Chemisorption

About: Chemisorption is a research topic. Over the lifetime, 16298 publications have been published within this topic receiving 554989 citations.

Adsorption and decomposition of dimethyl methylphosphonate on an aluminum oxide surface

Abstract: Etudes, par spectroscopie electronique tunnel inelastique, de l'adsorption de dimethyl methylphosphonate sur des couches minces d'alumine

2,4-Diamino-5-(phenylthio)-5H-chromeno [2,3-b] pyridine-3-carbonitriles as green and effective corrosion inhibitors: gravimetric, electrochemical, surface morphology and theoretical studies

Abstract: The inhibition of mild steel corrosion in 1 M HCl by three newly synthesized 2,4-diamino-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitriles (DHPCs) namely, 2,4-diamino-7-nitro-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (DHPC-1), 2,4-diamino-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (DHPC-2) and 2,4-diamino-7-hydroxy-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (DHPC-3) was studied using weight loss method, electrochemical techniques, surface morphology (SEM, AFM) studies and theoretical (quantum chemical calculations and molecular dynamic simulation) methods. The weight loss and electrochemical measurements showed that the inhibition efficiency increases with increasing inhibitor concentration and the relative trend of inhibition performance is DHPC-3 > DHPC-2 > DHPC-1. A potentiodynamic polarization study reveals that the investigated DHPCs act as mixed type inhibitors. The adsorption of the DHPCs on the mild steel surface obeys the Langmuir adsorption isotherm and involves both physisorption and chemisorption modes. The presence of the electron releasing –OH group at position seven on the chromenopyridine ring is considered to be responsible for the highest inhibition efficiency of DHPC-3 among the studied compounds. Whereas the presence of the electron withdrawing nitro (–NO2) group at position seven on the chromenopyridine ring is responsible for the lowest inhibitive strength of DHPC-1. Quantum chemical calculations and molecular dynamic simulation studies were undertaken to provide mechanistic insight into the roles of the different substituents (–OH and –NO2) on the corrosion inhibition behavior of the studied inhibitors.

Surface chemistry of tin oxide based gas sensors

Abstract: Four types of gas sensors based on SnOx thin film with and without additives (Pt and Sb) were investigated by means of x‐ray photoelectron spectroscopy and scanning Auger microscopy. The sensors were deposited on Si substrates by using reactive dc magnetron sputtering. The temperature dependencies of the electrical resistivity response to CO gas exposure were measured in order to characterize all types of fabricated sensors. The surface chemical composition before and after various treatments (Ar+ ion sputtering, thermal annealings in ultrahigh vacuum, and oxygen up to 400 °C) was determined from core level and valence band spectra. The three main types of oxygen species were found on the sensors’ surface: oxygen in SnOx, adsorbed hydroxyl groups and adsorbed water. An ultrathin Pt overlayer, which enhances the gas sensitivity in a low operating temperature range, was found to be very porous. The addition of a Pt overlayer was promoting a formation of hydroxyl groups, while the surface oxygen species was independent of the Sb doping. The obtained results support the assumption that the changes of the sensors’ resistivity under reducing gas exposure are caused more by the change of the surface defects’ density than by variation of excess surface charge induced by adsorbed oxygen species.