Modeling photoelectrochemical reactions in aqueous medium with GWB

[Alero]

Hello,

Is it possible to generate geochemical models of photoelectrochemical reactions in an aqueous system using GWB? A typical chemical equation for one reaction is:

Cl^- + 4H₂O + 8h⁺ = ClO₄^- + 8H⁺

where h⁺ = positively charged hole (not proton (H⁺)) generated upon the illumination of a semiconducting mineral

I have tried to modify the thermo database (add h⁺ as a  new species, copy and modify the electron panel) but I end up with charge or reaction imbalance when I run the model - one reason being that h⁺ does not have a mass.  Also, apart from chloride and perchlorate, the reactions I am considering include other oxychlorine species like chlorite and chlorate.

Alero Gure

Edited April 17, 2018 by Alero
Previous reaction was not balanced

[Brian Farrell]

Hi Alero,

The software does not currently support photoelectrochemical reactions like that you've described.

Regards,

Brian Farrell
Aqueous Solutions LLC

[Brian Farrell]

Hi Alero, 

After thinking about this some more, you might be able to put together something like you described with a modified thermo dataset. I'd start by adding h+ as a redox couple, using the reaction h+ = H+ + .25 O2(aq) - .5 H2O. Set the charge of h+ to 1, its mass to that of an electron, and make it really unstable. In React, set up the chloride oxidation problem with a kinetic rate law. Decouple the h+ as well as the ClO4-, set very small initial amounts of h+ and ClO4-, then enter the reaction above for the kinetic redox reaction and assume a rate constant. If you add the h+ as a simple reactant, you should observe the Cl- oxidizing to ClO4- and pH decreasing with time, like in the reaction you described.

Hope this helps,

Brian