Yes baking soda can be used to treat diaper rash.
Just mix some baking soda with some water to make a baking soda and water paste and then apply the baking soda paste to the diaper rash.
The baking soda will naturally get rid of the diaper rash over a few days to a week.
You can also apply some apple cider vinegar to the diaper rash which will also help heal the diaper rash.
I also recommend letting your toddler or baby go without a diaper for 30 minutes or an hour per day to help the diaper rash heal and give the diaper area some air.
Apply some diaper rash cream to the diaper area as well whenever changing diapers to keep the moisture away from the babies skin.
Also make sure to change diapers often and do not let the baby or toddler stay in a wet diaper for too long to prevent diaper rash.