Perovskites are of great interest as replacements for precious metals and oxides used in bifunctional air electrodes involving the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). ...Herein, we report the synthesis and activity of a phase-pure nanocrystal perovskite catalyst that is highly active for the OER and ORR. The OER mass activity of LaNiO3, synthesized by the calcination of a rapidly dried nanoparticle dispersion and supported on nitrogen-doped carbon, is demonstrated to be nearly 3-fold that of 6 nm IrO2 and exhibits no hysteresis during oxygen evolution. Moreover, strong OER/ORR bifunctionality is shown by the low total overpotential (1.02 V) between the reactions, on par or better than that of noble metal catalysts such as Pt (1.16 V) and Ir (0.92 V). These results are examined in the context of surface hydroxylation, and a new OER cycle is proposed that unifies theory and the unique surface properties of LaNiO3.
Perovskite oxides have attracted significant attention as energy conversion materials for metal-air battery and solid-oxide fuel-cell electrodes owing to their unique physical and electronic ...properties. Amongst these unique properties is the structural stability of the cation array in perovskites that can accommodate mobile oxygen ions under electrical polarization. Despite oxygen ion mobility and vacancies having been shown to play an important role in catalysis, their role in charge storage has yet to be explored. Herein we investigate the mechanism of oxygen-vacancy-mediated redox pseudocapacitance for a nanostructured lanthanum-based perovskite, LaMnO3. This is the first example of anion-based intercalation pseudocapacitance as well as the first time oxygen intercalation has been exploited for fast energy storage. Whereas previous pseudocapacitor and rechargeable battery charge storage studies have focused on cation intercalation, the anion-based mechanism presented here offers a new paradigm for electrochemical energy storage.
The ventral hippocampus (vHPC), medial prefrontal cortex (mPFC), and basolateral amygdala (BLA) are each required for the expression of anxiety-like behavior. Yet the role of each individual element ...of the circuit is unclear. The projection from the vHPC to the mPFC has been implicated in anxiety-related neural synchrony and spatial representations of aversion. The role of this projection was examined using multi-site neural recordings combined with optogenetic terminal inhibition. Inhibition of vHPC input to the mPFC disrupted anxiety and mPFC representations of aversion, and reduced theta synchrony in a pathway-, frequency- and task-specific manner. Moreover, bilateral, but not unilateral, inhibition altered physiological correlates of anxiety in the BLA, mimicking a safety-like state. These results reveal a specific role for the vHPC-mPFC projection in anxiety-related behavior and the spatial representation of aversive information within the mPFC.
•The vHPC-mPFC pathway is required for normal anxiety-like behavior•Anxiety-related increases in vHPC-mPFC theta synchrony require direct vHPC-mPFC input•Spatial representations of aversion in the mPFC are dependent on direct vHPC input•The effects of inhibition of vHPC inputs are task, pathway, and frequency specific
Padilla-Coreano et al. use optogenetic inhibition and multi-site neurophysiology to demonstrate pathway- and frequency-specific effects of inhibiting ventral hippocampal input to the medial prefrontal cortex. Terminal inhibition reduced anxiety-like behavior, theta synchrony, and spatial representations of aversion within the cortex.
The ability to design and characterize uniform, bimetallic alloy nanoparticles, where the less active metal enhances the activity of the more active metal, would be of broad interest in catalysis. ...Herein, we demonstrate that simultaneous reduction of Ag and Pd precursors provides uniform, Ag-rich AgPd alloy nanoparticles (∼5 nm) with high activities for the oxygen reduction reaction (ORR) in alkaline media. The particles are crystalline and uniformly alloyed, as shown by X-ray diffraction and probe corrected scanning transmission electron microscopy. The ORR mass activity per total metal was 60% higher for the AgPd2 alloy relative to pure Pd. The mass activities were 2.7 and 3.2 times higher for Ag9Pd (340 mA/mgmetal) and Ag4Pd (598 mA/mgmetal), respectively, than those expected for a linear combination of mass activities of Ag (60 mA/mgAg) and Pd (799 mA/mgPd) particles, based on rotating disk voltammetry. Moreover, these synergy factors reached 5-fold on a Pd mass basis. For silver-rich alloys (Ag≥4Pd), the particle surface is shown to contain single Pd atoms surrounded by Ag from cyclic voltammetry and CO stripping measurements. This morphology is favorable for the high activity through a combination of modified electronic structure, as shown by XPS, and ensemble effects, which facilitate the steps of oxygen bond breaking and desorption for the ORR. This concept of tuning the heteroatomic interactions on the surface of small nanoparticles with low concentrations of precious metals for high synergy in catalytic activity may be expected to be applicable to a wide variety of nanoalloys.
