Innovative application of tomato straw biochar in direct carbon solid oxide fuel cells for power generation

Direct carbon solid oxide fuel cells (DC-SOFCs) demonstrate significant promise in clean energy conversion technology due to their direct utilization of solid carbon, high-temperature operation, and fuel flexibility. Exploring biomass as a fuel for DC-SOFCs is particularly intriguing within this context. Here, we successfully developed the biochar derived from tomato straw and conducted a comprehensive physicochemical characterization to investigate its feasibility and advantages for DC-SOFCs. Electrochemical results revealed that DC-SOFC powered by tomato straw biochar achieved an impressive output of 219 mW cm⁻² at 850 °C, surpassing the cell output of 187 mW cm⁻² operating on commercial activated carbon. Furthermore, the single cell demonstrated a higher discharge plateau and a longer lifetime of 26.5 h under 50 mA at 850 °C. Consequently, fuel utilization was calculated to be up to 29.7%, which was also superior to that of activated carbon-fueled DC-SOFC, further validating the effectiveness of tomato straw biochar in improving DC-SOFC performance. These outstanding performances were primarily attributed to the unique porous microstructure, naturally existing metal elements, high disorder and large specific surface area of the biochar, which effectively promoted the reverse Boudouard reaction to produce a substantial amount of CO for anode reaction, thus enhancing the DC-SOFC performance and efficiency. These findings underscore the enormous application potential of tomato straw biochar for DC-SOFCs, providing strong support for advancing clean energy technology and achieving carbon neutrality goals.