Flexible, compressible, versatile biomass-derived freestanding carbon monoliths as binder- and substrate-free tri-functional electrodes for solid-state zinc-air batteries and overall water splitting

Highly flexible and compressible biomass-derived freestanding monoliths are directly utilized as binder- and substrate-free tri-functional electrodes for the wearable electronic devices. The introduction of Co nanoparticles, nanoclusters, and single atoms onto biomass-derived monoliths leads to the additional growth of CNTs for ensuring the interconnectivity of 3D cellulose-derived carbon network. Thus, superb flexibility and/or compressibility as well as high-efficiency tri-functional activity are achieved simultaneously. The alkaline water electrolyzer with monolithic electrodes requires only a potential of 1.56 V to generate hydrogen at a current density of 50 mA cm−2 for over 120 h. Furthermore, the quasi-solid-state zinc-air batteries(ZABs) exhibit a high peak power density of 175.5 mW cm−2, and an optimal charge-discharge overpotential with a remarkably small voltage gap (∆V) of 0.27 V at 5 mA cm−2. The excellent charge-discharge cycle stability even under bending and compression conditions demonstrates its high potential for emerging next-generation electronics devices. [Display omitted] •The waste biomass was converted into a variety of freestanding carbon monoliths.•CNTs-decorated carbon networks contain cobalt nanoclusters and single atoms.•Freestanding monoliths exhibits an excellent tri-functional activity.•Monoliths were applied directly to alkaline water electrolyzers and ZABs.•Interconnected fibrous networks lead to excellent flexibility and compressibility.