Electrocatalyst composite consisting of copper (Cu), nickel (Ni), molybdenum (Mo) phosphorus (P) was synthesized and evaluated for the electro-oxidation of glycerol. An autocatalytic chemical reaction technique in an aqueous media containing the component ions of the composite was used to synthesize the catalyst on an activated substrate. The electrocatalyst was characterized using scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD) and various electrochemical techniques, including Cyclic voltammetry (CV), Linear Sweep Voltammetry (LSV), Chronoamperometry and Electrochemical Impedance Spectroscopy (EIS). A combination of voltammetry and high-pressure liquid chromatography product analysis was used to evaluate the activity of the electrocatalyst towards glycerol oxidation. Use of a mixture of reducing agents, specific ratios of metal ions in solution, pH, oxygen content of the autocatalytic solution and temperature conditions were identified for codeposition of all four catalyst components. CV results showed that the composite catalyst as prepared was active for glycerol oxidation in alkaline media and the activity was comparable to that of Pt under similar conditions and better than mono- or bi-metallic combinations of the components. Tafel analysis of the LSV results indicated exchange current densities ranging from 0.18 – 0.6 mA cm-2 for different deposition times and Tafel slopes of 120 – 130 mV/decade. Constant potential oxidation of glycerol between 0.5 - 1.3V (vs. Ag/AgCl) on CuNiMoP/C catalyst showed that as prepared catalyst selectively favored the production of formic acid at the lower potentials. At intermediate potential of 0.9 V, glyceraldehyde/dihydroxyacetone (DHA) are favored while at 1.1 V tartronic acid and mesoxalic acid are the major products. At potentials higher than 1.1 V, competing parasitic reactions reduced the glycerol conversion and product yield. Glycerol conversion of 62% was achieved at 1.1 V compared to 3 – 38% with Pt catalyst under similar conditions. Rates of reaction, measured in terms of current density, were found to be low for potentials lower than 0.7 V. Constant potential oxidations at 0.7 V for three different 24-hour cycles showed catalyst deactivation from leaching of Cu. These results have potential importance in direct alkaline glycerol fuel cell applications.
Audience Take Away:
- Audience will learn and be able to use technique to synthesize multi-elemental (non-precious metal) electrocatalyst on most substrates including non-conductive substrates
- Learn about electrocatalyst that has comparable activity to Pt that can be used in direct glycerol fuel cell
- Results provide information to assist in the design of direct glycerol fuel cell.
- Provides information on the product selectivity for glycerol oxidation.