You can safely charge a small device like an iPhone on the 145W USB-C 4-Port GaN Travel Charger. A higher-wattage charger does not push extra power into a smaller device.

The charger automatically detects each device and delivers only the wattage that device is designed to accept. An iPhone that needs about 20W to 30W will pull only that amount, even though the charger can supply much more. Using a charger with a higher maximum rating than your device needs will not cause any damage.