Methanol electro-oxidation and induced sintering on Pt nanoclusters supported on thin-film Al2O3/NiAl(100)

Temperature-Dependent Oxidation of Pt Nanoclusters on a Thin Film of Al2O3 on NiAl(100)

“…Standard electrochemical equipment was used to sweep the potential. The experimental details are reported elsewhere . Adsorption of methanol was performed at sample temperature 120 K. Methanol gas was admitted into the UHV chamber through a leak valve with background pressure 1 × 10 −8 torr.…”

“…In the present work, we investigated the interaction of Pt nanoclusters with a thin film of Al 2 O 3 grown on NiAl(100) at various temperatures, with surface-probe techniques including synchrotron-based photoelectron spectroscopy (PES), scanning tunneling microscopy (STM), and reflection high-energy electron diffraction (RHEED). This Pt/Al 2 O 3 system attracts much research − because of its prospective application in important technologies, such as petroleum treatment, fuel cells and NO x reduction. − The Pt clusters, grown from vapor deposition on the Al 2 O 3 /NiAl(100), had mean diameter 2.2 nm and height 0.4 nm, and were shown to undergo a temperature-dependent oxidation, in the absence of a gaseous oxidizing agent. Upon the formation of Pt clusters on the oxide at 300 K, the electronic structure of the Al 2 O 3 thin film alters significantly: the Al 2p (Al ox 2p) and O 1s photoelectron signals from Al 2 O 3 shifted 0.4−0.5 eV toward smaller binding energy (BE), indicating a transfer of charge from the Pt clusters to the oxide, so that the Pt clusters become partially oxidized.…”

“…Formation of a Pt x Al y O z complex , after annealing is thus proposed for the observations. The new Pt oxide bonding became substantially stronger, as it resisted cluster agglomeration induced in a cyclic voltammetric (CV) process and structural alterations that occur on pristine Pt clusters (grown at 300 K and before annealing) . The further oxidized Pt clusters retained an ordered structure (Pt(001)[110]//Al 2 O 3 (100)[010]), indicated by the STM and RHEED measurements, but were covered with oxide materials (Al x O y ), indicated by the adsorbed methanol that exhibited a bonding state resembling that on Al 2 O 3 .…”

Characterization of Thin MgO Films on Ag(001) by Low-Energy Electron Diffraction and Scanning Tunneling Microscopy

“…Thin metal oxide films like MgO thin films are of great interest for technological applications where they are used as insulating barriers in microelectronic devices. − In catalysis, magnesium oxide is an important support for metal clusters. − Much attention has been paid to the catalytic activity of metal clusters supported on bulk oxide surfaces − but also on thin oxide films. − With respect to thin MgO films on Ag(001), many research groups have studied the strain relaxation, − interface properties, − electronic density of states, defects, − structure, ,− and hydroxylation . An important advantage of such thin films is that standard surface techniques like scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), atomic emission spectroscopy, or ultraviolet photoelectron spectroscopy can be used because of the conducting character of the film-support system.…”

Recent Advances in the Synthesis, Properties, and Biological Applications of Platinum Nanoclusters

“…Even the amount of Pt was quite small, the electrocatalytical activity was improved dramatically and the ampere-metric determination limit of sodium nitrite (NaNO 2 ) was 0.067 μM (S/N = 3). On the other hand, a doped substrate method is allowing Pt NCs doped or dispersed into the substrate materials such as polymer film [89][90][91][92], inorganic substrate [93][94][95][96], metal organic framework (MOF) [97], carbon nanotubes (CNTs) [98,99], and graphene [100][101][102], which could easily adjust and enhance the pure NCs' chemical and physical performance. Pt NCs with an average diameter of 0 7 ± 0 3 nm were deposited on SmMn 2 O 5 (SMO) mullite-type oxides by an atomic layer deposition method (ALD), showing the efficient ability to solve the CO poisoning problem for the Pt-based catalyst [103].…”