Radiation heat dissipation substrate, radiative cooling device containing the same and preparation method thereof

A radiative cooling substrate, comprising:

• a metal substrate having a first surface and a second surface in opposite, wherein the metal substrate is a stainless-steel substrate without other layers;
• a broadband radiation absorption layer located on the first surface of the metal substrate, wherein the broadband radiation absorption layer is a chitosan carbon black layer without other layers, and the chitosan carbon black layer is electrophoresis deposited from a chitosan carbon black solution prepared by adding 0.1-0.3 g of carbon black powder to every 250 mL of chitosan solution;
• and
• a wavelength-selective infrared emission layer located on the second surface of the metal substrate, wherein the wavelength-selective infrared emission layer is a chitosan layer without other layers.