The iPhone 11 is a 5v2a charger.
Apple 11 can use 5v2a charger, but there is no way to achieve fast charging, fast charging then need to support pd charging protocol, and charging power to reach 20 watts, usually 9 volts 2:22 amps like this, the charger can only give it slow charging, full charge may be up to two hours or so, because Apple has a charge protection chip, It's not gonna break the phone.
It can be used because during the charging process of the mobile phone, the system will automatically identify and detect the charging current and voltage to protect the battery.