Considerable worldwide interest exists in discovering renewable energy sources that can substitute for fossil fuels. Lignocellulosic biomass, the most abundant and inexpensive renewable feedstock on the planet, has a great potential for sustainable production of fuels, chemicals, and carbon-based materials. Fast pyrolysis integrated with hydrotreating, one of the simplest, most cost-effective, and most efficient processes to convert lignocellulosic biomass to liquid hydrocarbon fuels for transportation, has attracted significant attention in recent decades. However, effective hydrotreating of pyrolysis bio-oil presents a daunting challenge to the commercialization of biomass conversion via pyrolysis-hydrotreating. Specifically, the development of active, selective, and stable hydrotreating catalysts is problematic due to the poor quality of current pyrolysis bio-oil feedstock (i.e., high oxygen content, molecular complexity, coking propensity, and corrosiveness). Significant research has been conducted to address the practical issues and provide fundamental understanding of hydrotreating and hydrodeoxygenation (HDO) of bio-oils and their oxygen-containing model compounds, including phenolics, furans, and carboxylic acids. A wide range of catalysts have been studied, including conventional Mo-based sulfide catalysts and noble metal catalysts. Noble metal catalysts have been the primary focus of recent research because of their excellent catalytic performances and because they do not require the use of environmentally unfriendly sulfur. Recently, the reaction mechanisms of the HDO of model compounds on noble metal catalysts and their efficacy for hydrotreating or stabilization of bio-oil have been reported. This review provides a survey of relevant literature, published over the past decade, reporting advances in the understanding of the HDO chemistry of bio-oils and their model compounds, mainly on noble metal catalysts.

Sustainable energy generation calls for a shift away from centralized, high-temperature, energy-intensive processes to decentralized, low-temperature conversions that can be powered by electricity produced from renewable sources. Electrocatalytic conversion of biomass-derived feedstocks would allow carbon recycling of distributed, energy-poor resources in the absence of sinks and sources of high-grade heat. Selective, efficient electrocatalysts that operate at low temperatures are needed for electrocatalytic hydrogenation (ECH) to upgrade the feedstocks. For effective generation of energy-dense chemicals and fuels, two design criteria must be met: (i) a high H:C ratio via ECH to allow for high-quality fuels and blends and (ii) a lower O:C ratio in the target molecules via electrochemical decarboxylation/deoxygenation to improve the stability of fuels and chemicals. The goal of this review is to determine whether the following questions have been sufficiently answered in the open literature, and if not, what additional information is required: What organic functionalities are accessible for electrocatalytic hydrogenation under a set of reaction conditions? How do substitutions and functionalities impact the activity and selectivity of ECH? What material properties cause an electrocatalyst to be active for ECH? Can general trends in ECH be formulated based on the type of electrocatalyst? What are the impacts of reaction conditions (electrolyte concentration, pH, operating potential) and reactor types?

We show that the inductive electron-withdrawing effect of diphenylphosphoryl (Ph2PO) groups lowers both the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of a carbazole chromophore. This improves electron injection from a cathode without affecting the high triplet exciton energy (E T ≈ 3.0 eV) of the host material. Three new carbazole derivatives, 3,6-bis(diphenylphosphoryl)-9-ethylcarbazole (PO10), 3,6-bis(diphenylphosphoryl)-9-phenylcarbazole (PO9), and N-(4-diphenylphosphoryl phenyl) carbazole (MPO12), were investigated as host materials in blue phosphor-doped organic light-emitting devices (OLEDs). Photophysical characterization showed all three carbazole derivatives exhibit monomer UV fluorescence (367−385 nm) in solution and contributions from molecular aggregates or excimers in solid-state films (378−395 nm). The polar MPO12 derivative exhibited solvatochromism and had the highest propensity for aggregate formation in the solid state. Testing of OLEDs using PO9, PO10, and MPO12 as host materials for the sky blue organometallic phosphor iridium(III) bis(4,6-(difluorophenyl)-pyridinato-N,C 2′) picolinate (FIrpic) gave external quantum efficiencies (EQE) and operating voltages at a similar current density (J = 13 mA/cm2) of 6−8% at <7 V. The best device performance was exhibited using MPO12 as the host when an appropriate hole-blocking layer was implemented. The higher performance of MPO12 was attributed to the ambipolar charge-transporting character of the polar carbazole derivative. However, exciton relaxation on nonradiative aggregate states of all host materials studied may limit further improvements in device efficiencies.