Abstract
A triple junction (3J) solar cell having 33% efficiency at one Sun condition is integrated with an electrolyzer containing Pt wire electrodes to study the effect of pH, temperature and low flux solar light on H-2 production from water. Results indicate that electrolyte conduction affects the rate of reaction mostly due to the large voltage at maximum power (V-mpp) of the PV-cell. Measurements are performed both indoors, under 100-500 mWcm(-2) insolation, and outdoors. Electrochemical impedance measurements indicate that the exchange current, j(i), depends largely on the electrolyte resistance, r (j(i) = (V-app-V-eq)/r); where V-app is applied voltage provided from the cell and V-eq is the equilibrium potential for water electrolysis (1.23 V). The small increase in the hydrogen production rate with temperature (E-a = 4.4 kJ mol(-1)) is largely because of the high V-app, where above 1.6 V the IV curve enters into the Tafel slope region. The maximum solar-to-hydrogen conversion efficiency (STH) outdoor is found to be about 16% under acidic conditions. The high V-mpp (2.5 V) of the PV cell compared to V-opp (1.7 V) makes the current at maximum power (I-mpp) the limiting factor.