Phosphorous (P) diffusion in bulk Ni 2 P was investigated by the density functional theory (DFT) to find the origin of the low-temperature P diffusion into the surface. The Ni 2 P bulk structure consists of two types of layers, Ni 3 P 2 and Ni 3 P 1 , stacked along the [0001] direction. Two types of P vacancies in Ni 2 P were studied: V 1 P (P deficient in N 3 P 2 ) and V 2 P (P deficient in N 3 P 1 ). V 1 P was a slightly more stable point defect than V 2 P by 0.20 eV. The P diffusions to vacancies (V 1 P and V 2 P ) had large diffusion barriers of more than 1 eV, except the P diffusion path along the [0001] direction through an interstitial site in Ni 3 P 1 (I 1→2 P ) and then to V 1 P , which showed the lowest energy barrier of about 0.18 eV. The DFT calculations suggested that the two adjacent vacancies (both V 1 P ) allow the local rearrangement of the structure to form a tetrahedral structure at the intermediate state. We have proposed a new diffusion mechanism in the intermetallic compound named the interstitial−vacancy diffusion mechanism.

The gas-phase catalytic hydrodeoxygenation (HDO) of acetic acid (AA) over carbon-supported noble metals (5% M on Cp97, where M = Pt, Pd, Ru, or Rh) were studied. The temperature-dependent conversion and selectivity were studied at 1 atm from 200 to 400 °C. For Pt, Pd, and Rh, the main pathway from 200 to 300 °C was decarbonylation, and from 350 to 400 °C the main pathways were decarbonylation/decarboxylation and ketonization. For Ru, however, from 200 to 250 °C the main pathway was decarboxylation, and from 300 to 400 °C the main pathway was decarbonylation. The activity trend based on turnover frequency at 200 °C was found to be Ru > Rh ≈ Pt > Pd. The activities of all of the catalysts at 200 °C were found to decrease after reaction at 400 °C and a return to 200 °C. This is attributed to sintering and coking. The reaction orders in AA and H 2 measured at 200 °C for all of the catalysts are generally well below ∼0.5, suggesting relatively strong adsorption of both reactants on all of the metal surfaces. The temperature dependence of the reaction rates was examined over the range 200−240 °C, and apparent activation energies of around 21 kcal/mol were found for all of the catalysts since decarbonylation/ decarboxylation is the main pathway with similar product distribution.

Strong Electrostatic Adsorption (SEA) has been demonstrated as a simple, scientific method to prepare well dispersed Pt nanoparticles over typical forms of carbon: activated, black, and graphitic carbons. Many varieties of specialty carbons have been invented in the last few decades including multi-walled nanotubes, nanofibers, graphene nanoplatelets, etc. In this work, we explore whether SEA can be applied to these specialty carbons for the synthesis of Pt nanoparticles. Over a number of oxidized and unoxidized multiwalled nanotubes and nanofibers, the point of zero charge (PZC) was measured and the uptake of anionic Pt complexes (Pt hexachloride, [PtCl 6 ] 2− , and cationic Pt complexes (platinum tetraammine, [Pt(NH 3 ) 4 ] 2+ ) as functions of final pH were surveyed. Pt nanoparticles on the various supports were synthesized at the optimal pH and were characterized by x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The specialty carbons displayed volcano-shaped uptake curves typical of electrostatic adsorption for both Pt anions at low pH and Pt cations at high pH. However, the regimes of uptake often did not correspond to the measured PZC, probably due to surface impurities from the carbon manufacturing process. This renders the measured PZC of these specialty carbons unreliable for predicting anion and cation uptake. On the other hand, the anion and cation uptake curves provide an "effective" PZC and do indicate the optimal pH for the synthesis of ultrasmall nanoparticle synthesis. High resolution STEM imaging also showed that with SEA it is possible to disperse nanoparticles on the surface as well as the inner walls of the specialty carbons.