Operando XANES Reveals the Chemical State of Iron-Oxide Monolayers During Low-Temperature CO Oxidation.

We have used grazing incidence X-ray absorption near edge spectroscopy (XANES) to investigate the behavior of monolayer FeO films on Pt(111) under near ambient pressure CO oxidation conditions with a total gas pressure of 1 bar. Spectra indicate reversible changes during oxidation and reduction by O and CO at 150 °C, attributed to a transformation between FeO bilayer and FeO trilayer phases. The trilayer phase is also reduced upon heating in CO+O , consistent with a Mars-van-Krevelen type mechanism for CO oxidation.

Formation of Epitaxial PdO(100) During the Oxidation of Pd(100).

The catalytic oxidation of CO and CH can be strongly influenced by the structures of oxide phases that form on metallic catalysts during reaction. Here, we show that an epitaxial PdO(100) structure forms at temperatures above 600 K during the oxidation of Pd(100) by gaseous O atoms as well as exposure to O-rich mixtures at millibar partial pressures. The oxidation of Pd(100) by gaseous O atoms preferentially generates an epitaxial, multilayer PdO(101) structure at 500 K, but initiating Pd(100) oxidation above 600 K causes an epitaxial PdO(100) structure to grow concurrently with PdO(101) and produces a thicker and rougher oxide.

Effect of Different InO(111) Surface Terminations on CO Adsorption.

InO-based catalysts have shown high activity and selectivity for CO hydrogenation to methanol; however, the origin of the high performance of InO is still unclear. To elucidate the initial steps of CO hydrogenation over InO, we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO on the InO(111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature.

The Oxygen Evolution Reaction Drives Passivity Breakdown for Ni-Cr-Mo Alloys.

Corrosion is the main factor limiting the lifetime of metallic materials, and a fundamental understanding of the governing mechanism and surface processes is difficult to achieve since the thin oxide films at the metal-liquid interface governing passivity are notoriously challenging to study. In this work, a combination of synchrotron-based techniques and electrochemical methods is used to investigate the passive film breakdown of a Ni-Cr-Mo alloy, which is used in many industrial applications. This alloy is found to be active toward oxygen evolution reaction (OER), and the OER onset coincides with the loss of passivity and severe metal dissolution.

Atomic Layer Grown Zinc-Tin Oxide as an Alternative Buffer Layer for CuZnSnS-Based Thin Film Solar Cells: Influence of Absorber Surface Treatment on Buffer Layer Growth.

Zn Sn O (ZTO) deposited by atomic layer deposition has shown promising results as a buffer layer material for kesterite CuZnSnS (CZTS) thin film solar cells. Increased performance was observed when a ZTO buffer layer was used as compared to the traditional CdS buffer, and the performance was further increased after an air annealing treatment of the absorber. In this work, we study how CZTS absorber surface treatments may influence the chemical and electronic properties at the ZTO/CZTS interface and the reactions that may occur at the absorber surface prior to atomic layer deposition of the buffer layer.