## 2 Reaction Mechanisms and Kinetics of Electrocatalytic Nitrate Reduction
### Advances in Electrocatalyst Preparation Techniques for Efficient Nitrate Reduction  
#### 3.1.1 Electrodeposition  
Electrodeposition involves depositing material onto an electrode by applying an electrical current or potential in an electrochemical cell. The performance of electrodeposited electrocatalysts is highly dependent on the specific electrodeposition parameters used. To optimize these electrocatalysts, a detailed investigation is needed to understand how different parameters affect the deposition process [81]. Key factors, such as the choice of electrolyte, electrodeposition time, mode of electrodeposition, and the presence of additives, play a crucial role in shaping the performance of the deposited electrocatalyst. Regarding that, [PERSON] et al. [82] investigated how the electrolyte in the electrodeposition process affects the morphology of copper nanoparticles, specifically on Vitreous Carbon (VC) substrate, observing that Na\({}_{2}\)SO\({}_{4}\) solution led to flower-shaped dendritic structures; however, H\({}_{2}\)SO\({}_{4}\) produced randomly distributed hemispherical particles. The differences in morphology on VC were linked to substrate defects interacting with the electrolytic media, affecting the nucleation and growth of the crystals [82]. Another factor which is the electrodeposition time, plays a crucial role in the performance and electrocatalysts stability for nitrate reduction. Specifically, longer deposition times can lead to issues with electrode stability, as seen in the case of Cu-BDD electrodes. For instance, a copper oxide layer formed after 600 s of electrodeposition was prone to detachment during electrochemical nitrate reduction. This instability can hinder the electrocatalyst's performance and longevity. In contrast, a deposition time of 300 s was found to be optimal. At this duration, copper particles formed on the Cu-BDD surface were unevenly distributed with diameters ranging from 72.7 to 139 nm, and an average size of 106 nm. The shorter deposition time resulted in better particle adhesion and electrode stability, making it more suitable for eNOS\({}_{3}\)R [83]. Another study by [PERSON] et al. [84] demonstrated that longer electrodeposition times result in higher Cu loading on the electrode, enhancing NO\({}_{3}^{-}\) removal due to increased catalytic activity. However, after 15 min, Cu is evenly distributed on the Ni foam surface, and additional electrodeposition time does not significantly increase active sites. Additionally, extended electrodeposition times (25 and 35 min) can lead to Cu agglomeration, which reduces the degradation rate of NO\({}_{3}^{-}\)[84]. The advantage of the electrochemical deposition method is its ability to synthesize electrocatalysts with specific crystallographic facets tailored to needs. For example, [PERSON] et al. [85] synthesized Tetrahexahedral Cu nanocrystals (THH Cu NCs) with \(\{5\;2\;0\}\) facets using a programmed square-wave potential (SWP) method, which allows precise control over the exposed crystallographic facets by adjusting potential limits. The synthesized THH Cu[5 2 0] nanocrystals demonstrated exceptional catalytic activity and selectivity in the electrochemical reduction in nitrate, achieving a Faradaic efficiency of 98.3% at \(-\)0.90 V (vs. RHE) in neutral solution [85]. However, the drawback of this electrocatalyst preparation method is the instability of the electrodes. According to [PERSON] et al. [86] who developed Pd/Cu electrocatalysts with electrodeposition durations between 60 and 360 s, Pd/Cu 180 s demonstrated superior nitrate removal efficiency and nitrogen selectivity. However, ICP analysis identified a Pd concentration of 0.063 ppm after prolonged reaction times, highlighting the necessity for future improvements in electrode stability, possibly by adding other treatments [86].