Pore structure plays critical roles in electrode kinetics but very challenging to tailor porous nanowires with rationally distributed pore sizes in a bioelectrochemical system. Herein a hierarchically porous nanowires-material is delicately tuned for an optimal pore structure by adjusting the weight percentage of SiO₂-hard template in an electrospinning precursor solution. The as-prepared optimal electrospinning nanowires further used as an anode of microbial fuel cells (MFCs), delivering a maximum output power density of 1,407.42 mW·m⁻² with 4.24 and 10 times higher than that of the non-porous fiber and carbon cloth anode, respectively. The great enhancement is attributed to the rational pore structure which offers the largest surface area while the rich-mesopores well match with the size of electron mediators for a high density of catalytic centers. This work provides thoughtful insights to design of hierarchical porous electrode for high-performance MFCs and other bioelectrochemical system devices.

The environment benignity and battery cost are major concerns for grid-scale energy storage applications. The emerging dendrite-free Fe-ion aqueous batteries are promising due to the rich natural abundance, low cost and non-toxicity for Fe resources. However, serious passivation reactions on Fe anodes and poor long-term cyclability for matched cathodes still stand in the way for their practical usage. To settle above constraints, we herein use NH₄Cl as the electrolyte regulator to elevate the reaction kinetics of passivated Fe anodes, and also propose a special cathode-free design to prolong the cells lifetime over 1,000 cycles. The added NH₄Cl can erode/break inert passivation layers and strengthen the ion conductivity of electrolytes, facilitating the reversible Fe plating/ stripping and Fe²⁺ shuttling. The highly puffed nano carbon foams function as current collectors and actives anchoring hosts, enabling expedite Fe²⁺ adsorption/desorption, Fe^II/Fe^III redox conversions and Fe^III deposition. The configured rocking-chair Fe-ion cells have good environmental benignity and decent energy-storage behaviors, including high reactivity/reversibility, outstanding cyclic stability and far enhanced operation longevity. Such economical, long-cyclic and green cathode-free Fe-ion batteries may hold great potential in near-future energy-storage power stations.

It is critical for fabricating flexible biosensors with both high sensitivity and good selectivity to realize real-time monitoring superoxide anion (O₂^•−), a specific reactive oxygen species that plays critical roles in various biological processes. This work delicately designs a Mn₃(PO₄)₂/MXene heterostructured biomimetic enzyme by assembling two-dimensional (2-D) Mn₃(PO₄)₂ nanosheets with biomimetic activity and 2-D MXene nanosheets with high conductivity and abundant functional groups. The 2-D nature of the two components with strong interfacial interaction synergistically enables the heterostructure an excellent flexibility with retained 100% of the response when to reach a bending angle up to 180°, and 96% of the response after 100 bending/relaxing cycles. It is found that the surface charge state of the heterostructure promotes the adsorption of O₂^•−, while the high-energy active site improves electrochemical oxidation of O₂^•−. The Mn₃(PO₄)₂/MXene as a sensing platform towards O₂^•− achieves a high sensitivity of 64.93 μA·μM⁻¹·cm⁻², a wide detection range of 5.75 nM to 25.93 μM, and a low detection limit of 1.63 nM. Finally, the flexible heterostructured sensing platform realizes real-time monitoring of O₂^•− in live cell assays, offering a promising flexible biosensor towards exploring various biological processes.