Seawater as new renewable energy resource: Material characterization of the cell electrodes

Abstract

Seawater batteries is a useful device for an emergency application with the utilization of the abundant and accessible resources. Most of the small scale batteries that are studied and developed using seawater electrolyte as energy source are published without the report on the materials characterization that may affect the environment quality. Thus this study is focusing on the materials characterization of the electrodes tested for seawater battery. The study performed on carbon rods as a cathode, while magnesium (Mg) and zinc (Zn) are anodes for two different combinations of electrodes for battery cell system; Mg–C and Zn–C cells respectively. The Mg–C cell was able to produce almost constant voltage output up to 8 h which is 2.53 V to power up a small torchlight as a load, while Zn–C electrodes was only 0.90 V and unable to power up the same load. Materials characterization was conducted before and after the test in seawater electrolyte for 4 and 8 h of test duration by using SEM, EDX, and ICP-MS. The results obtained from SEM–EDX analysis showed a major changes on the Mg anode only where the pure Mg (100 at.%) has changed into new phases that identified as a phase containing the mixture of Mg (reduced to less than 4 at.%) with chlorine, oxygen and calcium after the test, while Zn anode and carbon electrode for both cell showed a slight formation of new phases. Based on the ICP-MS analysis on the tested seawater electrolyte, the Mg–C electrodes is considered safe to be used as compared to Zn–C because ICP-MS has recorded zinc particles content in the tested seawater electrolyte exceeded the standard amount of Zn in natural seawater after 8 h of the test duration. Although, the Mg content in natural seawater (215 ppm) has increased about 49% (320 ppm) after the test, but the amount is still considered low for a standard Mg content in natural seawater which is 1300 ppm. The study has proved that Mg can be used as a safe anode to be applied in a battery using seawater as a renewable energy source.