Effect of phosphorus on the physicochemical and electrochemical properties of Ni/Carbon electrodes for glycerol electrooxidation

In this study, the influence of phosphorus doping on the electrocatalytic activity of glycerol-based carbon-supported nickel towards glycerol electrooxidation is investigated. The P-doped and un-doped glycerol-based carbon are synthesized through dehydration using phosphoric acid and thermal treatment, respectively. The P-doped catalysts with different Ni loadings (names as P-carbon_Ni (200), P-carbon_Ni (400), and P-carbon_Ni (600)) and the un-doped catalyst; carbon_Ni (600) are analysed for their physicochemical properties, which indicate that P-doping can enhance the electrocatalytic activities of the fabricated electrodes. The scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analyses reveal the higher porosity of P-carbon_Ni (600) relative to the un-doped carbon_Ni (600) and a uniform distribution of the doped elements. The cyclic voltammetric studies show that the un-doped carbon_Ni (600) possesses a smaller electrochemical surface area (98.49 cm2) and a poor surface coverage with -OH (6.35 x 10-5 mol/cm2) when compared to P-carbon_Ni (600) whose electrochemical surface area and surface coverage with -OH are 115.49 cm2 and 7.62 x 10-5 mol/cm2, respectively. Undoubtedly, the electrocatalytic performance of P-carbon_Ni (600) for glycerol oxidation is much better than the un-doped carbon_Ni (600), as also revealed by chronoamperometry and electrochemical impedance studies. P-carbon_Ni (600) is able to stabilize at higher current density, as the electrooxidation of glycerol progresses, and possesses a lower charge transfer resistance indicating that the incorporation of phosphorus into glycerol-based carbon enhances the conductivity of glycerol-based carbon-supported nickel. Furthermore, the HPLC analysis of the bulk electrolysis of glycerol after 15,000 seconds shows 100% glycerol conversion.