Urea electrooxidation has attracted considerable interest as an alternative anodic reaction in the electrochemical generation of hydrogen due to both the lower electrochemical potential required to ...drive the reaction and also the possibility of eliminating a potentially harmful substance from wastewater during hydrogen fuel production. Nickel and nickel-containing oxides have shown activities comparable to those of precious-metal catalysts for the electrooxidation of urea in alkaline conditions. Herein, we investigate the use of nanostructured LaNiO3 perovskite supported on Vulcan carbon XC-72 as an electrocatalyst. This catalyst exhibits an exceptionally high mass activity of ca. 371 mA mgox –1 and specific activity of 2.25 A mg–1 cmox –2 for the electrooxidation of urea in 1 M KOH, demonstrating the potential applications of Ni-based perovskites for direct urea fuel cells and low-energy hydrogen production. While LaNiO3 is shown to be stable at low overpotentials, through in-depth mechanistic studies the catalyst surface was observed to restructure and there was apparent CO2 poisoning of the LaNiO3 upon extended cycling, a result that may be extended to other Ni-based systems.
The impact of employee productivity on real estate investment trust (REIT) performance is examined. Using a sample of U.S. equity REITs from 2003 to 2017, we first estimate parameters of a firm‐level ...production function correcting for endogenous input choices. The coefficient for labor input is statistically significant, indicating that labor productivity is an important component of overall REIT productivity. More importantly, REIT operating efficiency and financial performance are found to be negatively correlated with previous‐year employee instability (a proxy for employee turnover), but positively correlated with several lagged employee productivity measures, suggesting that a stable, motivated workforce improves a REIT's operating efficiency and performance. These findings suggest that employees play an important role in REIT operations and that managing employees properly and creating an effective corporate culture are essential to REIT performance.
Relations between Real Estate Investment Trust (REIT) efficiency and operational performance, risk, and stock return are examined. REIT-level operational efficiency is measured as the ratio of ...operational expenses to revenue, where a higher operational efficiency ratio (OER) indicates a less efficient REIT. For a sample of U.S. equity REITs from the modern REIT era, operational performance, measured by return on assets (ROA) as well as return on equity (ROE), is negatively associated with previous-year operational efficiency ratios, which suggests that more efficient REITs generate better operating results. Results further show that more efficient REITs have lower levels of credit risk and total risk. Perhaps most important, empirical evidence shows that the cross-sectional stock return of REITs is partially explained by operational efficiency and that a portfolio consisting of highly efficient REITs earns, on average, a higher cumulative stock return than a portfolio consisting of low efficiency REITs.
We present a series of perovskite electrocatalysts that are highly active for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in an aqueous alkaline electrolyte. ...Lanthanum-based perovskites containing different transition metal active sites (LaBO3, B = Ni, Ni0.75Fe0.25, Co, Mn) are synthesized by a general colloidal method, yielding phase pure catalysts of homogeneous morphology and surface area (8–14 m2/g). Each perovskite’s ability to catalyze the OER and ORR is examined using thin film rotating disk electrochemistry (RDE). LaCoO3 supported on nitrogen-doped carbon is shown to be ∼3 times more active for the OER than high-surface-area IrO2. Furthermore, LaCoO3 is demonstrated to be highly bifunctional by having a lower total overpotential between the OER and ORR (ΔE = 1.00 V) than Pt (ΔE = 1.16) and Ru (ΔE = 1.01). The OER and ORR pathways are perturbed by the introduction of peroxide disproportionation functionality via support interactions and selective doping of the catalyst. LaNi0.75Fe0.25O3’s ability to disproportionate peroxide is hypothesized to be responsible for the ∼50% improvement over LaNiO3 in catalytic activity toward the ORR, despite similar electronic structure. These results allow us to examine the pathways for OER and ORR in context of support interactions, transition metal redox processes, and catalytic bifunctionality.
The existing literature documents a clear relation between public school quality and a residential real estate price premium. The literature on whether charter school availability and quality are ...associated with a price premium, however, is surprisingly thin. After controlling for public school quality, we provide evidence that residential real estate price premiums are associated with charter school availability and quality. The price premium is smaller than that of quality public schools, but is economically meaningful when the quality of charter schools exceeds the quality of public schools. The price premium associated with charter schools is more prominent in areas where a large percentage of the population is between the ages of 6 and 18 and for family‐oriented housing types. We also show that the premium associated with quality charter schools varies with school type and is highest for high schools. The findings contribute to the literature on school quality with policy implications relating to school choice options such as charter schools and vouchers.
Abstract
The electrolysis of water is of global importance to store renewable energy and the methodical design of next-generation oxygen evolution catalysts requires a greater understanding of the ...structural and electronic contributions that give rise to increased activities. Herein, we report a series of Ruddlesden–Popper La
0.5
Sr
1.5
Ni
1−
x
Fe
x
O
4±
δ
oxides that promote charge transfer via cross-gap hybridization to enhance electrocatalytic water splitting. Using selective substitution of lanthanum with strontium and nickel with iron to tune the extent to which transition metal and oxygen valence bands hybridize, we demonstrate remarkable catalytic activity of 10 mA cm
−2
at a 360 mV overpotential and mass activity of 1930 mA mg
−1
ox
at 1.63 V via a mechanism that utilizes lattice oxygen. This work demonstrates that Ruddlesden–Popper materials can be utilized as active catalysts for oxygen evolution through rational design of structural and electronic configurations that are unattainable in many other crystalline metal oxide phases.
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