## 3 Results  
### Biomembrane Characterization in a Coupled Electrolyzer Cell  
In order to evaluate the effect of each treatment, the bio-membrane was incorporated into the electrolyzer cell using NaOH (0.1 M) as the electrolyte solution in the two chambers. All experiments were performed at room temperature (298 K), an applied current of 4.4 mA was used while the potential (V) of the electrolyzer cell was being recorded. Electrical resistance (R, \(\Omega\)) was measured, and ion mobility (\(\sigma\), mS cm\({}^{-1}\)) was then estimated according to Equation (1), where \"\(l\)\" is the membrane thickness (cm), and \"A\" is the cross-sectional area (A, 4.0 cm\({}^{2}\)) [34].  
\[\sigma=\frac{l}{R*A} \tag{1}\]  
A continuous evaluation of the bio-membrane was carried out under standard conditions in order to determine the membrane half-life without losing its efficiency in the electrochemical cell. These experiments were performed in triplicate in different solutions; results obtained in the electrolyzer cell are displayed in Table 1.  
In all cases the potential obtained was lower to the one observed with the untreated membrane; this behavior is expected, and it helps minimize the energy used to promote the formation of H2 and O2. Ion mobility was found to depend on the applied treatment (Table 1).  
Immersion treatment is considered a gentle treatment for the _Agave salmiana_ bio-membrane and for all studied media, and was considered an easy, economical treatment. The removal of water-soluble layers was attempted with this treatment at different concentrations of protons; however, there might be some water-soluble cuticle layers that may be altering the proper opening of stomata leading to a decreased ion mobility. Therefore, the bio-membrane lifetime did not increase significantly [35; 36].  
A similar behavior was observed for the clean-up treatment with the organic solvents. This process, with the exception of the methanol treatment, removes waxes that promote the opening of stomata, and causes conductivity values to increase in comparison with the ones obtained with the non-treatment bio-membrane. Clean-up treatments cause the bio-membrane dehydration and its easy fracture in a single use, which explains its shorter useful life [37].  
Polymeric coating with Nafion increases the electrical resistance compared to the non-treated bio-membrane, due to the obstruction of the bio-membrane channels, which generates a temperature increment leading to a separation of the polymeric phase from the bio-membrane. However, with these two phases, the life time increases.  
Mechanical treatment is the simplest and fastest; it significantly decreases the required potential and its electrical resistance, placing itself as a good treatment option. Nevertheless, the associated lifetime does not increase significantly compared to the non-treated bio-membrane, since for this treatment the bio-membrane is submitted to mechanical.  
The thermal treatment bio-membrane was the best option among all evaluated treatments. The results obtained are competitive to these obtained with commercial membranes. This membrane minimizes the potential (2.0 volts) required to separate the elements from water, and it also reduces the electrical resistance, promoting a higher mobility of the ions (conductivity of 10 mS cm\({}^{-1}\)) which is similar to other already reported membranes such as: Alginate bio-membrane and Nafion membrane [11; 34; 31]. It is also worth mentioning that the half-life of the thermally-treated bio-membrane remained in good condition even after two weeks of continuous use. Considering that ion mobility is the main performance factor, the best performing bio-membrane is the thermally-treated one, which reached the highest ion mobility values