Self-Constructing Kinetic Rate Equation from Experimental Rate Data Points of Heterogeneous Adsorption of Thiophenol on Gold Substrates Using Surface Enhanced Raman Spectroscopy
Abstract
Traditional practices in kinetics start with a proposed mechanism and then derive a rate model (equation), which is tested with experimental data profiles. A new approach was used to self-construct a unique, single surface-enhanced Raman spectroscopy (SERS) kinetic rate model that fits all 25 experimental rate profiles (at different temperature and pH values) without prior mechanisms, user input bias, default parameters, or rate model assumptions. The 25 experimental thiophenol (TP) adsorption data profiles on gold metal surfaces (SERS signal vs time) at four pH values and six temperatures were collected using SERS. TP adsorption rate profiles show a variety of results from a simple exponential to S-shaped rate profiles. The new SERS kinetic rate model reveals that TP adsorption has a (nearly constant) low temperature of activation (Ta = Ea/R = 3000 K) at <-pH 6. The Ta increased by 900 K to reach 3900 K under a high pH of 10. The Ta value of 3000 K was consistent with the literature for the AuS adsorption bond. The increase in Ta by 900 K (i.e., 3000 to 3900 K) was consistent with the difference due to pH changes corresponding to the protonation state.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2019
- Accession Number
- AD1074278
Entities
People
- Ashish Tripathi
- Erik Emmons
- Jason A Guicheteau
- Richard Vanderbeek
- Waleed Maswadeh