# Ag-Cellulose Hybrid Filler for Boosting the Power Output of a Triboelectric Nanogenerator
## 3 Results and Discussion
In this work, the NR-CF@Ag TENGs were fabricated and their performances were evaluated under a single electrode mode. The TENG device configuration and working mechanism are illustrated in Figure 6. The NR-CF@Ag films consisted of positive tribomaterial coated on an ITO conductive electrode, which were tested with a PTFE negative tribomaterial. The electricity is generated under the repeated contact-release cycle of PTFE (top) and the NR-CF@Ag (bottom) surfaces. At state i, the electrification effect occurs when two surfaces are in contact, and electrons are transferred from the NR-CF@Ag films to PTFE due to the high electron affinity of PTFE, giving rise to the formation of positive and negative surface charges on the NR-CF@Ag films and PTFE, respectively. When the surfaces are released in states ii-iii, the electrical potential is created, and the electrostatic induction works by inducing free electrons to flow from the ground to the ITO conductive glass to neutralize  
Figure 5: (**a**) XRD spectra and (**b**) FTIR transmittance spectra of NR, NR–CF, and NR–CF@Ag_1–3 composite films. the potential. At this state, a positive current signal is created. Once the surfaces are back in contact (state iv), the potential is reduced, and free electrons flow back to the ground, generating an electric current in the opposite direction (negative current). The plots of the output voltage and current signals of all the fabricated TENGs are presented in Figure 6b,c, respectively, and the peak-to-peak output values are given in Figure 2.0 It was observed that the electrical outputs of the TENG were significantly improved after adding CF, which was consistent with our previous study using cellulose nanofibers [21]. The improvement in the electrical output was attributed to the electron donating properties of cellulose due to the presence of oxygen in their hydroxyl functional groups [44; 45]. The incorporation of Ag nanoparticles further improved the TENG performance, which increased with increasing Ag content. The highest electrical output voltage and current (peak-to peak) of 128 V and 12.4 uA were obtained from the NR-CF@Ag_1-3 TENGs, which were higher than those of pristine NR TENG (58 V and 5.8 uA) and NR-CF TENG (104 V and 9.8 uA). The electrical outputs showed an increasing trend with Ag nanoparticle concentration. However, preparing Ag nanoparticles at high concentrations led to the precipitation of Ag with a large particle size, which was not suitable for use. Figure 2.1 (**a**) The TENG working mechanism in a single electrode mode; (**b**) output voltage and (**c**) current of the NR, NR–CF, and NR–CF@Ag_1–3 TENGs under 5 N impact force at a working frequency of 5 Hz. The role of Ag nanoparticle in the improvement of TENG performance was examined by measuring the dielectric properties of the NR-CF@Ag composite films to probe the charge retention properties of the films, which are presented in Figure 2.2 It was noted that the dielectric constant of the NR-CF@Ag was reduced with increasing Ag concentration (Figure 7a), which was lower than those of NR and NR-CF, respectively, whereas the dielectric loss did not show a correlation with the electrical outputs (Figure 7b). The result from this work showed a different trend from that in our previous study on NR-Ag TENG [14], where the dielectric constant increased with increasing Ag nanoparticle concentration, and which was affected by the nanoparticle's capping agents. In the present work, no capping agent was used for synthesizing Ag nanoparticles; therefore, the dielectric polarization was disrupted. The addition of Ag nanoparticles without the capping agent results in the connection of the particles, forming the electrical conductive path and giving rise to the reduction of the dielectric constant [46].