SELECTIVE ELECTROCATALYTIC OXIDATION OF GLYCEROL ON BIMETALLIC ANODE CATALYSTS IN ANION EXCHANGE MEMBRANE FUEL CELLS

摘要

Glycerol will be massively obtained as a byproduct of blooming biodiesel production, therefore, it has potential to serve as a main building block molecule for future productions of higher-valued oxygenated chemicals.1 We will present our recent research on selective oxidation of glycerol on precious metal- transitional metal bimetallic anode catalysts in anion exchange membrane fuel cells (AEMFCs). A solution phase reduction method was developed to prepare Pt, Pd, Au and their bimetallic catalysts, such as PtNi, PtCo, PtV, PtFe nanoparticles, PtFe, PdFe-nanowires (NW) with small diameter of 2-5 nm.3-8 The single AEMFC with non-PGM cathode and the self-prepared anode catalysts have demonstrated high output electrical power density. As shown in Fig.1, the AEMFC with 1.0 mg/cm2 FeCu-N4/C cathode catalyst and 1.0 mg/cm2 Pt/C anode catalyst has shown a peak power density over 145 mW/cm2 at 80oC and 2 atm backpressure of O2, This peak power density remains 98 mW/cm2 even at a very low loading of 0.1 mgPt/cm2, this represents 30-40 times and 2-3 orders of magnitude higher than the proton exchange membrane fuel cells (with high PtRu and Pt catalyst loadings of >8mg/cm2) and state-of-the-art biofuel cells (with enzymatic catalysts), respectively. We found that the fuel cell operation voltage (anode overpotential) is able to regulate the oxidation product distributions. Pt and its bimetallic catalysts exhibited different selectivity to glyceric acid, tartronic acid, glycolic acid, and oxalic acid products. PtM bimetallic catalysts favors production of glyceric acid with high selectivity. The electrocatalytic oxidation of glycerol on these catalysts was also studied in both a three-electrode-cell and an electrolysis cell, and the detailed oxidation mechanistic steps in high pH media will be presented.