Chemistry at interfaces: adsorption/desorption equilibria, heterogeneous catalysis, self-assembled monolayers, surface reconstruction. Central to industrial catalysis (Haber–Bosch, Fischer–Tropsch, auto catalysts) and electrochemistry.
surface-chemistry
Langmuir adsorption isotherm
Fractional surface coverage θ vs. partial pressure p of an adsorbate on a homogeneous surface with non-interacting sites: θ = Kp / (1 +…
Langmuir adsorption model
Microscopic picture underlying the Langmuir isotherm: adsorption is a reversible reaction A(gas) + site(surface) ⇌ A·site with a single…
BET isotherm
Brunauer–Emmett–Teller multilayer extension of the Langmuir model: allows adsorbate molecules to stack into multiple layers, with the first…
Physisorption vs. chemisorption
Two regimes of molecular adsorption. Physisorption: driven by van der Waals forces; ΔH_ads ≲ 40 kJ mol⁻¹; multilayer possible; reversible;…
Heterogeneous catalysis
Catalysis in which the catalyst and the reactants are in different phases — typically a solid catalyst acting on gas- or liquid-phase…
Sabatier principle
Optimal catalyst binds intermediate with moderate strength — too weak: no activation; too strong: poisoning. Volcano plots of activity vs…
Scaling relations (computational catalysis)
Binding energies of related adsorbates (e.g., CHx, OHx) linearly correlate across transition-metal surfaces. Limits independent…
Single-atom catalysts
Isolated metal atoms on oxide/carbon support; maximize atom efficiency + uniform active sites. Pt₁/FeOₓ for CO oxidation (Zhang 2011).…
XPS (X-ray photoelectron spectroscopy)
Surface-sensitive (~5 nm) elemental + oxidation-state analysis via photoemission KE. Binding-energy shifts diagnostic of chemical…
Sum-frequency generation (SFG) spectroscopy
Second-order nonlinear optical probe selective to interfaces (χ⁽²⁾ vanishes in centrosymmetric bulk). Vibrational spectra of buried…
Gibbs adsorption isotherm
Γ = -(1/RT)(dγ/d ln a); surface excess vs activity; surfactant CMC determination.
Young–Dupré equation & wetting
γ_SV = γ_SL + γ_LV cos θ; θ contact angle; hydrophobic/hydrophilic; lotus-effect super-hydrophobicity.
Microkinetic modelling of catalysis
Elementary-step rate equations with DFT energies; degree of rate control (Campbell); volcano plots (Sabatier).
Surface reconstruction
Minimize energy via rearrangement: Si(111) 7×7, Au(110) 1×2; detected by LEED, STM.
Self-assembled monolayers (SAMs)
Alkanethiol on Au(111) √3×√3 R30° lattice; functionalization of surfaces; molecular electronics, patterning.
Langmuir–Blodgett films
Monolayer of amphiphiles on water, compressed and transferred onto solid; π–A isotherms; multilayer architectures.
Sum-frequency generation (SFG)
χ² process forbidden in centrosymmetric bulk → surface selective; vibrational SFG identifies interfacial species.
STM & AFM imaging
Atomic-resolution tunneling (STM) and force (AFM) imaging; manipulation of individual atoms; Binnig–Rohrer 1986 Nobel.
Heterogeneous catalytic cycles
Adsorption, surface reaction, desorption; Langmuir-Hinshelwood vs Eley-Rideal; Mars-van Krevelen for redox oxides.