Electrolysis of glycerol to value-added chemicals in alkaline media

BACKGROUND: Glycerol, a by-product of biodiesel production, is produced in large quantities, exceeding its demand. The saturation of glycerol resulted in a sharp reduction in its market value and the surplus waste may pose a risk to the environment. By means of electrochemical technologies, glycerol could be oxidized into value-added products such as glycerate, tartronate and lactate. In the present work, carbon-supported NiBi catalysts with different atomic ratios (NixBi1-x/C, wherex = 100, 95, 90 and 50 at%) were fabricated and utilized in a 25 cm(2) electrolysis cell. RESULTS: The as-fabricated catalysts were characterized and analyzed by various physicochemical and electrochemical characterizations. Using a three-electrode electrochemical cell, Ni95Bi5/C showed the highest current density of 104 mA cm(-2), with an onset potential of 1.32 V versus a reversible hydrogen electrode. Long-term chronoamperometry was performed in a glycerol electrolysis cell accompanied by the product analysis using high-performance liquid chromatography. It was found that Ni95Bi5/C had higher selectivity to glycerate C-3 product compared to Ni/C. Additionally, optimizing experimental conditions (applied potential, residence time and temperature) to achieve higher selectivity to C-3 products was thoroughly studied. The selectivity to C-3 value-added products was enhanced by adjusting the operating conditions. CONCLUSION: Small addition of bismuth to Ni/C enhanced both catalytic activity and selectivity to C-3 products. The main products formed on NixBi1-x/C were formate and glycerate, while the secondary products were glycolate, tartronate, oxalate and lactate. By running electrolysis under optimal conditions, the selectivity to C-3 products was significantly enhanced. (c) 2022 Society of Chemical Industry (SCI).

Automated summary

This study fabricated carbon-supported NiBi catalysts with different atomic ratios and used electrochemical technologies to oxidize glycerol into value-added products such as glycerate. By optimizing experimental conditions, the selectivity to C-3 value-added products was significantly enhanced.