Howdy Devina,

It is possible to reduce CO2 to methane, using nickel as a catalyst at a temperature of more than 360 °C and a stoichiometric flow of CO2 and hydrogen gas in the reactor. You get very close to a 100% conversion efficiency. Of course, to get at 360 °C one needs a lot of electric energy, and that's costly since a lot of energy is needed to get to 360 °C and to get this highly endothermic reaction going. Hence, you require a cheap source of electricity (and hydrogen) , to produce methane from CO2.

However, to produce hydrogen from CO2 looks queer. Maybe KOH is dissociated? Unless you use another source of hydrogen, like the carbon catalyst?

Traditionally, CO can be produced when you have incomplete combustion, like combustion with a stoichiometric lack of oxygen, of coal or wood. Check the composition of your carbon catalyst before and after the reaction has taken place, maybe it is combusted a well?

I agree with Frank Veroustraete.

Hi Devina,

I'd suggest to have a close look on your outlet flow from the reactor: do you use a flow meter to record its value (and then subsequently use this value for your FE calculations)? Also, if you produce a lot of hydrogen, flow meter calibration might be no longer valid.

In general, it is possible to get high FE for H2 from CO2R, in case when the reaction conditions/catalyst do not allow for contact of CO2 with catalyst; however anything higher than 100% suggest an experimental error.

Hope it helps.

Best,

Magda

Dear Frank Veroustraete ,

Thank you very much for your kind answer and insight regarding CO2 reduction to methane. It is indeed an interesting way of reducing CO2 using renewable energy source such as hydrogen powered fuel cell, or the others.

However, I'm afraid that my experiment didn't involve combustion or elevated temperature, since I use electrolysis to reduce the CO2 on the pre-synthesized carbon catalyst. In this field of research, which is CO2 electrochemical reduction, Hydrogen is often produced as the byproduct from the competing reaction, Hydrogen Evolution Reaction (HER) which occured to be spontaneous at near 0 V overpotential.

Nevertheless, thank you very much for your kind responds.

Regards,

Devina

Hello Magda H. Barecka ,

Thank you for your valuable suggestions!

I'm currently encountering issues related to the gas flow at the reactor outlet, since it often fluctuated and I had hard times to precisely fix the gas flow rate in the FE calculation.

Thanks for pointing out the problems, I really appreciate it.

Regards,

Devina

This is impossible. Something wrong in your calibrations/calculations.