[Shadsu (OP)]

HI, I'm new around.

 I'm trying to experiment just for fun, I forgot a lot from old chemistry lessons.

My questions is:

I have salty water which I perform electrolysis on using gold anode and copper cathode.
From what I know when all sodium chloride has reduced i have gold chlorid and sodium hydroxide

Are only these two substances created?
Have all gold ions reacted with chlore? No one is migrated to cathode, plating it ?
Have all sodium ions reacted with hydrogen?

magnetic mixing during electrolysis, could be important for the creation of more or less gold chloride and sodium hydroxide?

Sorry for all the questions.
Best regards Paul

[chiralSPO]

The pH and voltage between the electrodes is very important. It is easier to oxidize chloride to chlorine (in acid) or hypochlorite (in base) than it is to oxidize gold to chloroaurate ions in the presence of chloride, so that is likely the primary reaction happening at the anode.

Also note that "anode" and "cathode" are actually ambiguous because it depends whether we are considering the electrochemical cell as the system of interest or the circuit between the electrodes as the system of interest. I assume that you mean that electrons are flowing from the gold electrode, through the circuit to the copper electrode?

[Bored chemist]

Wet chlorine will oxidise gold.

The rate will be dependent on things like concentration and temperature (as well as the presence of other ions like chloride)

[Shadsu (OP)]

Thanks to both for your answers, chiralSPO and bored chemist.

I used:
250 ml distilled water
120 mg sodium chloride
30 volt and approximately 350 ma current for 40 minutes, I think
Gold anode was 1 cm far from copper cathode. Electrones flow to copper electrode, from gold electrode.
Temperature is room temperature.

In this situation will I have only gold chloride and sodium hydroxide?

The positive gold iones will themselves surely link with chlorine or many of them will plate the copper cathode?

If the temperature would be 80 C, what does it change exactly ? Will I have different substances? The gold chloride and sodium hydroxide form themselves quicklier?

Mix with a magnetic stirrer could in some way change something ?

Thanks in advance for helping me

[chiralSPO]

30 V is really high for a single electrochemical cell! At these potentials you're likely going to see many different competing reactions:
• Oxidation of Cl^– to Cl₂ or ClO^– (which I now know can then react with gold metal in water--though if the chlorine gas leaves solution before reacting with gold, it won't be much use...) or even up to ClO₃^– and/or ClO₄^–
• Oxidation of water to oxygen gas or hydrogen peroxide (which will then decompose into oxygen gas)

I suspect you would have better luck using a more conductive electrolyte. Maybe try bumping up the concentration of salt by a factor of 10 (1.2 g per 250 mL). Then see what voltage you need to get the same current--I doubt you need more than 4 V to force the electrochemical reactions to occur, and the rest is just to overcome the resistivity of the solution.

If your goal is to isolate gold chloride (or chloroauric acid), you might have better luck using hydrochloric acid as your electrolyte--Even low concentrations of HCl are very conductive, and increasing the concentration of H⁺ ions means that hydrogen generation will be very fast at the copper electrode (outcompeting gold reduction). Finally, you can evaporate or boil off all of the remaining acid (carefully!), rather than trying to separate from NaCl and NaOH, (and possibly NaOCl, NaClO₃ and/or NaClO₄).

Stirring likely won't have much effect at these currents and electrode separation (trying to run high current with large electrode separation is made easier when there is mixing--otherwise current is diffusion limited)

Room temp is probably best--increasing the temperature will make it much easier to drive off chlorine gas and oxygen gas (which you don't want), and will only marginally facilitate gold dissolution.

[Bored chemist]

At 30 volts most of the energy is going into heating the solution.
You should use bigger electrodes, closer together an a much higher concentration of salt.

[Shadsu (OP)]

My Target is try to produce gold nanoparticles of different sizes using different reducing agent, with the electrochemical method and not turkevich method.

I prefer to use salt as electrolyte and not other form of chloride because of sodium, I think it will help to avoid gold ions moving to copper cathode, binding them to chloride.

I think an increase of salt is not usefull because when I will reduce gold chloride, if the gold particle concentration is too high, the particles will form too big clusters.
My target is a 40 ppm concentration of particles.

Relative to voltage I thought it must be better to produce gold chloride...is it not so in your opinion?
When possible my target is have in soLuton only gold chloride and sodium hydroxide.
Which are the better electrolysis parameters?

[Shekhar shah]

Exactly what happens depends on what electrolyte salt is used in the water. There must be an electrolyte in solution with water for current to flow.

The first electrolysis experiment I ever did at home as a 9-year old was with bare copper wires for electrodes, a battery, and sodium chloride (NaCl) as the electrolyte. The bubbles for H2 and O2 formed and fizzed off of the electrodes immediately, as expected, and I was thrilled. Within a minute or so, however, the electrodes themselves began to change.

Source:-[COMMERCIAL LINK REMOVED]