Lattice regulation of molybdenum dioxide via Fe doping for high-performance electrodes of thermo-electrochemical cells

One of the key challenges in the development and application of thermo-electrochemical cells (TECs) as energy-harvesting systems is the availability of economically feasible electrode materials. In this study, a Fe-doped molybdenum dioxide (MoO 2 ) with Pt-like electrochemical performance was feasibly synthesized via a solvothermal method combined with an annealing treatment. The obtained Fe-doped MoO 2 (Fe–MoO 2 ) displays a uniform spherical morphology with an average size of 24 nm. Moreover, Fe doping reduces the lattice spacing and modulates the electronic structure of MoO 2 . Thereby, the optimized Fe–MoO 2 exhibits a high active surface area (ESA = 1.69 cm 2 ) and very low contact potential difference (CPD = 0.097 V), showing a short-circuit current density ( J sc  = 0.520 mA cm −2 ) and a maximum power density ( P max  = 5.07 μW cm −2 ) better than pure MoO 2 (0.464 mA cm −2 , 4.72 μW cm −2 ) and comparable to commercial Pt (0.517 mA cm −2 , 4.97 μW cm −2 ) electrodes in TECs (ΔT = 25.2 K). Additionally, this Fe–MoO 2 -based TEC maintains stable voltage and current over 7 h, indicating excellent stability and reversibility in the cycling tests. This study demonstrates that Fe-doped MoO 2 can serve as a low-cost, high-performance electrode material for TECs, offering a new solution for low-grade heat recovery.