Photocatalytic Oxidation of 5‐Hydroxymethylfurfural Over Interfacial‐Enhanced Ag/TiO₂ Under Visible Light Irradiation

Abstract

Photocatalytic conversion of biomass-derived 5-hydroxyfurfural (HMF) to value-added 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) is an environmentally friendly process. Here, Ag nanoparticle (NP) supported on TiO 2 (Ag/TiO 2 ) materials with different interfacial structures were fabricated via incipient wetness impregnation. In the photocatalytic oxidation of 5-HMF to HMFCA, low-temperature reduction (473 K) on Ag/TiO 2 could improve the photoinduced charge separation efficiency and promote the reaction due to the "enhanced" localized surface plasmon resonance (LSPR) effects achieved through strong metal-support interaction (SMSI). In particular, 2.5 % Ag/TiO 2 -LTR exhibited superior performance with an HMFCA selectivity of up to 96.7 % under visible-light illumination. In contrast, the photocatalytic efficiency was greatly reduced when the reduction temperature increased to 773 K because of the encapsulation of Ag NPs by a thicker TiO x overlay, which significantly weakened visible-light harvesting. Overall, these findings offer an efficient methodology for designing interfacial enhanced plasmonic photocatalysts for the valorization of biomass.

Control of selectivity in organic synthesis via heterogeneous photocatalysis under visible light

“…As shown in Table 1, the use of holes or superoxide anions (O2 •− ) can drive the selective oxidation of HMF to DFF, HFCA or FFCA (selectivity over 85%) via different photocatalytic systems under visible light irradiation [90][91][92][93][94][95][96][97][98][99]. Several photocatalysts such as Fe(III)/Bi2MoO6, plasmonic Au/TiO2 and g-C3N4/NaNbO3 composite have been developed to generate the mild oxidative species.…”

Visible-Light-Driven Photocatalytic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over Plasmonic Au/ZnO Catalyst

“…Moreover, plasmonic metal nanoparticles (NPs), such as Au, Ag, and Cu, have gained more and more interest due to the LSPR effect. 3 Au is an excellent visible-light-responding photocatalyst. 17 When Au NPs are combined with ZnO, their LSPR effect can increase the absorption of the material in the visible region and improve the utilization efficiency of light.…”

“…The peaks of O 1s can be deconvoluted into three subpeaks at ∼530.8, ∼531.7, and ∼533.1, corresponding to the Zn−O bond, oxygen vacancy on the ZnO support, and water molecules adsorbed on the catalyst surface or surface-adsorbed oxygen species, respec- tively. 3 The deconvolution of the oxygen vacancy in the O 1s spectra of 2.5% Au/ZnO DP-N , 2.5% Au/ZnO DP-air , and 2.5% Au/ZnO DP-H gives the relative percentages of oxygen vacancy, which are 31.1, 30.9, and 35.3%. The results showed that the oxygen vacancy concentration of ZnO treated with air is the lowest, while calcination in N 2 can slightly increase the oxygen vacancy concentration, and H 2 treatment introduced the highest concentration of oxygen vacancy.…”

“…PL spectroscopy was used to study the photophysical properties of electron−hole pairs such as the nature of the defects and the recombination and transfer kinetics of light-induced charge carriers. 3 Figure 5A presents the PL intensity of the catalysts with the excitation wavelength of 330 nm. It is obvious that the intensity of all Au/ZnO catalysts is much lower than that of pristine ZnO, which indicates that the loading of Au NPs can effectively inhibit the recombination of photogenerated electron−hole pairs.…”

“…This may be due to the formation of the Schottky barrier at the interface between Au and ZnO, which prevents the recombination of electron−hole pairs. 3 Furthermore, the oxygen vacancy on ZnO support may also play a role in capturing electrons and preventing recombination. 21 Transient Photocurrent Response and EIS.…”