Surface Science最新文献

Throughout its relatively short lifetime, ultra-high vacuum (UHV) surface chemistry has progressed quickly. In the 1960′s, pioneers like Ertl and Somorjai started the field using single crystals and gained significant insight into catalytic processes by relating surface structure to reactivity. The more recent proliferation of scanning probes has significantly increased the power of the single crystal approach by enabling the atomic-scale structure of active sites to be correlated with their reactivity. In this perspective we briefly discuss how the field developed, identify some challenges, and highlight Single-Atom Alloys (SAAs), a new class of heterogeneous catalyst that was developed from a fundamental surface science approach. However, despite recent successes, funding for fundamental surface science has declined. Academic hires in the discipline are also declining in part due to the start-up costs. We make the case that fundamental UHV surface chemistry is still too young a field to be in recession.

Curved crystals may feature a smooth transition between different vicinal surfaces. Using one curved single crystal to study different vicinal surfaces requires less experimental time than using several single flat crystals. Here, we study step distributions on the (110) plane of a curved NiAl single-crystal surface, which consists of alternating Ni and Al atom rows. We use scanning tunneling microscopy under UHV conditions at room temperature and our home-built Python-based analysis script to obtain statistical information on kink and straight sections along step-edge distributions from STM images. We perform this analysis mainly to study this single crystal’s kink distributions and step termination We propose a new method to estimate the step formation energy based on step edge analysis and statistical mechanics. With this method, we find an approximation of the step formation energy for NiAl(110).

We report on the chemical composition, bonding, and in-vacuum thermal stability (up to 1000 °C) of nitrogen plasma terminated H-Diamond(111) (H-Di(111)) surfaces followed by ambient exposure. The nitrogen-plasma exposures include radio frequency (RF) (at pressure: 3 × 10⁻² (damaging) and 7 × 10⁻² Torr (non-damaging)) and microwave (MW) nitrogen plasmas and studied by X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS). The largest nitrogen intake was observed upon exposure to RF(N₂) damaging plasma, followed by MW(N₂) and non-damaging RF(N₂) plasmas. A similar trend follows the adsorption of adventitious oxygen. The XPS analysis shows that most of the adventitious oxygen is adsorbed in a CO_x configuration upon nitride surfaces exposure to ambient conditions. However, upon high temperature annealing of the damaging RF(N₂) plasma exposed surface, some NO_x (species) were detected by XPS. From the HREELS analysis, the hydrogen adsorbed on the H-Di(111) is not fully removed by exposure to the different nitrogen plasmas. These measurements show that NH(ads) species are formed on the surface and are desorbed upon vacuum annealing in the 500–700 °C range. This study may be of importance in all ex-situ applications influenced by the near-surface physicochemical and electronic properties of nitrogen-terminated H-Di(111) surfaces.

A brief review is presented of the development and application of quantitative structural studies of surfaces in the last 60 years. The development of the earliest method, and the one that remains the benchmark technique, namely quantitative low energy electron diffraction (QLEED) is described, and its underlying methodology compared with alternative techniques that have emerged subsequently. In particular, the role of scanning tunnelling microscopy (STM) and density functional theory (DFT), a combination of methods that has typified many more recent surface structural studies, is compared and contrasted with ‘traditional’ quantitative experimental methods such as QLEED.

Two-dimensional antimonene with a honeycomb structure has attracted significant attention in recent years due to its novel properties and tunable electronic structure as varying applied in-plane strain. Yet, applying epitaxially strained antimonene is greatly limited by the strong coupling with the metal substrates. Here, we demonstrate the synthesis of the van der Waals stretched antimonene on graphene/Cu(111) substrate via remote epitaxy. It is found that, as corroborated by atomic force microscopy and reflection high-energy electron diffraction, the lattice of the antimonene can be remotely stretched by the underlying Cu(111). The graphene layer prevents antimonene from forming the surface alloy with Cu(111), which is also confirmed by Raman spectroscopy results. Our study not only provides a way to regulate the lattice of the epitaxial layers remotely but also provides a new idea for developing new potential topological materials.

