Navigating glycerol electrochemical oxidation roadmap and catalyst selection.

Herein, we study the effect of adding bismuth to Ni-nanostructured catalysts (Ni x Bi1–x , x = 100–90 at. %) for glycerol electro-oxidation in alkaline solution by combining physiochemical, electrochemical, and in situ infrared spectroscopy techniques, as well as continuous electrolysis with HPLC (high-performance liquid chromatography) product analysis. The addition of small quantities of Bi (<20 at. %) to Ni nanoparticles led to significant activity enhancement at lower overpotentials, with Ni90Bi10 displaying an over 2-fold increase compared to Ni. Small quantities of bismuth actively affected the reaction selectivity of Ni by suppressing the pathways with C–C bond cleavage, hindering the production of carbonate and formate and improving the formation of tartronate, oxalate, and glycerate. Furthermore, the effect of aging on Ni x Bi1–x catalysts was investigated, resulting in structural modification from the Ni–Bi double shell/core structure to Bi decorated on the folded Ni sheet, thus enhancing their activity twice after 2 weeks of aging. NiBi catalysts are promising candidates for glycerol valorization to high-value-added products.

Glycerol partial electrooxidation was studied on Ni x Pd1–x (x = 100, 95, 90, and 80 atom %) nanoparticles synthesized using a polyol method. The shape-controlled urchin-like monometallic Ni and spherical Ni x Pd1–x catalysts were synthesized. The morphology, crystal structure, and composition of Ni-rich catalysts were characterized using a number of physicochemical techniques. Detailed electrochemical characterizations showed that Ni and Ni x Pd1–x NPs are active for GEOR and that the reaction follows either the direct electron transfer mechanism at low glycerol concentrations or the indirect electron transfer mechanism at high concentration. Among all investigated electrocatalysts, Ni80Pd20 exhibited the highest current density at lower overpotentials due to both a synergetic effect of Ni and Pd and the smaller particle size of Ni80Pd20. In situ polarization modulation infrared-reflection absorption spectroscopy (PM-IRRAS) at various anodic potentials allowed discriminating the reaction products and intermediates directly on the electrode surface and in the electrolyte solution. PM-IRRAS showed that the main reaction products on Ni x Pd1–x are glyceraldehyde, carbonyl groups for mesoxalate and tartronate ions, carboxylate ions, and traces of carbon dioxide. Ni x Pd1–x catalysts are promising anode materials for glycerol oxidation to value added products and could be potentially combined with cathodic hydrogen production or CO2 electro-reduction processes in alkaline media.

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Benzalkonium chloride (BAC) is a key ingredient in many cleaning and disinfectant products due to it being an effective antiviral and biocidal agent. Because of its prolific use, especially following the recent global COVID pandemic, increased levels of BAC have been found in the environment, in particular, in wastewater, where it has negative impacts due to its toxicity. This necessitates an effective treatment for BAC in wastewater to reduce its toxicity. In this work, electrochemical oxidation of BAC on a boron‐doped diamond anode was studied to successfully remove BAC. The electrochemical measurements performed at different current densities confirmed that BAC was completely oxidized within 20 min of treatment at 50 mA/cm2. However, chemical oxygen demand (COD) measurements showed that around 50% of the initial BAC was completely mineralized after 1 h of degradation at 50 mA/cm2, while the remaining electrooxidation of BAC resulted in the production of transformation products.

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