In situ infrared attenuated total reflectance spectroelectrochemical study of lubricant degradation

Abstract

An attenuated total reflectance (ATR) infrared (IR) cell was designed using a boron-doped silicon wafer as the optically transparent electrode to simultaneously perform ATR-IR spectroscopic and electrochemical impedance measurements. The degradation of industrial lubricants was investigated by monitoring the near-surface concentration of hydrocarbons, detergents and anti-wear additives and the formation of degradation products, while polarizing the cell using electrochemical impedance spectroscopy (EIS). The detergent and the anti-wear agent concentration on and near the silicon surface, based on the IR spectra, and the sum of bulk solution and charge transfer resistance, based on the impedance spectra, were all at a maximum for 30 h drain oil, and then decreased for later drain oils. These results agree with other independent measurements, such as oil viscosity, total acid number (TAN), and total base number (TBN) to indicate that the lubricant is significantly degraded after 30 h in the engine test. These data demonstrate the potential use of the ATR silicon-based electrochemical cell as a monitoring device for lubricant degradation, and as an effective analytical tool capable of studying interfacial kinetics, surface interactions of the additives, and performance of silicon-based spectroelectrochemical devices.

In Situ Attenuated Total Reflectance Infrared Spectroelectrochemistry (ATR-IR-SEC) for the Characterization of Molecular Redox Processes on Surface-Proximal Doped Silicon ATR Crystal Working Electrodes

“…ATR-IR-SEC has been employed to probe chemical processes occurring in solution above the IRE, such as the investigation of redox chemistry, CO 2 R catalysis, and polymerization. ,,,− It is commonly used in one of three configurations as categorized by Odijk and co-workers: (i) the deposition of an IR transparent material ( e.g. , a thick gold mesh or a thin boron-doped diamond (BDD) film), onto the surface of the IRE that acts as a working electrode (WE); ,− , (ii) the deposition of a very thin metal layer as the WE on the IRE; ,,,,,,,− or (iii) the use of a thin porous spacer ( e.g. , a Nafion membrane or carbon nanoparticles/fibers), between the IRE and a WE ( e.g.…”

In Situ ATR-IR Observation of the Electrochemical Oxidation of a Polycrystalline Boron-Doped Diamond Electrode in Acidic Solutions

“…Infrared (IR) spectroscopy can obtain information at the solid–liquid interface sensitively, and this has been applied to studies on electrochemistry. , Recently, the IR measurements of electro-polymerization and solution species on BDD electrode were performed using the attenuated total reflection (ATR) method. , However, detailed assignment of surface species during electrochemical oxidation on BDD is unclear. In this study, we reveal oxidative species of a polycrystalline BDD electrode using in situ ATR-IR spectroscopy.…”

Low-Temperature Dielectric Spectroscopy Characterization of the Oxidative Degradation of Lubricating Oil

“…As a rapid, automated, and high-throughput quantitative analysis tool, FT-IR presents characteristic infrared absorption peaks associated with the oxidation, nitration, and sulfation products during the oxidative degradation of lubricating oil, , which is consistent with the issued standard test methods as ASTM D7414, D7624, and D7415, respectively. These characteristic spectra peaks were often used to monitor the trends of oxidative degradation, including the determination of TAN and TBN in oil. − A quantitative model was developed by Dong et al between the characteristic absorption of carboxylic acid and TAN. Three mathematical models were established by Adams et al to qualitatively and quantitatively predict TAN and antioxidant concentration, viz, principal component analysis (PCA), partial least-squares (PLS), and two-dimensional (2D) FT-IR correlation spectroscopy.…”

“…Three mathematical models were established by Adams et al to qualitatively and quantitatively predict TAN and antioxidant concentration, viz, principal component analysis (PCA), partial least-squares (PLS), and two-dimensional (2D) FT-IR correlation spectroscopy. An in-site investigation by attenuated total reflectance was carried out by Purushothaman et al into the depletion of detergents and antiwear agents during oxidative degradation. According to Guan et al, , the appearance of characteristic 1774 cm –1 carboxyl absorption for seriously degraded oil was most likely due to the formation and accumulation of highly oxidized polar products.…”