# Photodecomposition of Anode/Cathode

1. May 31, 2013

### citw

Can some one explain (to a non-chemist) what exactly is happening in the decomposition reactions

$$\text{MX}+zh^++\text{solv}\longrightarrow\text{M}^{z+}\cdot\text{solv}+\text{X}\text{ (oxidation) }$$

and

$$\text{MX}+ze^-+\text{solv}\longrightarrow\text{M}+\text{X}^{z-}\cdot\text{solv} \text{ (reduction) }$$

In these reactions, MX referers to a compound semiconductor (e.g., M= Zn, Ga, Ti, etc., X=S, N, O2, etc.). It's my understanding that the first equation describes the oxidation of the semiconductor by its photogenerated holes, while the second describes the reduction by photogenerated electrons. This can be found in the following article

http://pubs.acs.org/doi/abs/10.1021/cm302533s

However, as I have limited education in chemistry, I don't really understand what is meant by the terms such as z in front of the electron, or "solv" indicated with the oxidized/reduced products. Are we saying "z electrons/holes", therefore changing the oxidation state by this amount? The "solv" part I really don't know about.

2. May 31, 2013

### Staff: Mentor

z is just a small integer number, solv means solvent/solvated.

3. May 31, 2013

### citw

So is it like I was saying, "z" electrons/holes?

What does it mean that "solv" appears as an individual reactant but is indicated next to (as?) one of the products?

4. May 31, 2013

### Staff: Mentor

Yes.

The way I read it you don't know how many molecules of solvent are used to solvate the ion, and it is not that important. What is important is that the reaction takes place in solvent and its molecules do solvate the produced ion.

It is not a standard notation, just a handy shortcut.