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Manganese oxide is an effective promoter for enhancing the activity and selectivity of cobalt-based Fischer-Tropsch synthesis (FTS) catalysts. Previous studies suggest that Co atoms located at the Co-MnO perimeter adsorb CO more strongly and undergo C-O bond cleavage more readily than CO adsorbed on Co sites, which leads to improved C5+ selectivity. Thus, direct characterization of the formation and structure of the active interface between Co nanoparticles and MnO is essential for a full understanding of the FTS promotion effect. Scanning transmission electron microscopic (STEM) methods are well-suited for direct characterization of nanoscale features through imaging, energy dispersive spectroscopy (EDS) elemental mapping, and spatially resolved electron diffraction, a technique known as scanning nanobeam diffraction. However, these techniques require that the catalytic nanoparticles are non-overlapping and well-defined, which is not typical for nanoparticles on porous metal oxide FTS supports. In the present study, we addressed these challenges by synthesizing catalysts composed of cobalt dispersed on nonporous alumina nanospheres (Co/ANS), which yielded isolated nanoparticles that are amenable to elemental and phase mapping by STEM-EDS and scanning nanobeam diffraction. Then, manganese oxide-promoted Co/ANS (Mn-Co/ANS) was characterized using these two techniques, which provided direct evidence for the transformation of a Co-Mn oxide spinel present in the as-prepared catalyst into closely associated Co3O4 and MnO2 nanoparticles in the passivated catalyst after its use for FTS.

Ni and nitrogen-doped carbons are selective catalysts for CO 2 reduction to CO (CO 2 R), but the hypothesized NiN x active sites are challenging to probe with traditional characterization methods. Here, we synthesize 61 Ni-enriched model catalysts, termed 61 NiPACN, in order to apply 61 Ni Mössbauer spectroscopy using synchrotron radiation ( 61 Ni-SR-MS) to characterize the structure of these atomically dispersed NiN x sites. First, we demonstrate that the CO 2 R results and standard characterization techniques (SEM, PXRD, XPS, XANES, EXAFS) point to the existence of dispersed Ni active sites. Then, 61 Ni-SR-MS reveal significant internal magnetic fields of ∼5.4 T, which is characteristic of paramagnetic, high-spin Ni 2+ , in the 61 NiPACN samples. Finally, theoretical calculations for a variety of Ni-N x moieties confirm that high-spin Ni 2+ is stable in non-planar, tetrahedrally distorted geometries, which results in calculated isotropic hyperfine coupling that is consistent with 61 Ni-SR-MS measurements.

Bridging polymer design with catalyst surface science is a promising direction for tuning and optimizing electrochemical reactors that could impact long-term goals in energy and sustainability. Particularly, the interaction between inorganic catalyst surfaces and organic-based ionomers provides an avenue to both steer reaction selectivity and promote activity. Here, we studied the role of imidazolium-based ionomers for electrocatalytic CO 2 reduction to CO (CO 2 R) on Ag surfaces and found that they produce no effect on CO 2 R activity yet strongly promote the competing hydrogen evolution reaction (HER). By examining the dependence of HER and CO 2 R rates on concentrations of CO 2 and HCO 3 - , we developed a kinetic model that attributes HER promotion to intrinsic promotion of HCO 3 - reduction by imidazolium ionomers. We also show that varying the ionomer structure by changing substituents on the imidazolium ring modulates the HER promotion. This ionomer-structure dependence was analyzed via Taft steric parameters and density functional theory calculations, which suggest that steric bulk from functionalities on the imidazolium ring reduces access of the ionomer to both HCO 3 - and the Ag surface, thus limiting the promotional effect. Our results help develop design rules for ionomer-catalyst interactions in CO 2 R and motivate further work into precisely uncovering the interplay between primary and secondary coordination in determining electrocatalytic behavior.

Understanding the differences between reactions driven by elevated temperature or electric potential remains challenging, largely due to materials incompatibilities between thermal catalytic and electrocatalytic environments. We show that Ni, N-doped carbon (NiPACN), an electrocatalyst for the reduction of CO 2 to CO (CO 2 R), can also selectively catalyze thermal CO 2 to CO via the reverse water gas shift (RWGS) representing a direct analogy between catalytic phenomena across the two reaction environments. Advanced characterization techniques reveal that NiPACN likely facilitates RWGS on dispersed Ni sites in agreement with CO 2 R active site studies. Finally, we construct a generalized reaction driving-force that includes temperature and potential and suggest that NiPACN could facilitate faster kinetics in CO 2 R relative to RWGS due to lower intrinsic barriers. This report motivates further studies that quantitatively link catalytic phenomena across disparate reaction environments., (© 2021 Wiley-VCH GmbH.)

In situ characterization of electrochemical systems can provide deep insights into the structure of electrodes under applied potential. Grazing-incidence X-ray diffraction (GIXRD) is a particularly valuable tool owing to its ability to characterize the near-surface structure of electrodes through a layer of electrolyte, which is of paramount importance in surface-mediated processes such as catalysis and adsorption. Corrections for the refraction that occurs as an X-ray passes through an interface have been derived for a vacuum-material interface. In this work, a more general form of the refraction correction was developed which can be applied to buried interfaces, including liquid-solid interfaces. The correction is largest at incidence angles near the critical angle for the interface and decreases at angles larger and smaller than the critical angle. Effective optical constants are also introduced which can be used to calculate the critical angle for total external reflection at the interface. This correction is applied to GIXRD measurements of an aqueous electrolyte-Pd interface, demonstrating that the correction allows for the comparison of GIXRD measurements at multiple incidence angles. This work improves quantitative analysis of d-spacing values from GIXRD measurements of liquid-solid systems, facilitating the connection between electrochemical behavior and structure under in situ conditions.

