Carbon dioxide electrochemical reduction is a very vast field of research..you should read papers about it to get a more complete information on the subject, that way you could see the importance of such methods

Augusto Rodríguez I read but can't explain the voltammogram . Can you explain please?

Hello,

I do research in CO2 electrochemical reduction. LSV and CV give you similar info, you can estimate the catalytic rate if you do them under CO2 and also under inert gas (N2 or Ar) and compare the currents.

Chronoamperometry isn't something that is commonly used, but we do "bulk electrolysis" where you hold the potential and measure the current over time. From this and the amount of CO or formic acid made, you can get faradaic yield (basically %yield of CO2 reduction products based electrons put in).

I study homogenous electrocatalysts so we also use in-situ spectroelectrochemistry (like IR-SEC) to study the species involved in catalysis.

For product analysis what voltammetric mathod should i apply?

Nazifa,

After you do LSV/CV analysis you will know the potentials that the reaction starts. Hold the voltage more negative than that using bulk electrolysis for some set time (such as 30 min or 1 h) and then sample the headspace and solution and analyze for products. Check out papers similar to what you want to do to see what voltages and times, etc they used. The size of your working electrode will affect your current and the total coulombs passed.

Thank you so much dear Kyle A. Grice . Should there be any peak in LSV or CV ? Do i need to bubble CO2 gas into electrolyte during electrolysis? what should be the pH then?

Hello Nazifa,

Yes you will need to bubble in CO2 at the beginning, both to have CO2 in there and to purge out an O2 (most CO2 reduction systems can do O2 reduction too so you want to not have air in there when doing any e-chem. If you want to examine the CV or LSV without CO2, bubble in N2 or Ar). You don't need to bubble it during electrolysis, although some people have tried that (with flow cells and such).

As for pH, it will become more acidic as CO2 is bubbled in, so check it's pH after you bubble CO2. pH will certainly have an effect on catalysis (too acidic and you might just do proton reduction, another common reduction process with similar potentials to CO2 reduction). You can use a buffer like bicarbonate to keep the pH steady-ish. Definitely look up and read relevant papers. A google scholar search is always a good idea:

https://scholar.google.es/scholar?q=pH+effects+on+CO2+reduction+electrode&hl=en&as_sdt=0&as_vis=1&oi=scholart

Think carefully about how you will detect and quantify products. You will want to make calibration curves for CO and H2 using gas chromatography if you want to detect them. Formate in solution can be detected with NMR or ion chromatography (I've used NMR, but not ion chromatography to do this, but I've seen literature that uses ion chromatography). Depending on the electrode you can make other products (for example, Cu can make ethylene and other products).

Good luck on your CO2 reduction chemistry!

-Kyle

Kyle A. Grice Thank you so much. For product analysis do i need separator ? what if i do this in one compartment with three electrode system without separator ?

Not sure what you mean for a separator. As long as you have a septum you can sample the headspace with a gas-tight needle. You will need a Gas Chromatograph with the correct column and such for detecting H2, CO, and other gasses. It's good practice to make the calibration curve with your electrolysis system set up exactly as how it is set up for running electolysis. You can inject known amounts of the gasses into the headspace and then sample the headspace.

You have to remove liquid to sample the solution for products like formate.

Kyle A. Grice In a typical people commonly use H type cell with Nafion separator. I wanted to know if do electrolysis in one compartment without any separator ? will there be any issue?

Linear sweep voltammetry can be used to determine the current density of electrocatalyst, Cyclic voltammetry is typically employed to measure the electrochemically active surface area, and Chronoamperometry is utilized to determine the stability of electrocatalyst during CO2RR and yield of a certain product, produced during electrochemical CO2 reduction.

In a typical H-type cell, you must use Nafion 117 Membrane to separate the anodic and cathodic section. Otherwise, the reactants and products will get mixed with each other and it will be difficult the assess them.

Azeem Mustafa thank you so much. Can you tell me by which method you mentioned above tafel slop can be calculated?