Evaluation of most efficient redox couple based on compatibility of donor–acceptor in photogalvanic cell for simultaneous solar power conversion and storage

Abstract

• To evaluate the most efficient redox (dye-reductant combination) couple based on compatibility of electron donor (reductant) and acceptor (dye) species for the PG cell. • The photogalvanic study for four (BCB-fructose, BCB-AA, MB-fructose and MB-AA) redox systems has been done, simultaneously. The order for redox couple based on electrical output is: MB-AA > MB-fructose > BCB-AA > BCB-fructose. • The electrical output is high when MB is used as a photosensitizer with both fructose and AA. It may be because of the larger λ max and the low molecular weight of MB than BCB. • The literature photogalvanic data for the different dye-AA systems clearly indicate that the electrical output has a lower than MB-AA redox couple of present study. • Thus, for the PG cell, the MB-AA redox couple has highest compatibility for electron acceptor and donor out of four redox systems. There are several devices for direct conversion of solar energy to electric energy, but, all have zero storage capacity. Photogalvanic cell (PG) has both properties to convert and store (chemical form) the solar energy. Therefore, the PG cells may be playing a very important role to fulfill energy demand in the future. Here, our aim is to evaluate the most efficient redox (dye-reductant combination) couple based on the compatibility of the donor (reductant) and acceptor (dye) species for the PG cell. For this, we have completed photogalvanics (measurement and calculation of different electrical parameters of each cell) for brilliant cresyl blue (BCB) or methylene blue (MB)-fructose/ascorbic acid (AA) redox couple for solar power conversion and storage. Here, MB/BCB and fructose/AA have been used as photosensitizers and reductants, respectively. Results show the order for redox couple based on electrical output is: MB-AA > MB-fructose > BCB-AA > BCB-fructose. The electrical output is high when MB is used as a photosensitizer with both fructose and AA. It may be because of the larger λ max and the low molecular weight of MB than BCB. Indeed, the generation of electricity in the PG cell is the outcome of the diffusion process of molecules or ions in an electrolytic solution. The results reported in the literature for the different dye-AA systems of the PG cells clearly indicate that the electrical output of every system has a lower value as compared to the MB-AA redox couple of present study. Hence, MB-AA is the most efficient and stable system out of the four redox couples. Thus, the dye and reductant having structures like MB and AA are more compatible for electron acceptor and donor power in the PG cell for simultaneous solar power conversion and storage in the PG cell.