Edge-exposed MoS2 nano-assembled structures are designed for high hydrogen evolution reaction activity and long term stability. The number of sulfur edge sites of nano-assembled spheres and sheets is confirmed by Raman spectroscopy and EXAFS analysis. By controlling the MoS2 morphology with the formation of nano-assembled spheres with the assembly of small-size fragments of MoS2, the resulting assembled spheres have high electrocatalytic HER activity and high thermodynamic stability.

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 compared to that on the monometallic Pd and Au counterparts.

The electrochemical synthesis of NH 3 by the nitrogen reduction reaction (NRR) at low temperature (<65 °C) and atmospheric pressure using nanosized γ-Fe 2 O 3 electrocatalysts were demonstrated. The activity and selectivity of the catalyst was investigated both in a 0.1 M KOH electrolyte and when incorporated into an anion-exchange membrane electrode assembly (MEA). In a half-reaction experiment conducted in a KOH electrolyte, the γ-Fe 2 O 3 electrode presented a faradaic efficiency of 1.9% and a weight-normalized activity of 12.5 nmol h −1 mg −1 at 0.0 V RHE . However, the selectivity toward N 2 reduction decreased at more negative potentials owing to the competing proton reduction reaction. When the γ-Fe 2 O 3 nanoparticles were coated onto porous carbon paper to form an electrode for a MEA, their weight-normalized activity for N 2 reduction was found to increase dramatically to 55.9 nmol h −1 mg −1 . However, the weight-and area-normalized N 2 reduction activities of γ-Fe 2 O 3 decreased progressively from 35.9 to 14.8 nmol h −1 mg −1 and from 0.105 to 0.043 nmol h −1 cm −2 act , respectively, during a 25 h MEA durability test. In summary, a study of the fundamental behavior and catalytic activity of γ-Fe 2 O 3 nanoparticles in the electrochemical synthesis of NH 3 under low temperature and pressure is presented.

Density functional theory studies demonstrate that defective graphene-supported Cu nanoparticles can modify the structural and electronic properties of copper for enhancing electrochemical reduction of carbon dioxide (CO2) into hydrocarbon fuels (CH4, CO, and HCOOH). We not only provide improved understanding of CO2 conversion mechanisms on both Cu and the Cu nanoparticle system, but also explain a key factor for enhanced CO2 conversion. A promising catalytic material for CO2 conversion into hydrocarbon fuels may allow for geometry flexibility upon interaction with a key intermediate of CHO*.

The amount of anthropogenic CO2 emission keeps increasing worldwide, and it urges the development of efficient CO2 capture technologies. Among various CO2 capture methods, adsorption is receiving more interest, and carbonaceous materials are considered good CO2 adsorbents. There have been many studies of N-containing carbon materials that have enhanced surface interaction with CO2; however, various N-containing functional groups existing in the carbon surface have not been investigated in detail. In this study, first-principle calculations were conducted for carbon models having various N-functional groups to distinguish N-containing heterogeneity and understand carbon surface chemistry for CO2 adsorption. Among N-functional groups tested, the highest adsorption energies of −0.224 and −0.218 eV were observed in pyridone and pyridine groups, respectively. Structural parameters including bond angle and length revealed an exceptional hydrogen-bonding interaction between CO2 and pyridone group. Charge accumulation on CO2 during interaction with pyridine-functionalized surface was confirmed by Bader charge analysis. Also, the peak shift of CO2 near Fermi level in the DOS calculation and the presence of HOMO on pyridinic-N in the frontier orbital calculation determined that the interaction of pyridinic-N is weak Lewis acid–base interaction by charge transfer. Furthermore, adsorption energies of N2 were calculated and compared to those of CO2 to find its selective adsorption ability. Our results suggest that pyridone and pyridine groups are most effective for enhancing the interaction with CO2 and have potential for selective CO2 adsorption.

Supported gold nanoparticles have recently been shown to possess intriguing catalytic activity for hydrogenation reactions, particularly for selective hydrogenation reactions. However, fundamental studies that can provide insight into the reaction mechanisms responsible for this activity have been largely lacking. In this tutorial review, we highlight several recent model experiments and theoretical calculations on a well-structured gold surface that provide some insights. In addition to the behavior of hydrogen on a model gold surface, we review the reactivity of hydrogen on a model gold surface in regards to NO2 reduction, chemoselective C=O bond hydrogenation, ether formation, and O-H bond dissociation in water and alcohols. Those studies indicate that atomic hydrogen has a weak interaction with gold surfaces which likely plays a key role in the unique hydrogenative chemistry of classical gold catalysts.

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The critical role of the Ag–Pd ligand effect (which is tuned by changing the number of Pd atomic layers) in determining the dehydrogenation and dehydration of HCOOH on the bimetallic Pd/Ag catalysts was elucidated by using the spin-polarized density functional theory (DFT) calculations. Our calculations suggest that the selectivity to H2 production from HCOOH on the bimetallic Pd/Ag catalysts strongly depends on the Pd atomic layer thickness at near surface. In particular, the thinnest Pd monolayer in the Pd/Ag system is responsible for enhancing the selectivity of HCOOH decomposition toward H2 production by reducing the surface binding strength of specific intermediates such as HCOO and HCO. The dominant Ag–Pd ligand effect by the substantial charge donation to the Pd surface from the subsurface Ag [which significantly reduce the density of state (particularly, d z 2 –r 2 orbital) near the Fermi level] proves to be a key factor for the selective hydrogen production from HCOOH decomposition, whereas the expansive (tensile) strain imposed by the underlying Ag substrate plays a minor role. This work hints on the importance of properly engineering the surface activity of the Ag–Pd core–shell catalysts by the interplay between ligand and strain effects.