Shape-Controlled Pathways in the Hydrogen Production from Ethanol Steam Reforming over Ceria Nanoparticles

Air-Promoted Light-Driven Hydrogen Production from Bioethanol over Core/Shell Cr2O3@GaN Nanoarchitecture

Light-driven hydrogen production from biomass derivatives offers a path towards carbon neutrality. It is often however operated with the limitations of sluggish kinetics and severe coking. Herein, a disruptive air-promoted strategy is explored for efficient and durable light-driven hydrogen production from ethanol over a core/shell Cr2O3@GaN nanoarchitecture. The correlative computational and experimental investigations show ethanol is energetically favorable to be adsorbed on the Cr2O3@GaN interface, followed by dehydrogenation toward acetaldehyde and protons by photoexcited holes. The released protons are then consumed for H2 evolution by photogenerated electrons. Afterward, O2 can be evolved into active oxygen species and promote the deprotonation and C-C cleavage of the key C2 intermediate, thus significantly lowering the reaction energy barrier of hydrogen evolution and removing the carbon residual with inhibited overoxidation. Consequently, hydrogen is produced at a high rate of 76.9 mole H2 per gram Cr2O3@GaN per hour by only feeding ethanol, air, and light, leading to the achievement of a turnover number of 266,943,000 mole H2 per mole Cr2O3 over a long-term operation of 180 hours. Notably, an unprecedented light-to-hydrogen efficiency of 17.6 % is achieved under concentrated light illumination. The simultaneous generation of aldehyde from ethanol dehydrogenation enables the process more economically promising.

Ethanol Coupling Reactions over MgO-Al2O3 Mixed Oxide-Based Catalysts for Producing Biofuel Additives

Catalytic conversion of ethanol to 1-butanol was studied over MgO-Al₂O₃ mixed oxide-based catalysts. Relationships between acid-base and catalytic properties and the effect of active metal on the hydrogen transfer reaction steps were investigated. The acid-base properties were studied by temperature-programmed desorption of CO₂ and NH₃ and by the FT-IR spectroscopic examination of adsorbed pyridine. Dispersion of the metal promoter (Pd, Pt, Ru, Ni) was determined by CO pulse chemisorption. The ethanol coupling reaction was studied using a flow-through microreactor system, He or H₂ carrier gas, WHSV = 1 gEtOH·gcat.-1·h-1, at 21 bar, and 200-350 °C. Formation and transformation of surface species under catalytic conditions were studied by DRIFT spectroscopy. The highest butanol selectivity and yield was observed when the MgO-Al₂O₃ catalyst contained a relatively high amount of strong-base and medium-strong Lewis acid sites. The presence of metal improved the activity both in He and H₂; however, the butanol selectivity significantly decreased at temperatures ≥ 300 °C due to acceleration of undesired side reactions. DRIFT spectroscopic results showed that the active metal promoted H-transfer from H₂ over the narrow temperature range of 200-250 °C, where the equilibrium allowed significant concentrations of both dehydrogenated and hydrogenated products.