Algae biomasses are considered a viable option for the production of biofuel because of their high yields of oil produced per dry weight. Brown macroalgae Sargassum spp. are one of the most abundant species of algae in the shores of Puerto Rico. Its availability in large quantity presents a great opportunity for use as a source of renewable energy. However, high ash content of macroalgae affects the conversion processes and the quality of resulting fuel products. This research studied the effect of different demineralization treatments of Sargassum spp. biomass, subsequent hydrothermal liquefaction (HTL), and bio-oil characterization. Demineralization constituted five different treatments: nanopure water, nitric acid, citric acid, sulfuric acid, and acetic acid. Performance of demineralization was evaluated by analyzing both demineralized biomass and HTL products by the following analyses: total carbohydrates, proteins, lipids, ash content, caloric content, metals analysis, Fourier transform infrared-attenuated total reflectance spectroscopy, energy dispersive spectroscopy, scanning electron microscopy, and GCMS analysis. HTL of Sargassum spp. before and after citric acid treatment was performed in a 1.8 L batch reactor system at 350°C with a holding time of 60 min and high pressures (5-21 MPa). Demineralization treatment with nitric acid was found the most effective in reducing the ash content of the macroalgae biomass from 27.46 to 0.99% followed by citric acid treatment that could reduce the ash content to 7%. Citric acid did not show significant leaching of organic components such as carbohydrates and proteins, and represented a less toxic and hazardous option for demineralization. HTL of untreated and citric acid treated Sargassum spp. resulted in bio-oil yields of 18.4 0.1 and 22.2 0.1% (ash-free dry basis), respectively. ± ±

Precise tuning of the electronic properties of Ag/C using under potentially deposited (UPD) Cu and subsequent galvanic displacement to deposit atomically dispersed loading of Pd resulted in a robust bimetallic alloy with significant activity for the oxygen reduction reaction in alkaline media. The specific design of the catalyst and atomic arrangement of Pd−Ag outperforms conventional Pd/C and Ag/C commercial catalysts. The ORR activity of Pd deposited onto Ag/C was determined on the basis of rotating disk electrode voltammetry studies, showing a 2-fold increase in Pd mass activities compared to results obtained using Pd/C. While scanning transmission electron microcopy (STEM) coupled with electron energy loss spectroscopy (EELS) probed the uniformity of the nanoparticles, the origin of the outstanding activity was traced to the structural properties of the Pd−Ag interface as shown by X-ray absorption spectroscopy (XAS), along with X-ray photoelectron spectroscopy (XPS). Segregation of metals with a suitable geometric arrangement of the Ag to Pd ratio at the interface resulted in an increased performance where the active sites were key steps of oxygen bond breaking.

We report a comprehensive quantitative study of the production of refined bio-crudes via a controlled hydrothermal liquefaction (HTL) process using Ulva fasciata macroalgae (UFMA) as biomass and ultrananocrystalline Fe3O4 (UNCFO) as catalyst. X-ray diffraction and electron microscopy were applied to elucidate the formation of the high-quality nanocatalysts. Gas chromatography-mass spectroscopy (GC-MS) and CHNS analyses showed that the bio-crude yield and carbon/oxygen ratios increase as the amount of UNCFO increases, reaching a peak value of 32% at 1.25 wt% (a 9% increase when compared to the catalyst-free yield). The bio-crude is mainly composed of fatty acids, alcohols, ketones, phenol and benzene derivatives, and hydrocarbons. Their relative abundance changes as a function of catalyst concentration. FTIR spectroscopy and vibrating sample magnetometry revealed that the as-produced bio-crudes are free of iron species, which accumulate in the generated bio-chars. Our findings also indicate that the energy recovery values via the HTL process are sensitive to the catalyst loading, with a threshold loading of 1.25 wt%. GC-MS studies show that the UNCFO not only influences the chemical nature of the resulting bio-crudes and bio-chars, but also the amount of fixed carbons in the solid residues. The detailed molecular characterization of the bio-crudes and bio-chars catalyzed by UNCFO represents the first systematic study reported using UFMA. This study brings forth new avenues to advance the highly-pure bio-crude production employing active, heterogeneous catalyst materials that are recoverable and recyclable for continuous thermochemical reactions.

The Rotating Disk Slurry Electrodeposition (RoDSE) technique is a novel method allowing to deposit electrochemically metal nanoparticles on a given conductive support and produce a powder catalyst for diverse applications, for example, ethanol oxidation reaction (EOR). This technique was used to electrodeposit Pd nanoparticles on carbon Vulcan XC-72R nanoflakes at three different applied potentials (0.0, 0.4, and 0.7 V vs. RHE). The potentials were chosen based on different regions of Pd electrodeposition on a clean glassy carbon electrode. Each Pd/Vulcan catalyst was characterized through different spectroscopic, microscopic, and electrochemical techniques. Powder X-ray diffraction and transmission electron microscopy studies verified the Pd crystallinity and particle size, respectively. The Pd particle size decreased with a more positive applied electrodeposition potential at carbon Vulcan XC-72R nanoflakes. X-ray photoelectron spectroscopy determined that the applied potential affected, both, the final palladium and carbon oxidation states. Finally, cyclic voltammetry was used to characterize the electrocatalytic activity of each Pd / Vulcan catalyst in 0.1M KOH and for the EOR. It was found that, for Pd electrodeposition, an applied potential of 0.4 V vs. RHE provided harmony between a mass transport and kinetically controlled deposition thereby providing the optimal conditions to produce a better catalyst with better EOR.