Notes from 7/7/20

Bintao training on temperature-dependent RuO2 CV

Step 0: Calibrate the temperature of the water

• Using temperature probe (connected to the back of water temp controller), check the temperature in the cell electrolyte is at the expected temperature

1. Cleaning the temperature dependent cell

• Night before experiment, soak cell overnight in LiOH (15-20 pellets)
• On experiment day, heat the cell until the electrolyte boils; then dispose of the LiOH
• Wash your gloves in DI water to get rid of the powder on the gloves
  • Wash the cell many times in DI water
  • Wash the cell stoppers in DI water

2. Preparing the 0.1 M LiOH solution
   • As you prepare the solution, plug the cell with the stoppers
   • Pour in the measured LiOH powder into the inner cell; pour in the measured DI water into the inner cell
   • Cover the graduated cylinder used to measure the water with parafilm after using
3. Purge the cell in Ar
   • Wash the RuO2 working electrode, Ag/AgCl reference electrode, the Pt counter electrode, and purging tube with DI water before inserting into the cell
     • Note that RuO2 WE is inserted in the largest cell hole with the large stopper
   • Purge the cell with Ar for 15 min
4. Take the CV of RuO2 using small potential window (parameters below)

• • CV doesn’t look clean (not symmetrical about 0 current) – resolved by cleaning RuO2 in DI water more
    • For more intense cleaning, you can let the RuO2 sit in 0.1 KOH for 15 min

5. Calibrate to RHE – purge with H2 to see potential difference between RHE and Ag/AgCl (not done today)
6. Set temperature of cell to 5 deg C
   • Water temp controller has two black tubes
     • Tube with teal tape = water out, inserted into lower cell tube hole
     • Second tube = water in, inserted into the upper cell tube hole

• Set the water temp controller to 5 deg C using the middle button “T” and then press “OK”, water will flow into outer jacket of the cell

• Now wait for 45 min – 1 hour for the cell to cool down
• Take out the RuO2, wash it in DI, and soak it in DI
  • When you’re ready to insert the RuO2 back into the cell, wash it under DI and dry with N2 gas

7. RuO2 CV in Ar purge
   • Purge the cell with Ar and use same CV parameters as above
8. OER CV (parameters below)
   • Want the adsorption peaks to be << OER peak

9. Impedance measurement
   • Use the value resistance value at the intersection of the semicircle and exponential for the Rs value

10. In preparation for high-temp experiments prepare and pipette 1 M NaOH solution for the Hg/HgO electrode