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A direct carbon solid oxide fuel cell is a new technology for clean and efficient utilization of carbon resources to generate electricity, with the advantages of high power generation efficiency and wide available fuel flexibility. Biomass, in virtue of large specific surface area, numerous oxygen-containing functional groups which can promote the electrooxidation of carbon, and low ash content which can increase the cell stability, reveals promising feasibility as a fuel for direct carbon fuel cells. Here we report a high-performance direct carbon fuel cell utilizing Chinese parasol leaf biochar as fuel, among which Ag–Gd0.1Ce0.9O2-δ and Al2O3 doped yttria-stabilized zirconia are employed as symmetrical electrodes and electrolyte materials, respectively. The cell with pure leaf biochar fuel gives a maximum power density of 249 mW cm−2 and an open circuit voltage (OCV) of 1.008 V at 850 °C while an improved performance of 272 mW cm−2 and OCV of 1.01 V are achieved for the cell fuelled by Fe catalyst-loaded leaf biochar. The above results demonstrate that Chinese parasol leaf biochar can be applied as a potential fuel for high performance direct carbon solid oxide fuel cells.

Direct carbon solid oxide fuel cell (DC-SOFC) is a larruping type of fuel cell due to its all-solid-state structure, which can generate electricity from converting the chemical energy contained in solid carbon fuels directly into electrical energy. As the most abundant carbon storage base on earth, besides commercial carbon, coal or the common biomass carbon fuels, the exploitation of marine biomass as an alternative fuel for DC-SOFC is a very intriguing topic. In order to make efficient utilization of biomass carbon obtained from the ocean, a high performing direct carbon solid oxide fuel cell fuelled by kelp biochar is demonstrated. As comparison, the performances of DC-SOFCs with activated carbon and catalyst-loaded activated carbon fuels are also investigated. Thereinto, the best performance of 285 mW cm−2 at 850 °C is achieved in a DC-SOFC using kelp biochar fuel with Ag-Gd0.1Ce0.9O2-δ /YSZ/ Ag-Gd0.1Ce0.9O2-δ configuration. This study will provide promising utilization of alternative biomass in DC-SOFCs and broaden their available carbon scope.