Density Functional Theory Study of Sulfur Adsorption at the (001) Surface of Metal-Rich Nickel Phosphides: Effect of the Ni/P Ratio

Abstract

A significant increase of the sulfur uptake by Ni x P with an increasing Ni to P ratio from 2 to 3 was reported recently in ultradeep adsorption desulfurization (ADS) of diesel fuel. It corresponded to increased Ni x P surface coverage, while no bulk Ni−P−S phases were identified. Density functional theory is applied in this communication to calculate the adsorption energies for S adatoms adsorbed on the surface of Ni2P, Ni12P5, and Ni3P phases. The preferable (001) surface-terminated slabs are considered to link the coverage tendency with the peculiarities of the electron density of states at the Fermi energy. The electron charge redistribution due to the adsorption of S atoms is calculated, and the nature of bonding of S with the substrates is discussed. The combination of ab initio calculations performed in the ground state for the considered systems with statistical thermodynamics renders the possibility to obtain the coverage at the temperatures beyond T = 0 K in good agreement with experimental data. The increase of surface coverage of Ni x P phases with an increase in the x value is the result of fine interplay between the number of possible sites for S adsorption and the difference in the adsorption energies for these sites.

A DFT study of the adsorption energy and electronic interactions of the SO2 molecule on a CoP hydrotreating catalyst

“…Moreover, the magnitude of the DOS at E f serves as indicator for the ability to form bonds with adsorbed species. 27 The DOS for the other surfaces can be seen in Fig. S16–S19 in the ESI.…”

“…85,86 According to the additionally included information for the specic orbitals for each element type, it can be seen that the PDOS of P in the valence and conduction bands are mainly due to p-orbitals, while the major contributor of the interactions is the partially lled d-orbitals of cobalt. In addition, there is overlap between the cobalt 3d-orbitals and phosphorus 3porbitals in the range of À3.1 to À5.3 eV, indicating hybridisation 27 and ensuring stability and strong adsorption of a molecule on the electronically active CoP surface.…”

“…Furthermore, Fuks and coworkers 27 found that the Ni 3 P phase of the nickel phosphide family provides better adsorption for sulfur atoms. In addition, the sulfur coverage was maximum compared to Ni 2 P and Ni 12 P 5 on the (001) facet.…”

Towards nanoscaled gold phosphides: surface passivation and growth of composite nanostructures

“…Among these, the great potential of nanoscaled metal phosphides (M x P y ) has been recognized for photovoltaics (InP, Cd 3 P 2 ), [4][5][6] bio-labeling, 7 energy storage, [8][9][10][11] and catalysis. [12][13][14][15][16] While gold is one of the most beloved metals for nanoparticles synthesis due to the wide opportunities that tunable plasmon bands provided for optics, biolabelling, 17 Ramanenhanced spectroscopy, or theragnosis, 18 gold phosphide, on the other hand, has been scarcely investigated at the nanoscale. Bulk Au 2 P 3 is a monoclinic compound.…”

An Investigation of Ni2P Single Crystal Surfaces: Structure, Electronic State and Reactivity

“…Many efforts have been made to date to elucidate the surface properties of Ni2P 10 single crystal surfaces, using X-ray photoelectron spectroscopy (XPS) [22,23], scanning 11 tunneling microscopy (STM) [24][25][26][27][28], low-energy electron diffraction (LEED) [24][25][26][27][28][29][30], 12 photoemission electron microscopy (PEEM) [25], photoelectron diffraction [31] and 13 photoemission spectroscopy (PES) [30,[32][33][34][35]. Theoretical calculations using density 14 functional theory (DFT) [11,14,15,[36][37][38] have also played an important role in 15 understanding the catalytic properties of the surface. These studies have indicated that 16 the Ni2P single crystal surface is stabilized by reordering of the P atoms.…”