# The Effects of Acidic, Alkaline, and Neutral Anolytes on Electrochemical Seawater Deoxygenation
## 3 Results and Discussion
### Buffer Solutions  
Buffer solutions with pH 2.6, 7.0, and 9.1 at different applied potentials (from 1.9 to 2.3 V) were examined in Cell B. The cathode potential was found to decrease with an increase in the cell voltage as shown in Figure 4. The cathode potential in acidic solution at 2.3 V (\(-\)80 mV vs. RHE) indicated that there was no production of hydrogen in the acidic solution on the silver surface. The H\({}_{2}\)O\({}_{2}\) concentration was measured to be 0.3 ppm and 0.1 ppm at 1.9 V and 2.0 V applied voltages in acidic solution, respectively, giving cathode potentials of 253.2 mV and 160 mV (vs. RHE), respectively. H\({}_{2}\)O\({}_{2}\) production was not evident in the alkaline and neutral buffer solutions, and the cathode potentials were also observed to be more negative compared to cathode potentials in the acidic buffer solution.  
The current outputs in relation to cell voltage in acidic, basic, and neutral buffer solutions are shown in Figure 5. As expected, an increase in cell voltage increased the current output. The alkaline buffer anolyte showed the highest current output, followed by neutral and acidic anolytes. The conductivity of the solutions were considered responsible for such variation of current output, as the basic buffer had the highest conductivity (20 mS-cm\({}^{-1}\)), while the acidic buffer had the lowest (1.30 mS-cm\({}^{-1}\)).  
The cathode potentials for the acidic, alkaline, and neutral solutions were also in the acceptable range at a cell voltage of 2.2 V. A too negative potential would cause hydrogen gas evolution. In the  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Time** & **Voltage** & **Current** & **Oxygen Conc.** & **Analytic Conductivity** & **Anolyte pH** & **Catholyte Conductivity** & **Catholyte pH** \\ (min) & **(V)** & **(mA)** & **(ppm)** & **(mS-cm\({}^{-1}\))** & **Anolyte pH** & **(mS-cm\({}^{-1}\))** & **Catholyte pH** \\ \hline
**0** & **-** & **-** & 8.10 & 10.0 & 6 & 46.5 & 6 \\
**30** & 1.9 & 10 & 2.72 & 10.0 & 4 & 46.5 & 8 \\
**60** & 2.0 & 11 & 2.52 & 10.0 & 4 & 46.5 & 8 \\
**90** & 2.1 & 10 & 2.00 & 10.2 & 4 & 46.6 & 8 \\
**120** & 2.2 & 11 & 1.81 & 10.2 & 4 & 46.6 & 9 \\
**150** & 2.3 & 12 & 1.86 & 10.2 & 4 & 46.7 & 9 \\ \hline \end{tabular}
\end{table}
Table 4: Effect of voltage on oxygen removal, pH, and conductivity in 0.1 M NaNO\({}_{3}\) anolyte.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Time** & **Voltage** & **Current** & **Oxygen Conc.** & **Analytic Conductivity** & **Anolyte pH** & **Catholyte Conductivity** & **Catholyte pH** \\ (min) & **(V)** & **(mA)** & **(ppm)** & **(mS-cm\({}^{-1}\))** & **Anolyte pH** & **(mS-cm\({}^{-1}\))** & **Catholyte pH** \\ \hline
**0** & **-** & **-** & 8.18 & 42.8 & 1 & 47.1 & 5 \\
**30** & 1.9 & 10 & 2.99 & 43.2 & 1 & 46.8 & 5 \\
**60** & 2.0 & 12 & 2.25 & 43.1 & 1 & 46.8 & 5 \\
**90** & 2.1 & 15 & 2.20 & 43.1 & 1 & 46.8 & 5 \\
**120** & 2.2 & 21 & 2.13 & 43.1 & 1 & 46.7 & 5 \\
**150** & 2.3 & 27 & 1.60 & 43.0 & 1 & 46.  
buffer solution, the potential ranges for the cathode for all solutions were in the range of 250 mV to \(-\)260 mV. The formation of hydrogen gas was not observed in the cell, and based on the overpotential for hydrogen production on silver, no significant side reactions were expected.