# Ag-Cellulose Hybrid Filler for Boosting the Power Output of a Triboelectric Nanogenerator
## 3 Results and Discussion
The electrical outputs of a contact mode TENG are governed by triboelectric charge density (\(\sigma\)), as expressed by open circuit voltage (\(V_{\infty}\)) and short circuit current (\(I_{\infty}\)), which are described by the following equations [47]  
Figure 2.3  
Figure 2.4  
where \(x(t)\) is the working distance, \(v(t)\) is the velocity of the moving electrode, \(S\) is the size of the contact area, \(\varepsilon_{0}\) is the permittivity of free space, and \(d_{0}\) is the effective thickness constant. Triboelectric charge density is dependent on the material types, surface area, and charge capacitance (dielectric constant) of the triboelectric materials [47]. It was observed in this work that the dielectric constant was reduced with increasing Ag concentration. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Specimens** & \(V_{pp}\) **(V)** & \(I_{pp}\) **(\(\mu\)A)** \\ \hline NR & 58 & 5.8 \\ NR-CF & 104 & 9.8 \\ NR-CF@Ag\_1 & 112 & 10.2 \\ NR-CF@Ag\_2 & 120 & 11.8 \\ NR-CF@Ag\_3 & 128 & 12.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Electrical output voltage (\(V_{pp}\)) and current (\(I_{pp}\)) of NR, NR-CF, and NR-CF@Ag\_1–3 TENGs. Figure 7: (**a**) Dielectric constants and (**b**) dielectric loss versus frequency of the NR, NR-CF, and NR-CF@Ag\_1–3 composite films. The surface morphologies of all the NR composite samples were flat, without a change in surface morphology, implying that the size of the surface area was not significantly different among the samples. The enhancement of TENG performance was then deduced from the electrification effect due to the intrinsic property of Ag-cellulose filled NR. This suggested that the main contribution of Ag nanoparticles to the improved electrical output was the promotion of the electron transfer in the electrification event; in other words, the conductive Ag nanoparticles facilitate the electron donating ability of CF in the NR composite. Our results show a similar trend to that noted in the previous study on the cellulose-Ag, where the presence of Ag nanoparticles in cellulose was found to enhance catalytic performance toward the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) [48]. The electrical outputs of the NR-CF@Ag_3 TENG, with the connected load resistances ranging from 0.01-100 \(\mathrm{M}\Omega\), were measured to determine the maximum delivered electrical power of the TENG. The measured output voltage and current at an impact force of 5 N and a frequency of 5 Hz are plotted against load resistances, as presented in Figure 8a. Typically, electrical outputs varied with the load resistance. Output voltage was increased and saturated at high load resistance, whereas output current showed the opposite trend. It is logical that the maximum power transfer is achieved when the internal resistance of the power source is equal to the resistance of load. The calculated power densities (\(P=l^{2}R\)) [49] of the NR-CF@Ag_3 TENG compared to NR-CF and plain NR TENGs are presented in Figure 8b. The maximum power density of 3.65 \(\mathrm{W}/\mathrm{m}^{2}\) was achieved from the NR-CF@Ag_3 TENG at a matched load resistance of 0.7 \(\mathrm{M}\Omega\), which was five times higher than that of the NR TENG (0.68 \(\mathrm{W}/\mathrm{m}^{2}\)) and 1.35 time higher than that of the NR-CF TENG (2.65 \(\mathrm{W}/\mathrm{m}^{2}\)), as given in Table 2. The enhancement of the TENG power output was due to the incorporation of conductive Ag nanoparticles with the combination of electron donating cellulose fibers. The TENG performance was also tested at different impact frequency ranging from 1-10 Hz, as shown by the voltage and current outputs in Figure 8c,d, respectively. The outputs rose and reached up to 312 V and 32 \(\mathrm{\mu}\)A at 10 Hz operation frequency. The increasing electrical output was ascribed to the movement speed of triboelectric layers, which was increased with increasing impact frequency, as described by Equation (2) above.