Colossal barocaloric effect in GdCl₃-doped H₂O for sustainable cooling

H₂O exists everywhere and its huge latent heat across ice-water phase transition empowers it to be a potential candidate for barocaloric refrigeration applications. Here we report a colossal and reversible barocaloric effect (BCE) in doped H₂O, where the large hysteresis caused by supercooling is solved by adding 1.33 wt% GdCl₃. Thereby the reversible entropy change ΔS_r∼728 J kg^-1 K^-1 has been demonstrated under a low pressure of 0.1 GPa and a more attractive colossal one (1018 J kg^-1 K^-1) can be achieved at 0.16 GPa, exceeding those of all other BCE materials and most of the harmful Freon in vapor compression refrigeration. Neutron measurements combined with molecular dynamics simulations demonstrated that the colossal BCE originates from the breakage/formation of H-bonds in H₂O. Phonon density of states and Raman spectra validate the change of H-bonds from perspective of dynamics. The super BCE performance and the ubiquitous, non-toxic characters make H₂O attractive as barocaloric refrigerant for sustainable cooling, more importantly, it is inferred that H-bond engineering can be an attractive approach for designing novel caloric materials.