*2.2. Preparation of TOCNFs, TOCNF-CNT Nanohybrids, and TOCNF-CNT@PANI Nanohybrids*

The bleached wood pulp solution was mixed with TEMPO and NaBr by means of mechanical stirring. Then, NaClO (15 mmol g−<sup>1</sup> cellulose) solution was added to initiate an oxidation reaction. The value of pH should be maintained at 10.5 by adding 1 M NaOH solution in the reaction process. After the oxidation reaction, the achieved fibers were washed by DI water and ultrasonicated at 800 W power for 3 min to obtain TOCNFs [10]. The concentration of final homogenized suspension was adjusted to 0.6 wt%.

A total of 0.5 g CNT powers was added to the 62.5 g 0.6 wt% TOCNFs suspensions at the mass ratios m(CNTs):m(TOCNFs) = 1:0.75 while keeping mechanical agitation for 30 min. Then, they were diluted to 500 mL water and ultrasonicated for 10 min at 400 W power in an ice bath to achieve TOCNF-CNT nanohybrids homogenized aqueous dispersion. The sonication was carried out by a high-energy ultrasonic cell disruptor.

TOCNF-CNT@PANI nanohybrids were synthesized based on TOCNF-CNT nanohybrids as a template and APS as oxidant through in-situ polymerization in an acidic water medium, as follows. First, 50 mL 1 M HCl solution containing 0.875 g ANI (0.0094 mol) was added into the 500 mL TOCNF-CNT nanohybrids dispersions and stirred for 10 min in an ice bath. Next, 50 mL 1 M HCl solution containing 2.68 g APS (0.01175 mol, mole ratio of ANI:APS = 1:1.25) was added slowly to the mixture in 30 min. During the process, the uniform mixture was slowly converted to blue tone, indicating polymerization; then, the solution was kept stirring for 6 h and stand for 12 h in an ice bath to complete polymerization. Finally, the obtained TOCNF-CNT@PANI nanohybrids were washed by vacuum filtration, and the excess unreacted ions were removed. The washed product was transferred to dialysis tubes and dialyzed to pH = 7.

A similar method was used to synthesize TOCNF-CNT@PANI nanohybrids containing different PANI content. The mass ratio of ANI monomers to TOCNF-CNT nanohybrids were 0:1, 1:1, 2:1, and 3:1, and the corresponding TOCNF-CNT@PANI nanohybrids samples were denoted TOCNF-CNT, TOCNF-CNT@PANI-1, TOCNF-CNT@PANI-2, and TOCNF-CNT@PANI-3, respectively.
