Parsons Drew F, Salis Andrea
College of Science, Health, Engineering & Education, Murdoch University, 90 South St., Murdoch, WA 6150, Australia.
Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, S.S. 554 bivio Sestu, 09042 Monserrato, CA, Italy.
J Chem Phys. 2019 Jul 14;151(2):024701. doi: 10.1063/1.5096237.
We resolve a thermodynamic inconsistency in previous theoretical descriptions of the free energy of chemisorption (charge regulation) under conditions where nonelectrostatic physisorption is included, as applied to surface forces and particle-particle interactions. We clarify the role of nonelectrostatic ion physisorption energies and show that a term previously thought to represent physisorbed ion concentrations (activities) should instead be interpreted as a "partial ion activity" based solely on the electrostatic physisorption energy and bulk concentration, or alternatively on the nonelectrostatic physisorption energy and surface concentration. Second, the chemisorption energy must be understood as the change in chemical potential after subtracting the electrostatic energy, not subtracting the physisorption energy. Consequently, a previously reported specific ion nonelectrostatic physisorption contribution to the chemisorption free energy is annulled. We also report a correction to the calculation of surface charge. The distinction in "partial ion activity" evaluated from bulk concentration or from surface concentration opens a way to study nonequilibrium forces where chemisorption is in equilibrium with physisorbed ions but not in equilibrium with bulk ions, e.g., by a jump in ion concentrations.
我们解决了先前在包含非静电物理吸附的条件下，应用于表面力和颗粒间相互作用的化学吸附（电荷调节）自由能理论描述中的一个热力学不一致问题。我们阐明了非静电离子物理吸附能的作用，并表明一个先前被认为代表物理吸附离子浓度（活度）的项，应改为仅基于静电物理吸附能和本体浓度，或者基于非静电物理吸附能和表面浓度来解释为“部分离子活度”。其次，化学吸附能必须理解为减去静电能后的化学势变化，而不是减去物理吸附能后的变化。因此，先前报道的特定离子对化学吸附自由能的非静电物理吸附贡献被取消。我们还报告了对表面电荷计算的修正。从本体浓度或表面浓度评估的“部分离子活度”的差异，为研究非平衡力开辟了一条途径，在这种情况下，化学吸附与物理吸附离子处于平衡，但与本体离子不处于平衡，例如通过离子浓度的跃变。
