Dihydroxyacetone
(DHA) and glyceraldehyde (GA)the simplest
monosaccharides in natureare both essential building blocks
in organic synthesis. There have been detailed investigations on the
selective production of DHA and GA through the platinum-catalyzed
electrochemical oxidation of glycerol, which is a surplus byproduct
from biodiesel. However, less attention has been paid to the electrochemical
behavior of DHA and GA themselves. Here, we report the electrochemical
reduction of DHA and GA at different pH on platinum and palladium
electrodes. Palladium exhibits a superior activity toward both the
dehydroxylation and hydrogenation of DHA and GA. Using online high-performance
liquid chromatography, we show that both DHA and GA display a two-step
reduction. In particular, DHA is reduced first to acetol and then
sequentially to acetone, while GA is first reduced to 3-hydroxypropionaldehyde
(3-HPA), followed by hydrogenation to 1,3-propanediol. The reduction
of both molecules is accompanied by a poisoning of the catalyst surface. In situ Fourier-transform infrared spectroscopy measurements
suggest adsorbed carbon monoxide as the poisoning species, resulting
from the dissociative adsorption of DHA and GA. Mechanistic reaction
pathways for both DHA and GA reduction are proposed and discussed.