Hyung Chul Ham

We present the role of Pd ensembles in the selective direct synthesis of H2O2 from H2 and O2 on a PdAu alloy surface based on periodic density functional theory calculations. Our calculations demonstrate that H2O2 formation is strongly affected by the spatial arrangement of Pd and Au surface atoms. In particular, Pd monomers surrounded by less active Au atoms that suppress O−O bond scission are primarily responsible for the significantly enhanced selectivity toward H2O2 formation on PdAu alloys

Abstract Minimizing the use of platinum (Pt) in proton exchange membrane fuel cells (PEMFCs) is crucial for expanding the PEMFC market. The most straightforward approach would be to reduce the size of Pt particles. However, small Pt clusters, particularly those <2 nm in size, typically exhibit reduced activity for the oxygen reduction reaction (ORR) due to the overly strong adsorption of oxygen intermediates. Additionally, these small Pt clusters tend to degrade more quickly, resulting in low

The catalytic oxidation of ethane using CO2 as a soft oxidant could facilitate the utilization of CO2 and ethane from the shale gas as a raw material to produce value-added ethylene via a dehydrogenation process. Pt and Ce species were supported on mesoporous zeolite containing surface framework defects, and the resulting supported catalysts were investigated for the oxidative dehydrogenation of ethane with CO2. Extended X-ray absorption fine structure and high-resolution transmission electron m

Using first principles calculations, we examine how the ensemble effect on the performance of bimetallic catalysts is affected by the change of surface electronic structure associated with their geometric parameters. We look at H2O2 formation from H2 and O2 based on three different Pd monomer systems including AuPd adlayers with a Pd monomer each on Pd(111) [AuPdM/Pd(111)] and Au(111) [AuPdM/Au(111)] and a 55-atom cluster with Au41Pd shell and Pd13 core [Au41Pd@Pd13]. Our calculations show that

LaCrO3 perovskite and transition-metal (Co, Rh, Ir)-doped perovskite-based catalysts were fabricated using the Pechini method and applied to the dry reforming reaction of CH4 using CO2. One of the prepared perovskite-based catalysts, the LaCr0.95Ir0.05O3−δ catalyst, showed the highest CH4 conversion (81%) at 750 °C via the preactivation of the catalyst with H2 gas. It also showed highly stable catalytic activity for 72 h without coke formation on the catalyst surface. Through X-ray photoelectron

Herein, binary heteronanosheets made of ultrathin ReS₂ nanosheets and reduced graphene oxide (RGO) with either a two-dimensional (2D) "sheet-on-sheet" architecture (2D ReS₂/RGO) or a three-dimensional hierarchical structure (3D ReS₂/RGO) are constructed through rational structure-engineering strategies. In the resultant 3D ReS₂/RGO heteronanosheets, the ultrathin ReS₂ nanosheets are bridged on the RGO surface through Re-O bonds in a vertical

We present a theoretical explanation on how PdAu alloy catalysts can enhance the oxidation of CO molecules based on density functional theory calculations of CO adsorption and oxidation on AuPd/Pd(111) surfaces. Our study suggests that the enhanced activity is largely attributed to the possible existence of "partially-poisoned" Pd ensembles that accommodate fewer CO molecules than Pd atoms. Whereas the oxidation of preadsorbed CO is likely governed by O2 trapping, our study shows that small Pd e

Based on a combined density functional theory and experimental study, we present that the electrochemical activity of Pd3Co alloy catalysts toward oxygen reduction reaction (ORR) can be enhanced by adding a small amount of Ir. While Ir tends to favorably exist in the subsurface layers, the underlying Ir atoms are found to cause a substantial modification in the surface electronic structure. As a consequence, we find that the activation barriers of O/OH hydrogenation reactions are noticeably lowe