# Is the Hybrid sulfur cycle a good way of making hydrogen and oxygen on Venus?

Assuming we collect Sulfuric acid from Venus clouds using some sort of airship, what would be the best way of turning this into hydrogen and oxygen? I came across something called the Hybrid sulfur cycle which goes like this:

H2SO4(aq) → H2O(g) + SO2(g) + ½ O2(g) (thermochemical, T > 800 °C)
SO2(aq) + 2 H2O(l) → H2SO4(aq) + H2(g) (electrochemical, T = 80-120 °C)


Are there better ways than this? I assume you can also somehow exploit the fact that it is quite hot on Venus to get the temperature required for the reaction. Like go down to a level with say 200 degrees and use a heat-pump to increase the temperature further. I have no idea if that works for high temperatures.

The assumption here is that both hydrogen and oxygen are useful chemical for long term survival. I will assume the electrochemical energy will likely come from solar cells, as Venus has quite a lot of sun. But I was wondering if the process could be made more efficient by utilizing the high temperature already existing on Venus. Planetary surface is probably unlikely as the pressure is too high, so it would be at a higher altitude.

• I'm just curious what an airship will do with the hydrogen and oxygen. I'm wondering if the electrochemical step require (in reality) more power (electrical) than could ever recovered propulsively by burning the two gases. Are you thinking of a fuel cell as a 'battery'? I found this and this. – uhoh Aug 9 '16 at 1:57
• @uhoh no, I don't see this as a net-energy production. I'll update the question. – Erik Engheim Aug 9 '16 at 13:52
• Great, thanks! When you say "..both hydrogen and oxygen are useful chemical for long term survival." do you mean survival of humans on venus or do you mean survival of one or more spacecraft/lander/rover on the surface? – uhoh Aug 9 '16 at 14:09
• By humans. I imagine hydrogen could be used with CO2 together with the sabatier reaction to produce methane e.g. which is fairly practical to store for later energy production. Alternatively making ethylene. With CO2+H2 you got all in principle for making a lot different forms of artificial polymers. Could be useful for expanding a habitat. – Erik Engheim Aug 11 '16 at 7:11
• You could also ask about the chemistry part in chemistry stackexchange (if you haven't already) - temperatures, catalysts and their degradation, byproducts that could slow down the reaction, etc. and then bring some of that info back here for a more "space exploration" perspective - issues about the plane, atmosphere, keeping people alive on the surface, etc. I like you question a lot! – uhoh Aug 11 '16 at 10:38

The atmosphere of Venus is about 30 ppm $H_2O$ and about 1 to 2.5 ppm $H_2SO_4$. (According to Planetary Sciences 2nd ed. by De Pater & Lissauer, 2010, p. 88.)