Notarial services are for all nationalities and are by appointment only. Normally the document to be notarized is for use within the United States, although there may be exceptions. If you have multiple documents to be notarized, you should only make one appointment. You will pay $50 USD, at the Embassy or Consulate on your day of appointment, for each notary seal required.
On the day of your appointment, you must:
DS-3053: To notarize a DS-3053 Statement of Consent: Issuance of a U.S. Passport To a Minor Under Age 16 (PDF, 345K), please review the instructions listed on the form, the information fields that must be completed, and bring your original, valid, government-issued photo ID as well as a photocopy of both sides. As the U.S. Department of State requires that this form be notarized, this service is performed free of charge.
Power of Attorney (in conjunction with U.S. passport applications): When both parents are unable to be personally present to apply for a minor’s U.S. passport, and they wish to designate a third party to do so, they may sign a power of attorney (POA) before a notary public. This POA must contain specific data fields; see a sample. Note that photocopies of both sides of each parents’ original, valid, government-issued photo ID must be included with the POA. As the U.S. Department of State requires that this form be notarized, this service is performed free of charge.
At the Direct Request of a U.S. Municipal, State or Federal Entity
At the Direct Request of a Foreign Government
More information can be found here: https://www.ecfr.gov/cgi-bin/retrieveECFR?n=pt22.1.22#se22.1.22_11.