# Ag-Cellulose Hybrid Filler for Boosting the Power Output of a Triboelectric Nanogenerator
## 3 Results and Discussion
The short contact cycle at high movement speed caused the retention of triboelectric charges, giving rise to the enhancement of electrical output [14; 37]. At low working frequency, the reasonable electrical outputs were obtained. This suggested that the fabricated TENG could be used to harvest mechanical energy, with various frequency ranges. Figure 8: _Cont._  
The influence of the impact force on TENG performance was also investigated. The electrical outputs of the TENG tested at various impact forces from 2-10 N are displayed in Figure 9a. It was shown that the TENG outputs increased with the greater impact force. When the triboelectric layers were pressed by the applied force, their thicknesses were reduced, leading to the increased charge capacitance [14], as described by C = \(\varepsilon_{0}\varepsilon_{r}A/d\), where \(A\) is the contact area and \(d\) is the thickness of the triboelectric layer. The greater the impact force, the larger the film deformation, resulting in the higher electrical output of the TENG. The performance stability of the TENG was also tested with the constant applied force of 5 N at 5 Hz impact frequency for 10,000 cycles. It was found that the NR-CF@Ag TENG exhibited good performance stability with 82% output retention, as presented in Figure 9b. The reduction in performance stability could be due to the mechanical degradation of the NR composites. This could be explained by the fact that the NR composite was fabricated from a prevulcanized latex, meaning that it already contained a cross-linking agent. Adding CF did not change the chemical structure of the NR composites, as evidenced by the FTIR results (Figure 5b). This suggested that CF did not improve the mechanical strength of the composites, and it could disrupt the cross-linking reaction in NR due to the large fiber size [50]. Our fabricated TENG showed performance stability superior to that of the TENG made from the nanofiber/microsphere hybrid membranes (77% retention) [51] and comparable to that of our previously reported cellulose paper-based TENG (85% retention) [37] over the same number of impact cycles. The application of the fabricated TENG as a power source was also demonstrated to charge commercial capacitors by the use of a bridge rectifier. Figure 9c shows the voltage profiles of the 10, 22, 37, and 100 uF capacitors, which were charged by the NR-CF@Ag_3 TENG under the impact force of 5 N and at 5 Hz frequency. The TENG was able to charge a device as small as a 10 uF to 3.5 V in 400 s and as large as a 100 uF capacitor to 1.5 V in 500 s (~8 min). The generated electrical power from TENG was also able to instantaneously operate 100 commercial green LEDs, as \begin{table}
\begin{tabular}{c c} \hline
**TENGs** & **Power Density (W/m2)** \\ \hline NR–CF@Ag\_3 & 3.65 \\ NR–CF & 2.65 \\ NR & 0.68 \\ \hline \end{tabular}
\end{table} 
Table 2: Power density of the NR–CF@Ag_3 TENG compared to the NR and NR–CF TENGs. Figure 8: (**a**) Output voltage and current measured with the connected load resistances and (**b**) the corresponding power density of the NR–CF@Ag_3 TENG. The impact frequency dependence of (**c**) the TENG output voltage and (**d**) current outputs. displayed in Figure 9d. These results suggested the potential application of the NR-CF@Ag TENG as a power source for microelectronic devices.