In Situ Formation of Fe–N–C Coordinated on Graphite Felt as a Self-Supporting Electrode for Thermoelectrochemical Cells

With the growing global demand for sustainable energy solutions, there is increasing interest in the conversion of low-grade heat into useful electrical energy. Thermoelectrochemical cells (TECs) are a promising technology for low-grade heat harvesting. However, sluggish reaction kinetics limit the power generation and efficiency of the TECs. In this study, we propose a Fe–N–C catalyst in situ grown on three-dimensional graphite felt as a self-supporting electrode for TECs. The graphite felt substrate provides a multidimensional structure to facilitate mass transport, while the Fe–N–C catalyst enhances electrode activity for redox reactions. The physicochemical properties and electrochemical performance of the electrode are characterized. The results demonstrate that the optimized electrode achieves a maximum power density of 1938 mW/m2 and a Carnot-relative efficiency of 2.29%, representing 11-fold and 12-fold improvements over graphite felt, respectively. These metrics surpass recent benchmarks in the field of TEC research. Furthermore, the electrode maintains a Carnot-relative efficiency of 2.0% in solar-driven TEC operation, demonstrating feasibility in photothermal and thermoelectrochemical conversion. Modeling analysis reveals that ion transport dominates heat and mass transfer processes, critically influencing power generation and stability, thereby highlighting the need for future optimization of ion transport pathways. This work validates the feasibility of in situ-grown Fe–N–C catalysts on graphite felt as high-performance TEC electrodes, offering a strategic framework for advancing waste heat recovery systems through rational electrode design and transport engineering.