Calorimetric effects and temperature dependence of simple ion adsorption at oxide/electrolyte interfaces: The systems in which PZC and CIP do not coincide

The temperature dependence of surface charge isotherms in the system where PZC and CIP do not coincide was subjected to a quantitative theoretical-num erical analysis. That analysis, based on the TLM model of the oxide/electro lyte interface, and on the assumption of the 2-pK charging mechanism, would suggest that the relation (pK(a1)(int) + pK(a2)(int))/2 = PZC may no longe r be preserved in this system. However, the existence of CIP may still be u sed to develop interrelations between equilibrium constants of various surf ace reactions, The observed linear relationship between CIP and electrolyte concentration is very useful in estimation of these constants, Also, linea r dependences of PZC and pH(CIP) on 1/T were found. Their theoretical-numer ical analysis leads to the conclusion that in this system no enthalpic effe cts accompany the attachment of the anion to the doubly protonated surface oxygen, and the adsorption of cation on the empty surface oxygen. (C) 2000 Academic Press.