It might work, but would be very slow. You would be better off with a 3rd party charger that delivered more power. Like the Mac Charger or the 3rd party charger.
USB-C Power Delivery allows the charger and device to verify that the supply can provide power at voltage and current that is acceptable. I charge both my MacBook Pro 15 and Galaxy S8 with the same Anker charger occasionally. The charger only is rated for 45 W, so the charging of the Macbook Pro is slow. But in a crisis, it works. Your phone charger is likely rated at 15 W, so is going to be very slow to charge your Mac.