Platinum Nanoparticles on Gallium Nitride Surfaces: Effect of Semiconductor Doping on Nanoparticle Reactivity

Abstract

Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

PtOx-SnOx-TiO2 catalyst system for methanol photocatalytic reforming: Influence of cocatalysts on the hydrogen production

“…Commonly used techniques include in situ photodeposition [27,28] and deposition of pre-prepared metal colloids [29,30]. Traditional way for preparing supported metal nanoparticles is impregnation with the appropriate metal salt followed by high temperature hydrogenation [31].…”

Structural evolution in Pt/Ga-Zn-oxynitride catalysts for photocatalytic reforming of methanol

“…Commonly used techniques include in situ photodeposition [5,12,22] and deposition of pre-prepared metal colloids [23][24][25][26]. An easy and effective way for preparing co-catalysts is impregnation with the appropriate metal salt followed by calcination.…”

XPS for probing the dynamics of surface voltage and photovoltage in GaN

“…Earlier SPV measurements were mostly synchrotron based due to the needed brightness of the source [6][7][8][9][10], but combined with Xray microfocusing and fast accumulation tools, the new generation commercial XP spectrometers can also provide critical information about such materials and devices [11,12]. In a recent publication we reported on capturing of the transient surface photovoltage in n-and p-GaN by XPS where new information about the mechanism of the transients formed by illumination with a ∼50 mW violet (405 nm) laser was brought out and discussed [13].…”