Polypyrrole (PPy)@cellulose fiber-based composites have been widely investigated as electrode materials for use in flexible supercapacitors. However, they cannot readily provide high specific capacitance and cyclic stability owing to their inherent drawbacks, such as high resistance, Weber impedance, and volume expansion or collapse during charging/discharging. In this study, iron oxyhydroxide (FeOOH) is incorporated in the abovementioned composite to decrease the equivalent series resistance, charge transfer resistance, and Weber impedance, thereby enhancing electron transfer and ion diffusion, which results in superior electrochemical performance. The PPy-wrapped FeOOH@cellulose fiber-based composite electrode with the molar ratio of FeSO₄ to NaBH₄ of 1∶1 exhibits a high specific capacitance of 513.8 F/g at a current density of 0.2 A/g, as well as an excellent capacitance retention of 89.4% after 1000 cycles.

The removal of formaldehyde (HCHO) from indoor air is of great importance to reduce health risks and improve indoor air quality. In this study, nano-Cu₂O-loaded paper with superior photocatalytic activity under visible light for the removal of HCHO was fabricated through a green, simple, and fast in situ synthesis method. The optimum preparation conditions for nano-Cu₂O-loaded paper were as follows: 2 g (oven-dry basis) cellulose fibers, CuSO₄ dosage 8 g, NaOH dosage 1.6 g, temperature 2+ 80℃, 60 min for Cu²⁺ absorption, and 60 min for reaction. Under the optimum conditions, the Cu₂O deposition ratio approached 30% and the nano-Cu₂O-loaded paper exhibited a catalytic efficiency of approximately 97% for HCHO removal. The photocatalytic capacity of nano-Cu₂O-loaded paper for HCHO removal had a positive correlation with the deposition ratio of nano Cu₂O particles. Excellent antibacterial property of nanoCu₂O-loaded paper against Staphylococcus aureus and Escherichia coli was also confirmed. Moreover, nano-Cu₂O-loaded paper was proven to be hydrophobic.