Improving Seebeck coefficient of thermoelectrochemical cells by controlling ligand complexation at metal redox centers

Abstract

Practical conversion of waste heat into electricity via thermoelectrochemical cells requires high Seebeck coefficient (α) to increase cycle efficiency. The complexation of Cu2+ species with dissolved multidentate ligands, such as ethylenediaminetetraacetic acid, and the control of dimerization equilibria with bridging ligands, such as 1,6-diaminohexane or 1,2-diaminoethane, dramatically improve, by up to ∼185%, the magnitude of the α of Cu/Cu2+ thermoelectrochemical cells. This results in the highest α for any Cu/Cu2+ redox system yet reported. The coefficient α is directly proportional to the change in entropy (ΔS). It was experimentally measured and correlated with ΔS obtained from quantum-chemical methods. This offers a deeper insight about a molecule-based interpretation of the macroscopic response. The agreement between the theoretically estimated and experimentally observed α is remarkable. Hence, we believe that this synergistic approach allows us to systematically scan different systems to obtain efficient thermoelectrochemical cells with enhanced Seebeck coefficient.

Thermoelectrochemical Seebeck coefficient and viscosity of Co-complex electrolytes rationalized by the Einstein relation, Jones–Dole B coefficient, and quantum-chemical calculations

“…So far, the use of the quantum-chemical method to explain the Se of TEC is still limited. Recently, Gunawan et al 49 applied this method to the Cu/Cu 2+ system with flexible ligands and showed that the Se values calculated under assumed ligand conformations were on the same order as the measured values.…”

Optimal fabrication of a thin-film thermocouple (TFTC) using Alumel/chromel junctions

“…There are various methods for improving the Seebeck coefficient of materials. Techniques such as hydrazine treatment [ 22 ], ionic liquid post-processing [ 23 ], alloying [ 24 ], control of material alignment [ 25 ], and energy filtering through nanoparticle deposition [ 26 ] can be employed to enhance the Seebeck coefficient. However, in this work, we focused on creating sensors using commonly available materials from the market without additional processing steps.…”

High-Power-Density Thermoelectrochemical Cell Based on Ni/NiO Nanostructured Microsphere Electrodes with Alkaline Electrolyte

“…The energy generation mechanism can be based on both phase and chemical transformations of electrolytes [ 17 ] and redox processes in the electrolyte, while the electrodes are inert [ 18 , 19 , 20 ]. Another type of thermocells are systems with reversible electrodes [ 2 , 21 , 22 ]. These systems require a regular change of the thermal gradient direction; however, they show a rather high efficiency level and a hypothetical Seebeck coefficient for systems with aqueous electrolytes [ 16 ].…”