arXiv subjects

Maosheng Hao

Publications and source records attributed to Maosheng Hao.

3 recordsLinked to original sources

arXiv2026

Hydrogen Activation via Dihydride Formation on a Rh1/Fe3O4(001) Single-Atom Catalyst

Hydrogen activation is a key elementary step in catalytic hydrogenation. In heterogeneous catalysis, it usually proceeds through dissociative adsorption on metal nanoparticles followed by surface diffusion or spillover, whereas homogeneous catalysts activate H2 through dihydride or dihydrogen intermediates at a single metal center. Here, we show that isolated Rh adatoms supported on Fe3O4(001) activate hydrogen through formation of a stable dihydride species without atomic H spillover. Temperature-programmed desorption, X-ray photoelectron spectroscopy, and scanning tunneling microscopy collectively reveal strong (approximately 1 eV) hydrogen adsorption exclusively at isolated Rh1 sites, while isotope-exchange experiments further demonstrate that hydrogen remains localized. Density-functional theory based calculations indicate a barrierless conversion from molecular H2 to the dihydride, and random-phase approximation calculations further confirm the relative stability of the dihydride. Together, these results show that single-atom Rh sites cleave and bind H2 through a dihydride pathway analogous to homogeneous complexes, establishing a mechanistic bridge between homogeneous and heterogeneous catalysis.

cond-mat.mtrl-sci↗

arXiv2025

Identifying Electronic Doorway States in the Secondary Electron Emission from Layered Materials

We investigate the secondary low-energy electron emission induced by inelastic electron scattering from graphene and layered materials thereof. By applying a coincidence detection of the primary scattered and the emitted secondary electron we unravel pronounced resonance features otherwise overshadowed by the largely structureless secondary electron energy distribution. Supported by density functional theory calculations we show that these structures are the signature of prominent Feshbach resonances above the vacuum threshold which originate from interlayer states acting as a doorway state for electron emission. Remarkably, some of these doorway states open up only for samples with more than five layers.

cond-mat.mes-hall↗

arXiv2025

Multi-Technique Characterization of Rhodium Gem-Dicarbonyls on TiO$_2$(110)

Gem-dicarbonyls of transition metals supported on metal (oxide) surfaces are common intermediates in heterogeneous catalysis. While infrared (IR) spectroscopy is a standard tool for detecting these species on applied catalysts, the ill-defined crystallographic environment of species observed on powder catalysts renders data interpretation challenging. In this work, we apply a multi-technique surface science approach to investigate rhodium gem-dicarbonyls on a single-crystalline rutile TiO$_2$(110) surface. We combine spectroscopy, scanning probe microscopy, and Density Functional Theory (DFT) to determine their location and coordination on the surface. IR spectroscopy shows the successful creation of gem-dicarbonyls on a titania single crystal by exposing deposited Rh atoms to CO gas, followed by annealing to 200-250 K. Low-temperature scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) data reveal that these complexes are mostly aligned along the [001] crystallographic direction, corroborating theoretical predictions. Notably, x-ray photoelectron spectroscopy (XPS) data reveal multiple rhodium species on the surface, even when the IR spectra show only the signature of rhodium gem-dicarbonyls. As such, our results highlight the complex behavior of carbonyls on metal oxide surfaces, and demonstrate the necessity of multi-technique approaches for the adequate characterization of single-atom catalysts.

physics.chem-ph↗