Using algae as an renewable energy source for ethanol fuel cell and biofuel applications.

Abstract

Based on the search for new biodegradable materials, low cost and easy to synthesize by environmentally friendly methods, we report the use of carrageenan membranes (mixture of κ and λ carrageenans) with different concentrations of titanium dioxide nanoparticles (TiO₂ NPs) and Ni/CeO₂ (10 wt % Ni) for the fabrication of a novel fuel cell electrode for the oxidation of ethanol. Due to its high conductivity values, the CR5% membrane was mixed with Ni/CeO₂ to prepare the working electrode for cyclic voltammetry measurements. Using a solution of 1 M ethanol and 1 M KOH the oxidation of ethanol over CR5% + Ni/CeO₂ resulted in peak current density values at forward and reverse scan voltages of 9.52 mA/cm² and 12.22 mA/cm², respectively. From our results, the CR5% + Ni/CeO₂ shows to be more efficient in the oxidation of ethanol compared with commercially available Nafion membranes containing Ni/CeO₂. Also, we have developed a novel biodegradable κ-carrageenan (KC) and boron nitride (BN) nanoparticle membrane, optimized with ammonium sulfate (NHS). Our findings reveal that the KC/BN/NHS1% membrane achieves an exceptional ionic conductivity of 7.82x10^-5 S/cm, as determined by Impedance Spectroscopy (IS). If incorporating this membrane with a Ni/CeO₂ catalyst could have substantial potential in proton exchange applications for fuel cells, marking a crucial step forward in the quest for environmentally friendly fuel cell technologies. The properties of the developed membrane composite suggest potential broader applications in areas such as sensor technology, water purification, and environmentally responsive packaging. This underscores the critical role of nanotechnology in enhancing the functional versatility and sustainability of energy materials, propelling forward the development of green technology solutions. On the other hand, we studied the production of refined biocrude oils by a controlled hydrothermal liquefaction (HTL) process using the macroalga <em>Ulva fasciata</em> as biomass, and Ni/CeO₂ and NiZrO₂ as catalyst. Gas chromatography-mass spectroscopy (GC-MS) analyses show that the biocrude yield depends on type catalyst using. The number of compound changes depending on the type of catalyst Ni/CeO₂ or NiZrO₂. Biocrude is mainly composed of fatty acids, alcohols, phenol and benzene derivatives, and hydrocarbons. The DSC and TGA measurement show that oxidation of fatty acid around 200 ºC, reaching a higher enthalpy of 154.4 J/g for the Ni/CeO₂-treated biocrude, together with the combustion around 400 ºC of polycyclic aromatic hydrocarbons and benzene derivatives. FTIR shows the principle functional groups like alkyl groups, alcohols, ketones, aldehydes, carboxylic acids, alkene groups and fats. This study brings forth new avenues to advance the highly pure bio-crude production employing active, heterogeneous catalyst materials that are recoverable.