Exploratory insight into the effect of salt and radical scavengers on the photo‐galvanic dye degradation: A spectroscopic approach

Abstract Dye‐sensitizer based photo‐galvanic cells' electrolyte suffers efficiency loss due to photo‐induced dye‐degradation mediated by radical intermediates based chain reaction mechanism. This study employs spectral analysis to investigate how various salts/radical scavengers (like Na 2 SO 4 ) mitigate this dye‐degradation. Pure dye solution has been found to show absorbance of 3.0 in visible region ( λ max ~510 nm). Other constituents (i.e., other than dye) of electrolyte has been found to decrease absorbance. The electrolytic solution (without scavenger/salts) shows lower absorbance at ~518 nm, with absorbance decreasing to zero and becoming negative beyond ~630 nm. In present research, Na 2 SO 4 has been explored with anticipation of playing most effective role in quenching the radical intermediates leading to subsequent inhibition of dye‐degradation. Increasing Na 2 SO 4 salt in SPADNS dye‐based electrolyte has been found to decrease photo‐galvanic cell's electrical output, i.e., the power ~ 5119.4 μW (half‐change time, t 1/2 , 6 min) obtained in absence of Na 2 SO 4 salt dropped to ~3978.24 μW ( t 1/2 , 4 min) and ~ 3362.24 μW ( t 1/2 , 4 min) in presence of 0.1 gm Na 2 SO 4 salt and 0.3 g Na 2 SO 4 salt, respectively. This suggests that increasing scavenger amount is unfavorable for photo‐galvanic power. Contrary to expectations, the Na 2 SO 4 salt decreased cell's electrical output. In addition to quenching of radicals detrimental to dye species, the scavenger is also likely to destroy the photo‐galvanically useful electro‐active energy rich dye radical species, leading to lower efficiency. Therefore, using scavengers to ensure dye stability may not be suitable for photo‐galvanic systems under studied experimental conditions.