Conversion of the greenhouse gas carbon dioxide (CO2) to value-added products is an important challenge for sustainable energy research, and nanomaterials offer a broad class of heterogeneous catalysts for such transformations. Here we report a molecular surface functionalization approach to tuning gold nanoparticle (Au NP) electrocatalysts for reduction of CO2 to CO. The N-heterocyclic (NHC) carbene-functionalized Au NP catalyst exhibits improved faradaic efficiency (FE = 83%) for reduction of CO2 to CO in water at neutral pH at an overpotential of 0.46 V with a 7.6-fold increase in current density compared to that of the parent Au NP (FE = 53%). Tafel plots of the NHC carbene-functionalized Au NP (72 mV/decade) vs parent Au NP (138 mV/decade) systems further show that the molecular ligand influences mechanistic pathways for CO2 reduction. The results establish molecular surface functionalization as a complementary approach to size, shape, composition, and defect control for nanoparticle catalyst design.

SO A 2– (A = 3–4; B–) functionalities are anchored on metal oxides used to catalyze NH3-assisted selective NO X reduction (SCR) for a SO2-bearing feed gas stream. SO A 2– species act as conjugate bases of Brönsted acidic bonds (B––H+) and modifiers of redox sites (M(n–1)+–O–), both of which are combined to dictate the activities of SCR (−r NOX ) and ammonium (bi) sulfate (AS/ABS) poison degradation (−r AS/ABS) at low temperatures. Nonetheless, their pathways have been barely clarified and underexplored, while questioning catalytic significance of mono-dentate or bi-dentate SO A 2– species in dominating −r NOX and −r AS/ABS. While using Sb-promoted MnV2O6 as a reservoir of SO A 2– functionalities with distinct binding arrays, elementary stages for the SCR and AS/ABS degradation were proposed, thermodynamically assessed, and analyzed using kinetic control runs in tandem with density functional theory calculations. These allowed for the conclusions that the reaction stage between B––H+•••NH3•••O––M(n–1)+ and gaseous NO and the liberation stage of H2O/SO2 from B–•••H2O•••SO2•••H2O via dissociative desorption are endothermic and dominate −r NOX and −r AS/ABS as the rate-determining steps of the SCR and AS/ABS degradation, respectively. In addition, mono-dentate and bi-dentate SO A 2– species are verified central in directing −r NOX and −r AS/ABS by elevating collision frequency between B––H+•••NH3•••O––M(n–1)+ and NO and declining the energy barrier required for dissociative H2O/SO2 desorption for the SCR and AS/ABS degradation, respectively. In particular, mono-dentate SO A 2– functionalities can improve the overall redox trait of the surface, thereby substantially promoting its low-temperature SCR performance under a SO2-excluding feed gas stream. Meanwhile, bi-dentate SO A 2– functionalities can slightly improve the overall redox trait of the surface, yet, can readily degrade AS/ABS by accelerating the endothermic fragmentation of S2O7 2– innate to ammonium pyrosulfate, while compensating for the moderate efficiency in fragmenting NH4 + of ammonium pyrosulfate via Eley–Rideal-type SCR. This can significantly elevate the SCR performance of the bi-dentate SO A 2–-containing surface under a SO2-including feed gas stream alongside with the promotion of its long-term stability at low temperatures. These can be adaptable and exploited in discovering/amending a host of metal oxides (or vanadates) imperatively functionalized with SO A 2– or poisoned with AS/ABS under low thermal energies.

Low detection sensitivity stemming from the weak polarization of nuclear spins is a primary limitation of magnetic resonance spectroscopy and imaging. Methods have been developed to enhance nuclear spin polarization but they typically require high magnetic fields, cryogenic temperatures or sample transfer between magnets. Here we report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field magnetic resonance. The technique harnesses the high optically induced spin polarization of diamond nitrogen vacancy centres at room temperature in combination with dynamic nuclear polarization. We observe bulk nuclear spin polarization of 6%, an enhancement of ∼170,000 over thermal equilibrium. The signal of the hyperpolarized spins was detected in situ with a standard nuclear magnetic resonance probe without the need for sample shuttling or precise crystal orientation. Hyperpolarization via optical pumping/dynamic nuclear polarization should function at arbitrary magnetic fields enabling orders of magnitude sensitivity enhancement for nuclear magnetic resonance of solids and liquids under ambient conditions.

No abstract

No abstract

No abstract

NO 3 • can compete with omnipotent • OH/SO 4 •– in decomposing aqueous pollutants because of its lengthy lifespan and significant tolerance to background scavengers present in H 2 O matrices, albeit with moderate oxidizing power. The generation of NO 3 • , however, is of grand demand due to the need of NO 2 • /O 3 , radioactive element, or NaNO 3 /HNO 3 in the presence of highly energized electron/light. This study has pioneered a singular pathway used to radicalize surface NO 3 – functionalities anchored on polymorphic α-/γ-MnO 2 surfaces (α-/γ-MnO 2 -N), in which Lewis acidic Mn 2+/3+ and NO 3 – served to form • OH via H 2 O 2 dissection and NO 3 • via radical transfer from • OH to NO 3 – ( • OH → NO 3 • ), respectively. The elementary steps proposed for the • OH → NO 3 • route could be energetically favorable and marginal except for two stages such as endothermic • OH desorption and exothermic • OH-mediated NO 3 – radicalization, as verified by EPR spectroscopy experiments and DFT calculations. The Lewis acidic strength of the Mn 2+/3+ species innate to α-MnO 2 -N was the smallest among those inherent to α-/β-/γ-MnO 2 and α-/γ-MnO 2 -N. Hence, α-MnO 2 -N prompted the rate-determining stage of the • OH → NO 3 • route ( • OH desorption) in the most efficient manner, as also evidenced by the analysis on the energy barrier required to proceed with the • OH → NO 3 • route. Meanwhile, XANES and in situ DRIFT spectroscopy experiments corroborated that α-MnO 2 -N provided a larger concentration of surface NO 3 – species with bi -dentate binding arrays than γ-MnO 2 -N. Hence, α-MnO 2 -N could outperform γ-MnO 2 -N in improving the collision frequency between • OH and NO 3 – species and in facilitating the exothermic transition of NO 3 – functiona...

Despite the enormous potential shown by recent biorefineries, the current bioeconomy still encounters multifaceted challenges. To develop a sustainable biorefinery in the future, multidisciplinary research will be essential to tackle technical difficulties. Herein, we leveraged a known plant genetic engineering approach that results in aldehyde-rich lignin via down-regulation of cinnamyl alcohol dehydrogenase (CAD) and disruption of monolignol biosynthesis. We also report on renewable deep eutectic solvents (DESs) synthesized from phenolic aldehydes that can be obtained fromCADmutant biomass. The transgenicArabidopsis thaliana CADmutant was pretreated with the DESs and showed a twofold increase in the yield of fermentable sugars compared with wild type (WT) upon enzymatic saccharification. Integrated use of low-recalcitrance engineered biomass, characterized by its aldehyde-type lignin subunits, in combination with a DES-based pretreatment, was found to be an effective approach for producing a high yield of sugars typically used for cellulosic biofuels and biobased chemicals. This study demonstrates that integration of renewable DES with plant genetic engineering is a promising strategy in developing a closed-loop process.