Optimised photocatalytic hydrogen production using core–shell AuPd promoters with controlled shell thickness

Abstract

The development of efficient photocatalytic routines for producing hydrogen is of great importance as society moves away from energy sources derived from fossil fuels. Recent studies have identified that the addition of metal nanoparticles to TiO2 greatly enhances the photocatalytic performance of these materials towards the reforming of alcohols for hydrogen production. The core-shell structured Au-Pd bimetallic nanoparticle supported on TiO2 has being of interest as it exhibited extremely high quantum efficiencies for hydrogen production. However, the effect of shell composition and thickness on photocatalytic performance remains unclear. Here we report the synthesis of core-shell structured AuPd NPs with the controlled deposition of one and two monolayers (ML) equivalent of Pd onto Au NPs by colloidal and photodeposition methods. We have determined the shell composition and thickness of the nanoparticles by a combination of X-ray absorption fine structure and X-ray photoelectron spectroscopy. Photocatalytic ethanol reforming showed that the core-shell structured Au-Pd promoters supported on TiO2 exhibit enhanced activity compared to that of monometallic Au and Pd as promoters, whilst the core-shell Au-Pd promoters containing one ML equivalent Pd provide the optimum reactivity.

Measurable surface d charge of Pd as a descriptor for the selective hydrogenation activity of quinoline

“…Third, the 1s → 4f (f) transition shifts to a lower energy and its intensity is significantly reduced. This shift can be interpreted as due to an increase in the atomic separation and the 4d-5p hybridization that has been observed for the local distortion of the Pd lattice by interstitial C [58] and AuPd bimetallic nanoparticles [59]. A further decrease in Pd concentration to 50% (Au50Pd50) leads to no further shift, implying that the 4d band is filled [60].…”

Acetylene hydrogenation over structured Au–Pd catalysts

“…In principle, when the shell is relatively thin, the electronic properties of the shell metal may be perturbed, which offers exciting possibilities with regards to adsorption and catalytic behaviour. [56][57][58] In-spite of the obvious appeal, synthesis methods rarely seem to produce only core-shell nanoparticles. Instead, a mixture of coreshell, bimetallic and monometallic particles are oen formed, making evaluation of the catalytic properties of individual species challenging.…”

Promotion Mechanisms of Au Supported on TiO2 in Thermal- and Photocatalytic Glycerol Conversion

“…Meanwhile, hydrogen production via photocatalytic glycerol reforming under UV or solar irradiation under ambient conditions has been also investigated and is considered as a promising green energy source. , In order to overcome the low quantum efficiency of pristine photocatalysts, incorporation of various semiconductor heterojunctions and metal–semiconductor interfaces has been widely explored. − It has been reported that engineering the size, microstructure, and chemical composition of the promoters and the semiconductor support all influences the charge transfer kinetics of the photogenerated charge carriers, resulting in significant variations in the H 2 production rate. ,, A mechanistic study on noble-metal-modified TiO 2 reveals that photoreforming of glycerol mainly occurs via the oxidative C–C cleavage, resulting in the formation of glycolaldehyde and formaldehyde as the dominant products (61%) . Meanwhile, the oxidation of primary or secondary carbon leads to the formation of glyceraldehyde (26%) or dihydroxyacetone (13%), respectively.…”