Tuning selectivity toward three-carbon product of glycerol electrooxidation in borate buffer through manipulating borate/glycerol molar ratio.

[Display omitted] • In-situ Raman tracking NiOx surface evolution, especially for the broadening band around 900 – 1200 cm-1. • Enhancing catalytic activity and selectivity of 3-carbon product through borate-polyol chelate. • Controlling five-member or six-member ring complex formation by varying borate/glycerol ratio. • Effect of borate/glycerol ratio on tuning selective oxidation of primary or secondary alcohol group. Controlling selective glycerol electrooxidation towards the primary or secondary alcohol group, which enables obtained dihydroxyacetone or glyceraldehyde as the main product, is a challenge for an effective glycerol electrolysis system. In this work, we systematically investigated the protective effect of borate-glycerol complexes toward primary and secondary alcohol group oxidation during the glycerol electrooxidation process on NiO x catalyst in borate buffer (pH 9.2). The Raman spectroscopy and high-performance liquid chromatography results indicated that manipulating the borate/glycerol (B/G) ratio could affect selective oxidation towards primary or secondary alcohol group. Five-member ring complex was more likely to form in the electrolyte with the B/G ratio of 0.1, whereas six-member ring complex became more significant in the electrolyte with the B/G ratio of 1.5. The dominance of five- or six-member ring complex could enhance the favored adsorption of primary or secondary alcohol group, thus generating glyceraldehyde or dihydroxyacetone as the main product, respectively. The results in this study highlight the significance of electrolyte property on glycerol electrocatalysis, which is universally applicable to other transition metal electrocatalysts, enabling the development of a highly selective glycerol electrooxidation towards primary or secondary alcohol system at near-neutral pH level. [ABSTRACT FROM AUTHOR]