In-situ analysis of heterogeneous catalysts under reaction condition is indispensable to understand reaction mechanisms and nature of active sites. Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) is one of the powerful methods to investigate chemical states of catalysts and reaction intermediates adsorbed on the surface. In this review, reaction of carbon dioxide on Cu(997) and Zn-deposited Cu(997) surfaces are discussed as an example of surface chemistry of weakly adsorbed molecules, together with a brief overview of recent progress in AP-XPS methods.

Surface X-ray diffraction is a powerful tool for studying the atomic structure of buried interfaces nondestructively. The analysis is often limited to the static structures, since the acquisition of crystal truncation rod (CTR) profile dataset is lengthy. Recently, high-speed methods have been developed by several groups, aiming for the in operando study of interface phenomena. Our method uses energy-dispersive convergent X-rays and area detector, and allows the quantitative structure analysis during irreversible phenomena in a typical time frame of 1 s. In this review, the energy-dispersive method is compared with the other high-speed methods which use high-energy X-rays with a grazing incidence geometry and transmission geometry, and then two examples of the real-time monitoring are presented, the photo-induced wettability transition of the rutile-TiO₂(110) surface and an electrochemical reaction on the Pt(111) electrode surface, to show the capability of the energy-dispersive method.

Establishing an accurate view of the photocatalytic mechanism of titanium dioxide (TiO₂) has been a challenging task since the discovery of the Honda-Fujishima effect. Despite the great success of catalytic studies in elucidating the chemical and physical aspects of photocatalysis, many questions remain. A surface science approach, which is characterized by the use of atomically well-defined surfaces in precisely controlled environments, is a powerful tool to shed light on the fundamental mechanism, especially the dynamics of photoexcited carriers. In the present contribution, recent progress in photocatalytic research that correlates photocatalytic activity and carrier dynamics on rutile and anatase TiO₂ is reviewed. A special focus is placed on the lifetime of photoexcited carriers. We present a method to determine the carrier lifetime; pump-probe time-resolved soft X-ray photoelectron spectroscopy, utilizing an ultraviolet laser as a pump light and a synchrotron radiation as a probe light. The carrier lifetime is found to be linearly correlated with the photocatalytic decomposition/desorption rate of acetic acid adsorbed on single-crystal TiO₂ surfaces. The important role of a potential barrier on the TiO₂ surface, which influences the carrier lifetime and the photocatalytic activity, is discussed.

Raman spectroscopy provides a meaningful fingerprint for sensing and discriminating materials, and surface-enhanced Raman scattering (SERS) can dramatically increase Raman signals up to the single-molecule level of sensitivity. Graphene, a monolayer carbon sheet, has recently attracted considerable attention as a unique SERS substrate. However, there are various types of graphene materials, and the SERS application category is significantly correlated to the structure and quality of the graphene. This review provides a broad perspective on this research area, intended for researchers of diverse fields. First, we categorize the graphene-based SERS applications based on their structure. Second, we introduce the types of graphene (graphene oxide, reduced graphene oxide, chemical vapor deposited graphene, and carbon nanowalls) and their synthesis methods. Thereafter, we highlight state-of-the-art studies for each category of graphene-based SERS.

It's hard to imagine that we can take a splinter and sharpen it down to the atomic level. It's even more impressive that we can bring this sharp tip close to a surface, scan it over the surface, and be sensitive to the tiny forces between the apex atom and individual atoms on the surface. Measuring and interpreting these forces is the goal of high-resolution atomic force microscopy (AFM). We perform frequency-modulation AFM (FM-AFM), in which we oscillate the tip and record the change in frequency as a measure of the interaction with the surface. FM-AFM performed in vacuum with stiff sensors has lead to amazing discoveries. Now, we are returning to the challenge of imaging samples in device- and biologically-relevant conditions. This contribution summarizes work that was performed in the Giessibl group to image with atomic resolution in ambient and liquid environments. We demonstrated atomic resolution with the qPlus sensor on KBr, and followed this with investigations on graphitic surfaces. We have also shown single-atomic defects and steps on the calcite surface. [DOI: 10.1380/ejssnt.2018.351]