Electrolyte selection toward efficient photoelectrochemical glycerol oxidation on BiVO 4 .

Glycerol, a primary by-product of biodiesel production, can be oxidized into various value-added chemicals, significantly enhancing the techno-economic value of photoelectrochemical (PEC) cells. Several studies have explored various photoelectrode materials and co-catalysts, but the influence of electrolytes on PEC glycerol oxidation has remained relatively unexplored despite its significance. Here, we explore the impact of various acidic (pH = 2) electrolytes, namely NaNO 3 , NaClO 4 , Na 2 SO 4 , K 2 SO 4 , and KP i , on PEC glycerol oxidation using nanoporous thin film BiVO 4 as a model photoanode. Our experimental findings reveal that the choice of electrolyte anion and cation significantly affects the PEC performance ( i.e. , photocurrent, onset potential, stability, and selectivity towards value-added products) of BiVO 4 for glycerol oxidation. To explain this interesting phenomenon, we correlate the observed performance trend with the ion specificity in the Hofmeister series as well as the buffering capacity of the electrolytes. Notably, NaNO 3 is identified as the optimal electrolyte for PEC glycerol oxidation with BiVO 4 when considering various factors such as stability and production rates for glycerol oxidation reaction (GOR) products, surpassing the previously favored Na 2 SO 4 . Glycolaldehyde emerges as the most dominant product with ∼50% selectivity in NaNO 3 . The general applicability of our findings is confirmed by similar observation in electrochemical (EC) GOR with a polycrystalline platinum anode. Overall, these results emphasize the critical role of electrolyte selection in enhancing the efficiency of EC/PEC glycerol oxidation.