Direct and Indirect Electrooxidation of Glycerol to Value‐Added Products

In this work, different approaches for the direct and indirect electrooxidation of glycerol, a by‐product of oleochemistry and biodiesel production, for the synthesis of value‐added products and of intermediates for biofuel/electrofuel production, were investigated and compared. For the direct electrooxidation, metallic catalysts were used, whose surfaces were modified by promoters or second catalysts. Bi‐modified Pt electrodes (Pt( x )Bi( y )/C) served as model systems for promoter‐supported electrocatalysis, whereas IrO(2)‐modified RuO(2) electrodes were studied as catalyst combinations, which were compared under acidic conditions with the respective monometallic catalysts (Pt/C, RuO(2)/Ti, IrO(2)/Ti). Furthermore, inorganic halide mediators (chloride, bromide, iodide) and organic nitroxyl mediators (4‐oxo‐2,2,6,6‐tetramethyl‐piperidin‐1‐oxyl and 4‐acetamido‐2,2,6,6‐tetramethyl‐piperidin‐1‐oxyl) were evaluated for indirect electrooxidation. These different approaches were discussed regarding selectivity, conversion, and coulombic efficiency of the electrochemical glycerol oxidation.