Further, being an anodic reaction, this process can be coupled with water reduction, for simultaneous hydrogen production, or other reduction reactions, e.g. CO2 reduction, biomassderived reduction reactions etc. A recent life-cycle assessment demonstrated that electrocatalytic conversion of crude glycerol to lactic acid at 32% liquid product distribution and 100 kg/hr production rate can result in a 57% reduction in global warming potential compared to the bio-and chemocatalytic processes, when combined with a low-carbonintensity grid . Further emission reduction is possible when the product selectivity towards lactic acid is improved, pointing out the direction for further development. Reports of lactic acid electrosynthesis are limited, as listed in Fig. . In most of the cases, the glycerol electrolysis has been performed in a static half-cell configuration rather than a continuous membrane-electrode-assembly (MEA) electrolysis system. However, to maximize the benefits of coupling anode and cathode reactions, the set up must be compatible within a single system with easy product separation and high mass transport, in which case MEA electrolysis cell operating in galvanostatic mode holds greater promise in transferring the research into upscaling devices than conventional H-cells. Besides, to be industrial relevant, the process current density needs to be relatively high (i.e. > 200 mA cm -2 ), and liquid product distribution towards lactic acid needs to exceed 60 % to be compatible with the conventional fermentation method. Reports falling into this area are rare. To date, only Yan et al. reported 80 % lactic acid selectivity in their recent works, yet the method for calculating the glycerol conversion rate and lactic acid selectivity need to be further validated to confirm the high selectivity. Herein, based on the previous studies, we have chosen to perform our glycerol electrolysis towards lactic acid and H2 co-production in a MEA cell, with a reaction rate of 20 mA cm -2 . Although the current density is a magnitude lower than practical industrial scale, the focus here is to achieve high lactic acid yield by designing the electrocatalyst structure and understanding the reaction mechanism. Engineering challenges towards scaling up will later be tackled with strategies such as constructing 3D electrode structure, selecting suitable anion-exchange membrane, and engineering the interface microenvironment, taking inspiration from the electrochemical CO2 reduction community. Fig. | Glycerol dual reaction pathway: dehydration vs. oxidation. Pt based electrocatalysts can effectively catalyze the glycerol → DHA (dihydroxyacetone) / GLAD (glyceraldehyde) step as well as the following oxidation steps. Previous studies have shown that the glycerol to lactic acid transformation is a combination of electrochemical deprotonationheterogeneous dehydrationhomogeneous solution phase reaction process, with several intermediate steps involved, as illustrated in red (top) in Fig. . Pt-based electrocatalysts are the most active in catalyzing the glycerol deprotonation step towards dihydroxyacetone and glyceraldehyde. Density functional theory (DFT) calculations have already established the reaction pathways and the factors controlling activity and product selectivity within glycerol (electro-) oxidation on Pt(111) and other metal surfaces. Subsequently, in a non-electrochemical solution phase step, it is possible to dehydrate DHA to lactic acid. However, at oxidising potentials on Pt, the dehydration pathway towards lactic acid is less favoured than the competing electrochemical oxidation process towards glyceric acid (shown in blue (bottom) in Fig. ). Therefore, it is essential to develop an effective strategy to promote the dehydration pathway suppressing the electrochemical oxidation pathway within electrochemical glycerol oxidation..