Selective Oxidation of Benzyl Alcohol by Ag/Pd/m-BiVO4 Microspheres under Visible Light Irradiation

Abstract

A series of Ag/Pd/m-BiVO4 (monoclinic) bimetallic photocatalytic materials with different loading amounts and different mass ratios of Ag and Pd were synthesized by a hydrothermal method and an NaBH4 reduction method. The Ag/Pd/m-BiVO4 photocatalyst with a total Ag and Pd loading of 2 wt% and an Ag-to-Pd mass ratio of 2:1 can selectively oxidize benzyl alcohol to benzaldehyde under visible light irradiation, the conversion rate was up to 89.9%, and the selectivity was greater than 99%. The conversion rate on Ag/Pd/m-BiVO4 was higher than those on Ag/m-BiVO4 and Pd/m-BiVO4. The photocatalysts were characterized by X-ray powder diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, N2 adsorption-desorption isothermal curves (BET) and other means. The effects of different light wavelengths and light intensities were compared. Then, the effects of different alcohol derivatives on the reactions were explored. The cycle experiments proved that the Ag/Pd/m-BiVO4 photocatalyst had good light stability and thermal stability. In addition, the capturing experiment of active species shows that the selective oxidation of benzyl alcohol is mainly accomplished through the synergistic action of h+, e−, •OH and •O2−.

Bismuth‐Based Oxide Photocatalysts for Selective Oxidation Transformations of Organic Compounds

“…[97] Plasmonic metals, including Pd, Ru, Ag and Au, have been incorporated into BiVO 4 in catalytic reactions. [107][108][109][110] BiVO 4 decoration with Pd and Au resulted in a 6-fold increased yield for the oxidation of aromatic alcohols toward benzaldehyde compared to BiVO 4 alone. [108] From ESR and scavenger experiments, a carbon centered radical, h + and * O 2 À were identified as the main reactive species during these photoreactions.…”

“…Plasmonic metals, including Pd, Ru, Ag and Au, have been incorporated into BiVO 4 in catalytic reactions [107–110] . BiVO 4 decoration with Pd and Au resulted in a 6‐fold increased yield for the oxidation of aromatic alcohols toward benzaldehyde compared to BiVO 4 alone [108] .…”

Nanomaterials in Photo (Electro) Catalysis

“…A series of Ag/Pd/m-BiVO 4 (monoclinic) bimetallic nano-microspheres with photocatalytic properties are reported in the paper of Yu et al The photocatalysts, prepared by a two-step method (hydrothermal synthesis and chemical reduction) have been characterized by several techniques, and their photocatalytic activity has been investigated in the oxidation of benzyl alcohol under visible light irradiation, in several organic solvents. Optimal conditions for the preparation of the nano-microspheres allow to produce a photocatalyst able to achieve a conversion rate up to 89.9% and a selectivity greater than 99% under suitable experimental conditions [14].…”

Nanoscale Assembly of CdS/BiVO4 Hybrids for Coupling Selective Fine Chemical Synthesis and Hydrogen Production under Visible Light

“…As the simplest aromatic aldehyde with an active carbonyl group, benzaldehyde (BAD) occupies an essential position in organic reaction intermediates. , The traditional industrial way to synthesize BAD is liquid toluene oxidation or benzoyl chloride hydrolysis, which not only generates various byproducts (bromobenzene, etc. ), but also brings about severe environmental pollution and energy waste. , In this context, solar-driven oxidation of benzyl alcohol (BA) has attracted more attention due to its advantages of benign environmental impact and low energy consumption. − Most of the various researches on photocatalytic alcohols oxidation choose oxygen (O 2 ) as the electron acceptor. ,, In comparison, direct splitting of alcohols into hydrogen (H 2 ) and corresponding carbonyl products not only makes full use of the energy of photoinduced electron–hole pairs, but also produces clean H 2 fuels, thereby offering a cooperative photoredox reaction system. , Accordingly, photocatalytic selective conversion of BA at ambient conditions coupling with protons reduction to produce H 2 is a promising alternative. − …”

“…Some strategies have been developed to overcome the aforementioned shortcomings, such as morphological control, loading cocatalysts, doping impurity, and designing type-II heterostructure composites. These methods can improve the shortcomings of low photogenerated carriers transport and separation efficiency, but cannot change the fact that the energy of the photogenerated electrons is not sufficient to reduce hydrogen protons. ,− In comparison, designing composite materials with a Z-scheme charge transfer pathway is a feasible solution to achieve this goal for the photoexcited electrons and holes gathering in a more negative CB and a more positive VB, respectively, thereby retaining strong photoredox properties. ,,− …”