Designer Titania-Supported Au–Pd Nanoparticles for Efficient Photocatalytic Hydrogen Production

Abstract

Photocatalytic hydrogen evolution may provide one of the solutions to the shift to a sustainable energy society, but the quantum efficiency of the process still needs to be improved. Precise control of the composition and structure of the metal nanoparticle cocatalysts is essential, and we show that fine-tuning the Au-Pd nanoparticle structure modifies the electronic properties of the cocatalyst significantly. Specifically, Pd(shell)-Au(core) nanoparticles immobilized on TiO2 exhibit extremely high quantum efficiencies for H2 production using a wide range of alcohols, implying that chemical byproducts from the biorefinery industry can be used as feedstocks. In addition, the excellent recyclability of our photocatalyst material indicates a high potential in industrial applications. We demonstrate that this particular elemental segregation provides optimal positioning of the unoccupied d-orbital states, which results in an enhanced utilization of the photoexcited electrons in redox reactions. We consider that the enhanced activity observed on TiO2 is generic in nature and can be transferred to other narrow band gap semiconductor supports for visible light photocatalysis.

Solar Hydrogen Generation from Lignocellulose

“…[17] Non-precious co-catalysts (Ni, [15b,18] Fe, [19] Cu) [13a] improved activity [15a] and allowed quantitative H 2 yield. [13b,20] Moreover,heteroatom doping (B/N, [21] S, [22] F) [23] or sensitization with upconverting Er:YAlO 3 particles was employed to improve the light absorption of TiO 2 .…”

Palladium‐Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions

“…[2][3][4][5] Meanwhile, recent years have witnessed a growing interest in palladium (Pd)-based nanomaterials due to their fascinating properties and potential applications in catalysts. [ 1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19] Given that the reactivity and selectivity of a catalyst are highly dependent on specifi c pathways of reactions, it is imperative to decode the mechanism behind each reaction in an effort to achieve rational catalyst design. In particular, oxida-…”

Pd/TiO2-WO3 photocatalysts for hydrogen generation from water-methanol mixtures

“…Some authors have suggested that the reduction of the photogenerated holes may happen when they are transferred directly toward the methanol or by intermediary species such as hydroxyl radicals (•OH) or oxide ions (O 2-), formed from the oxidation of water molecules or by reduction of remaining oxygen molecules (O2) (even after deaeration) that are adsorbed on the photocatalytic surface, or both simultaneously [34]. Other authors proposed that the dissociation of the organic compounds can be complete arriving to CO2 and H2O, or partial, where the reaction proceeds into the dissociation of next intermediary products [38,39]. Patsoura et al [16] explained also that the addition of organic compounds in photocatalytic reactions helps to clean up the catalyst surface from "poisons", which results into a higher hydrogen evolution.…”

“…Table 2 shows a comparison of quantum yield values (%) for hydrogen production obtained by several catalysts based, most of them, on TiO2. Quantum yield (QE or φ ) [10] and Apparent Quantum efficiency (AQE) [39] , [36] It is significant to mention that quantum yield parameter is only an indicative value of the hydrogen evolution per unit of photons incoming to the photocatalytic system; therefore, the comparison based in this parameter does not take into account experimental conditions such as the amount of catalyst, the content of metal or the reaction volume. Table 2 shows different catalysts based on noble metals (Pd or Pt) supported on TiO2.…”