Can i go to negative potential window?

I think you can go to negative potential window in three electrode setup to investigate the behavior of material. I don't understand the meaning of negative operating "VOLTAGE" of a device. Following the paper which you have mentioned "JMCA" they have performed the experiment in potential window of -1.0 to 1.0 V vs. Ag/AgCl in 1 M aqueous H2SO4, which is three electrode assembly. In this setup it is incorrect to put as Voltage in X-axis as is labeled for figure 4 (a), (b) and (c). And also in the CV and CD of device has the similar problem.

Also regarding acs nano paper, Y-axis of figure 6 (b) and inset of figure 6 (d) are labeled as potential and potential (V vs Hg/HgO) respectively which is indicating the measurement was done in three electrode setup. However, in the caption for those figure saying the measurement is done for device which makes result ambiguous. 

We perform the measurement in three electrode system to understand how the material is behaving in lower and higher potential range with respect to “reference electrode”. When we do the measurement of device either for symmetric or asymmetric device we short counter and reference electrode and then we complete the circuit. In this setup the material which was showing response in negative potential range with respect to reference electrode will show its property towards lower voltage range (starts from zero) and the material which was showing behaviour in higher potential range with respect to “reference electrode” will show its contribution at higher voltage (away from zero). Below are some links which could be useful to you.    

http://www.sciencedirect.com/science/article/pii/S0008622310005531

DOI: 10.1149/2.023204esl

http://www.sciencedirect.com/science/article/pii/S1388248110002948

http://www.sciencedirect.com/science/article/pii/S138824811500209X

Can i go to negative potential window?

I think you can go to negative potential window in three electrode setup to investigate the behavior of material. I don't understand the meaning of negative operating "VOLTAGE" of a device. Following the paper which you have mentioned "JMCA" they have performed the experiment in potential window of -1.0 to 1.0 V vs. Ag/AgCl in 1 M aqueous H2SO4, which is three electrode assembly. In this setup it is incorrect to put as Voltage in X-axis as is labeled for figure 4 (a), (b) and (c). And also in the CV and CD of device has the similar problem.

Also regarding acs nano paper, Y-axis of figure 6 (b) and inset of figure 6 (d) are labeled as potential and potential (V vs Hg/HgO) respectively which is indicating the measurement was done in three electrode setup. However, in the caption for those figure saying the measurement is done for device which makes result ambiguous. 

We perform the measurement in three electrode system to understand how the material is behaving in lower and higher potential range with respect to “reference electrode”. When we do the measurement of device either for symmetric or asymmetric device we short counter and reference electrode and then we complete the circuit. In this setup the material which was showing response in negative potential range with respect to reference electrode will show its property towards lower voltage range (starts from zero) and the material which was showing behaviour in higher potential range with respect to “reference electrode” will show its contribution at higher voltage (away from zero). Below are some links which could be useful to you.    

http://www.sciencedirect.com/science/article/pii/S0008622310005531

DOI: 10.1149/2.023204esl

http://www.sciencedirect.com/science/article/pii/S1388248110002948

http://www.sciencedirect.com/science/article/pii/S138824811500209X

Kush thanks for the answer. If my material is showing pseudopeak -0.3to 0 in three electrode w.r.t. SCE then is should show pseudopeak after zero in two electrode symmetric supercapacitor thats what you mean to say?

Is there any differenc between potential and voltage in case of device?

Debarati, there is no any meaning of pseudo-peak. If there is peak then it is redox peak because of reaction in that potential range. You can look on the links below for having better understanding. In two electrode system the electrochemical nature could change (may be you can see different nature) from three electrode system. In case of device Voltage is appropriate term to use. 

http://science.sciencemag.org/content/343/6176/1210.full

Kush thanks for the papers . its very helpful. I am reading it.

I still have a doubt. should i always start from 0 for the two electrode wheather symmetric or assymetric supercapacitor because the device gets discharged at 0V.

but then why they are scanning it in the negative range (-0.8V) and how it is justified in the attached paper.please reply

I think Kush has explained it well and you are asking the same question again. In both papers you attached, the CV measurements are in 3 electrode set-up where they are applying +ve and -ve potentials with respect to reference. In two electrode device there is no reference electrode hence applying -ve potential does not make any sense.  You can consider our recent paper, We have tested Ag:BiVO4 in 3 electrode set-up from -0.6 V to +1 V with respect to Ag/AgCl so the total potential difference is around 1.6 V. When you make 2 electrode cell this difference gets divided equally (not all times) across both electrodes and the symmetric device shows total voltage of 1.6 V.

Overall, you can make conclusion that, in symmetric and asymmetric cells you need to start from 0 V.  

You can follow our papers as well few papers I have attached for you to better understand the concept.

Thanks a lot deepak. I understood that i have to start scanning from 0.Thanks a lot for your help.

For a two terminal device which a negative and a positive electrodes (as a standard supercapacitor you can buy from a company) you can only scan from 0V to positive voltage. Otherwxise it is like you are trying to reverse the electrode polarity which can be dangerous and detrimental to the safety of the device.

Hope this help

Cheers

Thanks Muhammad.

Thanks Prof Thierry Brusse. It really helped me.