Highly efficient utilization of crop straw-derived biochars in direct carbon solid oxide fuel cells for electricity generation

Efficient and stable operation of direct carbon solid oxide fuel cells (DC-SOFCs) hinges upon the kinetics of the reverse Boudouard reaction. Crop straw, possessing exceptional physicochemical properties, exhibits great potential to promote the reverse Boudouard reaction and cell performance. Here, we successfully developed two representative biochars derived from sesame and eggplant straw, conducting thorough physicochemical characterization and evaluating their application in DC-SOFCs. Results revealed a substantial impact of biochar intrinsic properties on DC-SOFC performance. At 850 degrees C, the single cell employing sesame straw biochar achieved the highest output of 228 mW cm(-2), while the DC-SOFC fueled with eggplant straw biochar yielded 214 mW cm(-2), both surpassing the 173 mW cm(-2) output of the activated carbon-powered cell. Furthermore, the sesame straw biochar-fueled cell exhibited the longest operational lifetime of 30.7 h, with a fuel utilization as high as 34.4% at 850 degrees C and 50 mA. Similarly, the operational lifetime and fuel utilization of the eggplant straw biochar-fueled DC-SOFC were recorded as 21.1 h and 23.6%, respectively. These outcomes consistently outperformed activated carbon-powered DC-SOFC, demonstrating the crucial role of crop straw-derived biochar in enhancing DC-SOFC stability and efficiency. The improved cell performance was ascribed to the biochar's porous structure, larger specific surface area, more disordered carbon, and naturally occurring metal catalysts, which effectively accelerated the reverse Boudouard reaction and ensured an abundant provision of carbon monoxide for DC-SOFC operation.