Background and Aims: Minimally invasive and robotic surgeries need lesser fluid replacement but the role of restricted fluids in robotic surgeries other than prostatic surgeries has not been clearly defined. Our primary aim was to evaluate the effects of a restrictive fluid regimen versus a liberal policy on intra-operative lactate in robotic colorectal surgery. Secondary outcomes were need for vasopressors, extubation on table, post-operative renal functions and length of ICU (LOICU) stay., Methods: American society of anaesthesiologists (ASA) physical status I-II patients scheduled for robot-assisted colorectal surgery were randomised into one of two groups, receiving either 2 mL/kg/h (Group R) or 4mL/kg/h, (group L). Fluid boluses of 250 ml were administered if mean arterial pressure (MAP) <65 mmHg or urine output <0.5 ml/kg/h. Norepinephrine was added for the blood pressure after 2 fluid boluses. Surgical field was assessed by modified Boezaart's scale and surgeon satisfaction by Likert scale., Results: Demographics and baseline renal functions were comparable. Adjusted intra-operative lactate at 2 h, 4 h, and 6 h and need for noradrenaline and post-operative creatinine were similar. One patient in the group L was ventilated due to hypothermia. The field was better at the 4 h in group R and comparable at other time points. The LOICU stay was longer in Group L., Conclusion: The use of restrictive fluid strategy of 2 mL/kg/h (group R) does not increase lactate levels or creatinine, improves surgical field at 4 h and shortens ICU stay in comparison to a liberal 4 mL/kg/h (group L) in robotic colorectal surgery., Competing Interests: There are no conflicts of interest., (Copyright: © 2020 Indian Journal of Anaesthesia.)

Ni,N-doped carbon catalysts have shown promising catalytic performance for CO 2 electroreduction (CO 2 R) to CO; this activity has often been attributed to the presence of nitrogen-coordinated, single Ni atom active sites. However, experimentally confirming Ni-N bonding and correlating CO 2 reduction (CO 2 R) activity to these species has remained a fundamental challenge. We synthesized polyacrylonitrile-derived Ni,N-doped carbon electrocatalysts (Ni-PACN) with a range of pyrolysis temperatures and Ni loadings and correlated their electrochemical activity with extensive physiochemical characterization to rigorously address the origin of activity in these materials. We found that the CO 2 R to CO partial current density increased with increased Ni content before plateauing at 2 wt % which suggests a dispersed Ni active site. These dispersed active sites were investigated by hard and soft X-ray spectroscopy, which revealed that pyrrolic nitrogen ligands selectively bind Ni atoms in a distorted square-planar geometry that strongly resembles the active sites of molecular metal-porphyrin catalysts., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three-dimensional hierarchical porous carbon materials with flower-like superstructures are of great interest for energy applications since their unique shape not only provides high accessible surface area and consequently more exposed active sites but also facilitates ion transport for high-rate capability. However, finding a controllable way to make porous carbons with such specific shapes has been challenging. Herein, we report a tunable and simple method for one-pot synthesis of polyacrylonitrile and its copolymer nanostructured particles with various superstructures (flower, pompom, hairy leave, and petal shapes) controlled by employing various solvents or by the incorporation of different co-monomers. The correlation between polymer particle shapes and solvent properties has been identified through Hansen solubility parameters analysis. The obtained uniform polyacrylonitrile particles could be readily converted into porous carbons by high-temperature gas treatment while maintaining the original shape of the polymer precursor structures. The resulting carbon materials have high nitrogen-doping concentration (7-15 at%) and tunable porous structures. This novel synthetic method provides a simple way to make porous carbons with controllable morphology and potentially advantageous properties for a variety of potential energy and environmental applications, such as electrochemical energy conversion and wastewater treatment.

A group-contribution method based on scaled-particle theory was developed to predict Henry's constants for six families of persistent organic pollutants: polychlorinated benzenes, polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polychlorinated naphthalenes, and polybrominated diphenyl ethers. The group-contribution model uses limited experimental data to obtain group-interaction parameters for an easy-to-use method to predict Henry's constants for systems where reliable experimental data are scarce. By using group-interaction parameters obtained from data reduction, scaled-particle theory gives the partial molar Gibbs energy of dissolution, Δg̅ 2 , allowing calculation of Henry's constant, H 2 , for more than 700 organic pollutants. The average deviation between predicted values of log H 2 and experiment is 4%. Application of an approximate van't Hoff equation gives the temperature dependence of Henry's constants for polychlorinated biphenyls, polychlorinated naphthalenes, and polybrominated diphenyl ethers in the environmentally relevant range 0-40 °C.

Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3-20 vol % Au are found to have an elastic modulus of ∼6-19 GPa, and hardness of ∼120-170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.