Ethanol oxidation on Pt is a typical multistep and multiselectivity heterogeneous catalytic process. A comprehensive understanding of this fundamental reaction would greatly benefit design of catalysts for use in direct ethanol fuel cells and the degradation of biomass-derived oxygenates. In this work, the reaction network of ethanol oxidation on different Pt surfaces, including close-packed Pt{111}, stepped Pt{211}, and open Pt{100}, is explored thoroughly with an efficient reaction path searching method, which integrates our new transition-state searching technique with periodic density functional theory calculations. Our new technique enables the location of the transition state and saddle points for most surface reactions simply and efficiently by optimization of local minima. We show that the selectivity of ethanol oxidation on Pt depends markedly on the surface structure, which can be attributed to the structure-sensitivity of two key reaction steps: (i) the initial dehydrogenation of ethanol and (ii) the oxidation of acetyl (CH3CO). On open surface sites, ethanol prefers C-C bond cleavage via strongly adsorbed intermediates (CH2CO or CHCO), which leads to complete oxidation to CO2. However, only partial oxidizations to CH3CHO and CH3COOH occur on Pt{111}. Our mechanism points out that the open surface Pt{100} is the best facet to fully oxidize ethanol at low coverages, which sheds light on the origin of the remarkable catalytic performance of Pt tetrahexahedra nanocrystals found recently. The physical origin of the structure-selectivity is rationalized in terms of both thermodynamics and kinetics. Two fundamental quantities that dictate the selectivity of ethanol oxidation are identified: (i) the ability of surface metal atoms to bond with unsaturated C-containing fragments and (ii) the relative stability of hydroxyl at surface atop sites with respect to other sites.

As an important class of catalytic reactions, the reaction at solid/liquid interfaces is less understood at the atomic level. From a theoretical point of view, the difficulty lies at the simultaneous consideration of the extended solid surface and the dynamic liquid environment. In taking the oxidation of formic acid (HCOOH f CO 2 + H 2 ) at the Pt(111)/H 2 O interface as the model system that has great potentials in direct fuel cells applications, this work combines density functional theory (DFT) slab calculations with a continuum solvation model to simulate the reactions at the metal/H 2 O interface for the first time. The solvation effect is treated by including (i) a few explicit water molecules as the core solvation shell and (ii) an implicit continuum solvation model to take into account the long-range electrostatic interaction from water solution. We show that formic acid can be directly oxidized to CO 2 only in the presence of preadsorbed formate. Although the formate itself can not be oxidized to CO 2 at mild conditions, it helps to stabilize the formic acid adsorption configuration with the CH bond in contact with the Pt surface, which is the precursor leading to CO 2 . Without the preadsorbed formate, formic acid is only able to adsorb with its carboxyl O linking to Pt, which is however difficult to decompose further. By electronic structure analyses, we show that a hydrophobic zone formed nearby the preadsorbed fomate on Pt(111) is the origin for the promoting role of formate, which demonstrates that catalytic reactions at solid/water interface can be significantly affected by modifying the affinity between surface and water.

The non-coding RNA subunit of telomerase provides the template for telomerase activity. In diverse fungi, 3' end processing of telomerase RNA involves a single cleavage by the spliceosome. Here, we examine how human telomerase RNA (hTR) primary transcripts are processed into the mature form of precisely 451 nt. We find that the splicing inhibitor isoginkgetin mimics the effects of RNA exosome inhibition and causes accumulation of long hTR transcripts. Depletion of exosome components and accessory factors reveals functions for the cap binding complex (CBC) and the nuclear exosome targeting (NEXT) complex in hTR turnover. Whereas longer transcripts are predominantly degraded, shorter precursor RNAs are oligo-adenylated by TRF4-2 and either processed by poly(A)-specific ribonuclease (PARN) or degraded by the exosome. Our results reveal that hTR biogenesis involves a kinetic competition between RNA processing and degradation and suggest treatment options for telomerase insufficiency disorders.

Self-consistent periodic slab calculations based on gradient-corrected density functional theory (DFT-GGA) were conducted to investigate the potential energy diagram for ethanol oxidation over Pt (111). Ethanol oxidation on Pt is found to be dominated by an one-step concerted dehydrogenation pathway to produce acetaldehyde, which is about 600 times faster than the traditionally regarded stepwise pathways. The same mechanism is transferable to methanol oxidation but with a minor contribution. The results can help to clarify the longstanding puzzles on the selectivity of direct alcohol fuel cell over Pt.