The existing energy crisis and environmental pollution require an innovative approach to hydrogen production. Photocatalytic water-splitting has emerged as a potential solution, but the development of efficient photocatalysts remains the key challenge. Here, we employ first-principles calculations to investigate the structural, electronic, optical and photocatalytic characteristics of a van der Waals heterojunction comprising GaTe and AsP monolayers. The constructed GaTe/AsP heterojunction is thermodynamic, dynamical and thermal stable. The smaller indirect bandgap 1.68 eV than 2.21 eV and 2.45 eV for the constituent GaTe and AsP monolayers respectively, enhances the optical absorption of the GaTe/AsP heterojunction in visible and ultraviolet (UV) regions. The type-II band alignment of the GaTe/AsP heterojunction makes an efficient separation of photogenerated electrons and holes to different layers and extension their lifespans. The built-in electric field from GaTe side to AsP side induces a direct Z-scheme heterojunction photocatalyst with high redox reaction kinetic and high solar-to-hydrogen efficiency of 14.10 %. Our study demonstrates that the GaTe/AsP heterostructure is as efficient photocatalysts for overall water-splitting.

The photocatalytic efficiency of traditional photocatalysts is usually frustrated by the easy recombination of photogenerated carriers and the lack of good compatibility between strong redox capacity and light response range. Two-dimensional (2D) Z-scheme heterostructures photocatalysts can solve these problems well. Based on first principles, the photocatalytic properties of 2D MoSeO/Boron phosphide (BP) heterostructures are systematically investigated. The results show that O-Mo-Se/BP heterostructure (with Se atoms close to BP layer) is a traditional type-II heterostructure, which lacks the redox capacity for photocatalytic water decomposition. However, Se–Mo–O/BP heterostructure (with O atoms close to BP layer) is a Z-scheme heterostructure, the built-in electric field can effectively separate the photogenerated carriers with higher redox ability. Meanwhile, the band edge positions with higher redox capacity straddle the water redox potentials for water splitting. Optical absorption shows that the heterostructure has a good light absorption capacity in UV–visible region. The power conversion efficiency (PCE) for this heterostructure is 15.9 %, which can be further improved to 18.7 % under external electric field. These results indicate that Se–Mo–O/BP heterostructure is a compelling direct Z-scheme candidate for photocatalytic water splitting.

Infrared Reflection-Absorption Spectroscopy (IRRAS), a pivotal tool in the study of the surface chemistry of metals, has recently also gained substantial impact for oxide surfaces, despite the inherent challenges originating from their dielectric properties. This review focuses on the application of IRRAS to ceria (CeO₂), a metal oxide for which a significant amount of experimental data exists. We elaborate on the differences in optical properties between metals and metal oxides, which result in lower intensity of adsorbate vibrational bands by approximately two orders of magnitude and polarization-dependent shifts of vibrational frequencies. We examine how the surface selection rule, governing IR spectroscopy of adsorbates on metals, contrasts sharply with the behavior of dielectrics where both positive and negative vibrational bands can occur, and how IRRAS can capture vibrations with transition dipole moments oriented parallel to the surface—a capability not feasible on metallic surfaces. Finally, this paper explores the broader implications of these findings for enhancing our understanding of molecule interactions on oxide surfaces, and for using IR spectroscopy for operando studies under technologically relevant conditions.

The dual-atom dimer with half-filled 3d orbital demonstrates a great advantage in electrochemical degradation from nitrate to ammonia, because their binding interaction and electron transfer between reactants and active sites are spin-dependent. Herein, we suggest a local structure distortion caused by a bimetallic hybridization to regulate the spin configuration from low to high by implanting one Fe atom into the Mn/Mn dimer on holey nitrogen-doped graphene, which makes the Mn magnetic moment increase to 3.31 μ_B from 0.48 μ_B. Meanwhile, the activation energy of the formed *NOH at rate-limiting step can be decreased to 0.79 eV, which is obviously lower than the pristine Fe/Fe (1.38 eV) and Mn/Mn (1.12 eV) dimers. These findings enlighten an intriguing strategy to enhance the reactive activity of dual-atom catalysts by regulating their spin configuration.