. 2019 Sep 26;9:13945. doi: 10.1038/s41598-019-50118-y

Table 1.

Properties of potential redox refrigerants.

Redox reaction	α, mV/K	YT = ΔТ_max @300K, K	Q_g/b @300K
2 H⁺ + 2e⁻ → H₂ (g)	0.8	307	4.0^9,27
V³⁺ + e⁻ → V²⁺	1.2–1.9*	36	6.0²⁸
V⁵⁺ + e⁻ → V⁴⁺	−0.2*	6	2.4²⁸
Br₂(l) + e⁻→ 2Br⁻	0.3*	14	1.7²⁹
Fe(CN)₆³⁻ + e⁻ → Fe(CN)₆⁴⁻	−1.5*	10.6	78.4³⁰
Fe³⁺ + e⁻ → Fe²⁺	1.1*	36	95.7³¹
Cr³⁺ + e⁻ → Cr²⁺	2.2	7	219.5^9,23,31
Ce⁵⁺+e⁻ → Ce⁴⁺	2.3	13	36.0^9,32
S₂²⁻ + 2e⁻ → 2S²⁻	−0.7	9.4	1.3^9,33

Q_g/b and YT = ΔТ_max are listed to illustrate the trade-off between overall cooling capacity, reversibility, and thermopower. Properties of reduction reactions denoted ‘*’ were measured expressly for this work, as described in the SI. Entropy of reduction varies with total concentration for some species. In these cases, ΔТ_max and Q_g/b were calculated based on the concentration yielding the highest ΔТ_max. Activation energies E_a were estimated based on literature sources for exchange current density or reaction velocity, as described in the SI.