Unbiased Stable Photoelectrochemical Glycerol Oxidation on Hematite Photoanodes.

Photoelectrochemical glycerol oxidation reaction (PEC GOR) is considered as one of the promising strategies for obtaining high-value products and transforming solar energy to hydrogen. Herein, we report that a Ge/Zr co-doped FeO photoanode present an excellent and stable PEC performance for glycerol oxidation to formate (FA) product. The Ge and Zr co-doping synergistically reduce charge carrier recombination and enhance charge transfer kinetics of the photoanode, promoting the selectivity and Faradaic efficiency toward FA chemical. Further the deposition of NiFeB co-catalyst promotes the cleavage of C─C bonds in glycerol molecules while inhibiting oxygen evolution reaction and facilitating FA accumulation. Impressively, the unbiased PEC tandem configuration for glycerol oxidation was established for coupling NiFeB/Ge/Zr-FeO photoanode with Fe(Pt)-NC cathode, achieving a photocurrent density of ∼1.9 mA cm with continuously operation of 100 h. The bias-free device maintains FA selectivity of above 80% with an accumulation of 1683 µmol cm, representing the best PEC GOR performance toward high-value chemicals reported so far. The reaction mechanism was clarified through in situ characterization. This work provides new avenues for the sustainable solar-powered chemical synthesis of unbiased PEC systems with high selectivity and durability.