Synthesis of palladium-decorated defective tungsten oxide heterostructures with enhanced photothermal catalytic activity for hydrodeoxygenation of vanillin

Abstract

The selective hydrodeoxygenation (HDO) of sustainable lignocellulosic biomass plays a pivotal role in the conversion of biomass into high-value fuels and chemicals. Nevertheless, HDO for biomass upgrading always demands high temperatures and high hydrogen (H2) pressure. Photothermal catalysis has been recognized as an effective approach for boosting chemical reactions under mild conditions while maintaining superior selectivity. Herein, we report the design of palladium-decorated defective tungsten oxide (Pd/WO3-x) catalysts with enhanced photothermal catalytic performances for the efficient HDO of vanillin. Pd/WO3-x nanoflowers have been synthesized through a solvothermal/in-situ reduction two-step strategy, and they exhibit notable photoabsorption in a wide range (200–1100 nm), high photothermal conversion and efficient charge separation efficiency. Under simulated sunlight irradiation (0.3 W cm−2), Pd/WO3-x exhibits a maximum vanillin conversion up to 86.8 % with a 2-methoxy-4-methylphenol (MMP) selectivity of 100 %, which is obviously higher than that (vanillin conversion = 33.1 %, MMP selectivity = 100 %) in the oil bath at the same temperature. Such higher conversion efficiency and selectivity under sunlight should result from the synergistic integration of hot electrons and photothermal heating, both of which are derived from localized surface plasmon resonance (LSPR) in WO3-x. Importantly, Pd/WO3-x catalyst demonstrates good stability and high selectivity to MMP even after 5 cycles. This work may offer a novel viewpoint on the advancement of photothermal catalysts and the realization of photothermal catalytic biomass conversion under mild conditions.