Dear Anafi Nuraini

I will tell you how we do the ink preparation in our lab almost similar to you:

5 mg of catalyst in 5 ml DI water and 10 ml IPA and 10 micro-liter of Nafion then sonicate for 30 minutes. Ink drop casted on RDE and keep it for 2-3 h in room temperature for drying.

"Current keeps dropping during CV measurement" is mainly due to your materials instability during cycling.

You may try some commercials catalyst for OER and see the how I-V curve looks.

Best Regards,

Bapi

Dear Anafi Nuraini

Firstly you have to be sure that your powder is containing uniform and small particles as much as you can. If you you have a homogenous dispersion after preparing your ink that's mean the ink isn't the problem. However, after dropping your solution on the electrode surface I suggest you to let it dry at room temperature. From some materials such as (phosphides nitrides and oxides ) during electrocatalysis especially for OER , there are a CV activation (For instance 500 cycles ) should take it time to have a stable and good result .

Good luck

i think your catalyst get dissolving into the electrolyte. please check stability of your catalyst in the electrolyte.

My sample is Ir-Ni nanowires. This material is hardly stable. After I sonicate using bath sonication and horn sonication, the Ir-Ni ink will make sediment within a couple of minutes. Also, I think my ink is quite watery.

Any suggestion?

I use RDE Au (d=3 mm). Is it proper enough?

Thank you.

can you please share your graph here?

Venkateswara Raju Chikkili Here I attach the graph . I scan from 0.9-1.5 V vs SCE. Scan speed 100 mV/s for 20 cycles.

After this preconditioning CV, I scan with a slower speed (20 mV/s for 1 cycle).

Thank you

I think this data is fine. every system shows slight decrease in current during cycling. if you have sudden decrease with maximum loss in current should be worried. But your case not sudden decrease in current. So, it is fine. you please compare the current density and onset potential of your catalyst with reference (RuO2). If you are interested repeat the same with 5 mV/s scan rate.

Thank you very much Venkateswara Raju Chikkili

Did you mean 5mV/s scan rate for 20 cycles? or 5mV/s after conditioning?

I think the scan rate 100 mV s-1 is a little high for stabilizing the sample before starting the actual measurements. Try at little lower scan rates like 20-30 mV s-1 for about 100 CV cycles. For ink preparation, the powder sample should be ground finely before sonicating with the other components. After coating, it is better to dry at room temperature for about 10-12 h.

Thank you, Dr. Thangjam Ibomcha Singh for your very nice advice. Let me try it.