ), which was about six folds higher than that of hydrothermally synthesized ZnO nanorods as reference. Specifically, the superior photocatalytic CO 2 reduction performance was associated with the bimodal carbon modification, high specific surface area and porous framework, which contributed to enhanced visible light harvesting, charge transport and CO 2 capture.

MOF‐Based Transparent Passivation Layer Modified ZnO Nanorod Arrays for Enhanced Photo‐Electrochemical Water Splitting

“…The bands at 1146 and 1180 cm −1 are related to CN stretching, and 833, 950, and 1020 cm −1 are assigned to CH bending, from the ZIF‐8 overlayer . The presence of abundant surface defects in ZnO/NF results in the broad Raman peak centered at about 1112 cm −1 . In contrast, after the ZIF‐8 modification, this peak disappears, implying the in situ ZIF‐8 coating decreases the surface defects of ZnO NRARs.…”

Hollow Au‐ZnO/CN Nanocages Derived from ZIF‐8 for Efficient Visible‐Light‐Driven Hydrogen Evolution from Formaldehyde Alkaline Solution

“…In this study, UV/Vis diffuse‐reflectance spectroscopy was used (Figure a) to examine the optical characteristics. The spectra shows that ZnO exhibits its characteristic strong absorption in the UV range while ZnO/CN and Au 0.08 ‐ZnO/CN display a visible‐light absorption, which is likely caused by incomplete combustion of organic species according to the TG results in Figure S7 . As the degree of etching increases, the Au SPR effect is greatly enhanced.…”

Carbon‐Modified CuO/ZnO Catalyst with High Oxygen Vacancy for CO2 Hydrogenation to Methanol

“…Graphene oxide improves the reducibility of Cu active component, the adsorption capacity of H 2 and CO 2 , and the catalytic activity . ZnO, with carbon modification derived from zeolite imidazolate framework‐8 (ZIF‐8), is active for CO 2 capture and photocatalytic CO 2 reduction to methanol …”