Electrochemical Hydrogenation of Acetone to Produce Isopropanol Using a Polymer Electrolyte Membrane Reactor

Electrochemical hydrogenation (ECH) of acetone is a relatively new method to produce isopropanol. It provides an alternative way of upgrading bio-fuels with less energy consumption and chemical waste as compared to conventional methods. In this paper, Polymer Electrolyte Membrane Fuel Cell (PEMFC) hardware was used as an electrochemical reactor to hydrogenate acetone to produce isopropanol and diisopropyl ether as a byproduct. High current efficiency (59.7%) and selectivity (>90%) were achieved, while ECH was carried out in mild conditions (65 °C and atmospheric pressure). Various operating parameters were evaluated to determine their effects on the yield of acetone and the overall efficiency of ECH. The results show that an increase in humidity increased the yield of propanol and the efficiency of ECH. The operating temperature and power supply, however, have less effect. The degradation of membranes due to contamination of PEMFC and the mitigation methods were also investigated.

Enhanced electrooxidation of glucose at nano-chitosan-NiOOH modified GC electrode: fuel blends and hydrocarbon impurities

The current study addresses, for the first time, the promoting effect of some selected fuel blending components, such as methanol (MeOH), ethanol (EtOH) and acetaldehyde (ACTA), on the glucose electrooxidation at a nano-chitosan-NiOOH modified GC electrode (nano-CS-NiOOH/GC). Blending glucose with different molar ratios of MeOH, EtOH and ACTA results in a significant enhancement in the fuel utilization, NiOOH oxidation capacity and turnover number of oxidized glucose molecules compared to the pure fuels. For instance, the use of glucose fuel blends composed of 40% of glucose with 60% of either MeOH, EtOH and ACTA results in 10, 8 and 5 times higher glucose activity of the nano-CS-NiOOH/GC electrode compared to using glucose as a pure fuel, respectively. In addition, the nano-CS-NiOOH/GC electrode shows a higher tolerance towards chloride ions poisoning compared to the NiOOH/GC electrode. The existence of minute amounts of hydrocarbon impurities, such as acetonitrile stemming from degradation of fuel cell components, results in significant enhancement of the glucose electrooxidation at the nano-CS-NiOOH/GC. In contrast, the presence of any of those hydrocarbon impurities results in a significant decrease of the NiOOH/GC electrode activity indicating the essential role of chitosan. Chitosan is believed to improve the catalytic activity and durability via stabilizing the nickel oxyhydroxide phase (β-NiOOH), which may be active for the reaction.

Chlorobenzene Poisoning and Recovery of Platinum-Based Cathodes in Proton Exchange Membrane Fuel Cells

The platinum electrocatalysts found in proton exchange membrane fuel cells are poisoned both reversibly and irreversibly by air pollutants and residual manufacturing contaminants. In this work, the poisoning of a Pt/C PEMFC cathode was probed by a trace of chlorobenzene in the air feed. Chlorobenzene inhibits the oxygen reduction reaction and causes significant cell performance loss. The performance loss is largely restored by neat air operation and potential cycling between 0.08 V and 1.2 V under H₂/N₂ (anode/cathode). The analysis of emissions, in situ X-ray absorption spectroscopy and electrochemical impedance spectra show the chlorobenzene adsorption/reaction and molecular orientation on Pt surface depend on the electrode potential. At low potentials, chlorobenzene deposits either on top of adsorbed H atoms or on the Pt surface via the benzene ring and is converted to benzene (ca. 0.1 V) or cyclohexane (ca. 0 V) upon Cl removal. At potentials higher than 0.2 V, chlorobenzene binds to Pt via the Cl atom and can be converted to benzene (less than 0.3 V) or desorbed. Cl^- is created and remains in the membrane electrode assembly. Cl^- binds to the Pt surface much stronger than chlorobenzene, but can slowly be flushed out by liquid water.