## 3 Results and Discussion
### Effect of Discharge Parameters on \(\mathrm{NH}_{3}\) Formation  
The impact of pulse voltage on the discharge is notably crucial, given that pulse voltage is instrumental in the ionization process of N\({}_{2}\) and H\({}_{2}\). Figure 5a,b show the effect of different pulse voltages on the effect of ammonia synthesis. As shown in Figure 5a, without addition of noble gases, the ammonia synthesis rate rises and then decreases with increasing voltage, indicating that when the voltage exceeds 13 kV, more input energy can promote the ammonia decomposition reaction. After the addition of noble gas, the ammonia synthesis rate did not decrease with increasing voltage. The increase of voltage makes the ionization of gas molecules more intense, which makes the rate of electron collision reaction greatly increase, so the increase in voltage can effectively promote ammonia synthesis. Figure 5b shows that after introducing Ar and He, the ammonia synthesis rate rises with an increase in voltage, yet the peak energy yield for both is attained at 13 kV. This means that after the discharge voltage exceeds 13 kV, the energy utilization of ammonia synthesis decreases with increasing voltage for the same input energy. Since the increase in voltage also increases the probability that Ar and He will collide with electrons, this consumes some of the input energy. As for the increase in the rate of ammonia synthesis, we attribute it to the increase in the number of active particles of Ar and He, whose collisions with other particles produce more reactive substances such as N\({}_{2}\)+, N\({}_{2}\)+, and H\({}_{2}\)*. The mechanism of generation of active species will be described in detail later. This is because more non-surface reaction pathways compared to the case without the addition of noble gases means that intermediate reactants can be produced by more particle collisions, especially reactive particles of N\({}_{2}\), which have the rate-limiting effect on the reaction [43]. Figure 5c,d illustrate how variations in pulse frequency impact the rate of ammonia synthesis and the efficiency of energy yield. Increasing the pulse repetition frequency increases the electron density and the amount of active material due to the increased energy input within the discharge period. Figure 5c reveals that the rate of ammonia synthesis progressively rises with an increase in pulse repetition frequency. The reason is that a higher pulse frequency augments the charge within the discharge channel, thereby enhancing discharge activity. This amplification in discharge intensity boosts collision  
Figure 4: Effect of the addition of (**a**) Ar and (**b**) He on the energy yield of the synthesis of ammonia. chances, leading to a surge in high-energy electron generation per unit time, which in turn elevates the ammonia synthesis rate. Figure 5d shows that the energy yields for both the cases without and with the addition of noble gases have a maximum at a pulse repetition frequency of 1200 Hz. The pulse repetition frequency begins to decrease when it exceeds 1200 Hz, and too high a pulse repetition frequency leads to a decrease in energy yield. The power formula indicates that a rise in frequency corresponds to an increase in discharge power. However, the energy yield from ammonia synthesis diminishes when the pulse repetition frequency becomes excessively high. However, for ammonia synthesis, which is a reversible reaction, we cannot intuitively determine from the conclusions whether an increase in frequency results in facilitated ammonia decomposition. The effect of pulse width on the rate and energy yield in the three systems is shown in Figure 6a,b. It can be seen that increasing the pulse width decreases the energy yield. Increasing the pulse width decreased both the synthesis rate and the energy yield without the addition of noble gases. In contrast, the addition of Ar and He gave the best results at a pulse width of 120 ns.