Rain water was collected from Noakhali, Bangladesh after two days of rain. All chemicals (copper sulphate, sulphuric acid, hydrochloric acid and sodium chloride) used in this study were purchased from MERCK, Germany. Aluminium sheet and Copper wire for electrodes were purchased from local market.

Water for different purposes has its own requirements as to composition and purity. Hence, water quality assessment involves analysis of physical, chemical, biological and microbiological parameters. Here, the physical parameters such as pH, electric conductivity, salinity, total dissolved solid (TDS) of rain water were analyzed and tabulated in Table 1.

Result shows that rain water possesses tolerable pH and salinity. Mean value of conductivity (0.4 mS/cm) and TDS (22 ppm) indicates that rain water contains less interfering particles responsible for lowering the efficiency of the cell, as it is evident that conductivity decreased with TDS [16] and TDS decrease the cell efficiency.

TDS = 765 . 1EC l .0 87 (2)

Four different electrode combinations were used for electrolysis of NaCl solution (Figure 2).

Result shows that, Cu(Al)-Al combination of electrodes showed higher hydrogen

production rate than three other electrodes combination. These electrodes combination can be arranged in the order of increasing rate of hydrogen production as:

Al–Al < Cu(Al)–Cu(Al) < Al–Al < Cu(Al)–Al

Maximum hydrogen production (0.130 mol/hr) was found when rain water was electrolysed by Cu(Al)-Al electrode combination. Al-Al electrodes held the second position (0.116 mol/hr). Whereas, Cu(Al)-Cu(Al) didn’t give satisfactory rate and Al-Cu(Al) gave least value of production rate (0.040 mol/hr).

Cu(Al)-Al electrode acted as the most sensitive electrode combination. It can be best described by the basic knowledge of electrical properties of aluminium and copper. Conductivity of pure copper at 20˚C, 5.96 × 10⁷ S/m [17] is much higher than the conductivity of pure aluminium, 3.77 × 10⁷ S/m at 20˚C [18]. It is seen that, copper coating on aluminium increase the conductivity of this hybrid material as happened to copper clad aluminium wire [19]. According to Elektrisola Group, a renowned enameled wire manufacturing company, the conductivity of their product CCA15% (15% Copper Clad Aluminium) is 3.915 × 10⁷ S/m, slightly higher than pure aluminium [20]. For this reason, there arises an innate potential difference between anode and cathode compared to the rest of the electrode combinations in this study. This potential difference is responsible for the maximum production rate at this condition.

A greater number of effective ionic collisions per unit time were occurred by increasing electrolytic concentration and as a result reaction rate as well as efficiency increased with increasing electrolytic concentration [5]. A number of studies suggest that, hydrogen production rate increase with the strength of electrolyte used [21] [22].

In this study concentration of electrolyte was gradually varied from 0.034 to 0.086 M and consequently hydrogen production rate increased linearly with electrolyte concentration. HPR (0.131 mol/hr) found maximum for 0.086 M and similarly efficiency found 16% for the highest concentration of electrolyte (Table 2 & Figure 3).

It is well established that HPR efficiency increases with temperature [23]. Current study analysed temperature effect on electrolysis of 0.051 M aqueous solution of NaCl and found that HPR increased with temperature, tabulated in Table 3. At room temperature efficiency measured 11% but it rose sharply up to 29% at 60˚C. Ionic conductivity of an electrolyte rises directly with rising temperature. When temperature is high, less energy is required to reach any given current density compared to low temperature process. Moreover, surface reaction of any electrolyte was also directly affected by changing temperature [5]. The more the temperature, the surface reaction of electrolytes would be more appreciable. Hence, temperature was the most important variables on the electrolytic cell.