Behavior of S, SO, and SO3 on Pt (001), (011), and (111) surfaces: A DFT study

Abstract

In the hybrid sulphur (HyS) cycle, the reaction between SO 2 and H 2 O is manipulated to produce hydrogen, with water and sulphuric acid as by-products. However, sulphur poisoning of the catalyst has been widely reported to occur in this cycle, which is due to strong chemisorption of sulphur on the metal surface. The catalysts may deactivate as a result of these impurities present in the reactants or incorporated in the catalyst during its preparation and operation of the HyS cycle.Here, we report a density functional theory (DFT) investigation of the interaction between S, SO and SO 3 with the Pt (001), ( 011) and ( 111) surfaces. First, we have investigated the adsorption of single gas phase molecules on the three Pt surfaces. During adsorption, the 4F hollow sites on the (001) and (011) surfaces and the fcc hollow site on the (111) surface were preferred. S adsorption followed the trend of (001) 4F > (011) 4F > (111) fcc , while SO adsorption showed (001) 4F > (011) bridge/4F > (111) fcc and SO 3 adsorption was most stable in a S,O,O bound configuration on the (001) 4F > (011) 4F > (111) fcc sites.The surface coverage was increased on all the surfaces until a monolayer was obtained. The highest surface coverage for S shows the trend (001) S = (111) S > (011) S , and for SO it is (001) SO > (011) SO > (111) SO , similar to SO 3 where we found (001) SO3 > (011) SO3 > (111) SO3 . These trends indicate that the (001) surface is more susceptible to S species poisoning. It was also evident that both the (001) and (111) surfaces were reactive towards S, leading to the formation of S 2 . High coverage of SO 3 showed the formation of SO 2 and SO 4 , especially on the (011) surface. The thermodynamics indicated that an increased temperature up to 2000 K resulted in Pt surfaces fully covered with elemental S. The SO coverage showed θ ≥ 1.00 on both the (001) and (011) surfaces, and θ = 0.78 for the (111) in the experimental region where the HyS cycle is operated. Lower coverages of SO 3 were observed due to the size of the molecule.

A DFT Study of Ruthenium fcc Nano-Dots: Size-Dependent Induced Magnetic Moments

“… is the average adsorption energy of the H 2 per molecule adsorbed onto the Ru nano-dot and was calculated as [ 59 , 60 , 61 , 62 ]: where is the energy of the Ru nano-dot with adsorbed H atom (i.e., half the H 2 molecule), is the energy of the clean Ru nano-dot and is the gas phase energy of the free H 2 molecule.…”