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Anaerobic digestion pretreatment was conducted to assist electrocatalyst preparation.The biological pretreatment succeeded in carbohydrates decomposition and nitrogen enrichment.Pretreatment derived biochar significantly increased the ORR activity and microbial fuel cell performance.

Developing high-rate anode materials for sodium-ion batteries is important to fulfill the requirement of high-power energy storage applications. Amorphous carbon micro-tubes (CMTs) are favorable for fast Na-ion storage, for the open carbon framework provides sufficient electrode/electrolyte contact and the one-dimensional skeleton offers fast electron and ion diffusion pathways. Herein, N, Fe co-doped carbon micron-tubes (NF-CMTs) were synthesized for the high-rate anode by using bulk biomass as the precursor. The transformation from the macro-sized biomass to the micro-sized carbon tubes was endowed by pyrolysis using N and Fe as catalysts. The open carbon frameworks enable capacitive-controlled capacity contribution, while its N-Fe defects offer multiple active sites for fast Na-ion storage. A high-capacity contribution was demonstrated by the pseudo-capacitive mechanism so that the NF-CMTs performed a superior rate capability of 120 mAh g−1at 2.0Ag−1. The NF-CMTs with stable micro-tube frameworks exhibited high cycling stability over 1200 cycles, which was much superior to the commercial hard carbon anode. This study provides a cost-effective approach to develop carbon micro-tubes from bulk biomass for high-power SIB anodes.