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Sodium-containing batteries have the potential to address many of the challenges faced in the ongoing development of enhanced energy storage devices. Sodium is inexpensive and earth abundant, and aprotic Na−O2 batteries, in particular, have gravimetric energy densities significantly exceeding those of Li-ion devices. However, poor functional cell lifespans present a significant obstacle to the development of Na−O2 cells, with parasitic side reactions involving the NaO2 discharge products, leading to a rapid decline in cell performance. These parasitic reactions are hypothesized to occur through two main pathways: (i) deleterious dissolution of NaO2 into the electrolyte during periods of cell idling and (ii) disproportionation of NaO2 in the near-surface region to form Na-rich species (Na1+xO2) on the cathode. To formulate practical strategies to suppress these processes, in turn, the development of fundamental, molecular-level mechanistic understanding is essential. In this contribution, such mechanistic insights are elucidated by coupling density functional theory calculations with experimental observations to study the surface chemistry of the NaO2 discharge product. First, a series of ab initio surface phase diagrams are constructed to determine the structure of the NaO2 surfaces under realistic operating conditions, whereby an inverse relationship between surface coordination and surface energy is determined. Next, a molecular surface dissolution analysis is performed for the identified surface terminations, demonstrating a further inverse relationship between surface energy and the thermodynamic barrier for dissolution. Finally, a study of the thermodynamics of thin-film formation of sodium oxides over the NaO2 discharge product is carried out and suggests that an electrochemical reduction reaction, rather than an inherent chemical disproportionation, forms the observed Na-rich species in the near-surface region under high discharge overpotentials. From these insights, we suggest future studies that may yield practical design changes to improve stability and extend the lifespan of Na−O2 batteries. 

Sodium-containing batteries have the potential to address many of the challenges faced in the ongoing development of enhanced energy storage devices. Sodium is inexpensive and earth abundant, and aprotic Na−O2 batteries, in particular, have gravimetric energy densities significantly exceeding those of Li-ion devices. However, poor functional cell lifespans present a significant obstacle to the development of Na−O2 cells, with parasitic side reactions involving the NaO2 discharge products, leading to a rapid decline in cell performance. These parasitic reactions are hypothesized to occur through two main pathways: (i) deleterious dissolution of NaO2 into the electrolyte during periods of cell idling and (ii) disproportionation of NaO2 in the near-surface region to form Na-rich species (Na1+xO2) on the cathode. To formulate practical strategies to suppress these processes, in turn, the development of fundamental, molecular-level mechanistic understanding is essential. In this contribution, such mechanistic insights are elucidated by coupling density functional theory calculations with experimental observations to study the surface chemistry of the NaO2 discharge product. First, a series of ab initio surface phase diagrams are constructed to determine the structure of the NaO2 surfaces under realistic operating conditions, whereby an inverse relationship between surface coordination and surface energy is determined. Next, a molecular surface dissolution analysis is performed for the identified surface terminations, demonstrating a further inverse relationship between surface energy and the thermodynamic barrier for dissolution. Finally, a study of the thermodynamics of thin-film formation of sodium oxides over the NaO2 discharge product is carried out and suggests that an electrochemical reduction reaction, rather than an inherent chemical disproportionation, forms the observed Na-rich species in the near-surface region under high discharge overpotentials. From these insights, we suggest future studies that may yield practical design changes to improve stability and extend the lifespan of Na−O2 batteries. 

Significant emphasis has been placed recently in engineering the catalytic environment beyond the active site for tuning the activity, selectivity, and stability of supported metal catalysts for targeted reactions. The environment around the active site in supported catalysts can be modified by introducing multi-dimensionality through alloying, encapsulation, and surface bound ligands. In this Review, we provide a summary of synthesis strategies that have enabled the design of multifunctionality and multidimensionality in heterogeneous supported catalysts. We specifically discuss alloys, encapsulated/inverted catalytic structures, and ligand capped metal nanoparticle systems. We highlight the effects on catalyst activity, selectivity and stability that arise from modifying the neighboring two-dimensional environment through alloying or three-dimensional environment through encapsulation with porous inorganic films or surface organic moieties. We conclude by providing a short perspective on the promises and remaining challenges associated with engineering the local environment around the active sites of supported heterogeneous catalysts. 

Solid oxide electrolysis cells (SOECs) are promising for the selective electrochemical conversion of CO 2 , or mixed streams of CO 2 and H 2 O, into high energy products such as CO and H 2 . However, these systems are limited by the poor redox stability of the state-of-the-art Ni-based cathode electrocatalysts. Due to their favorable redox properties, mixed ionic-electronic conducting (MIEC) oxides have been considered as promising alternatives. However, improvement of the electrochemical performance of MIEC-based SOEC electrocatalysts is needed and requires an understanding of the factors that govern their activity. Herein, we investigate the effect of B-site 3 d metal cations (Cr, Fe, Co, Ni) of LaBO 3 perovskites on their CO 2 electrochemical reduction activity in SOECs. We find that their electrochemical performance is highly dependent on the nature of the B-site cation and trends as LaFeO 3 > LaCoO 3 > LaNiO 3 > LaCrO 3 . Among these perovskites, LaNiO 3 is the least stable and decomposes under electrochemical conditions. In situ characterization and ab initio theoretical calculations suggest that both the nature of the B-site cation and the presence of oxygen surface vacancies impact the energetics of CO 2 adsorption and reduction. These studies provide fundamental insights critical toward devising ways to improve the performance of MIEC-based SOEC cathodes for CO 2 electroreduction. 

In this study, we present an investigation aimed at characterizing and understanding the synergistic interactions in encapsulated catalytic structures between the metal core ( i.e. , Pd) and oxide shell ( i.e. , TiO 2 , ZrO 2 , and CeO 2 ). Encapsulated catalysts were synthesized using a two-step procedure involving the initial colloidal synthesis of Pd nanoparticles (NPs) capped by various ligands and subsequent sol–gel encapsulation of the NPs with porous MO 2 (M = Ti, Zr, Ce) shells. The encapsulated catalytic systems displayed higher activity than the Pd/MO 2 supported structures due to unique physicochemical properties at the Pd–MO 2 interface. Pd@ZrO 2 exhibited the highest catalytic activity for CO oxidation. Results also suggested that the active sites in Pd encapsulated by an amorphous ZrO 2 shell structure were significantly more active than the crystalline oxide encapsulated structures at low temperatures. Furthermore, CO DRIFTS studies showed that Pd redispersion occurred under CO oxidation reaction conditions and as a function of the oxide shell composition, being observed in Pd@TiO 2 systems only, with potential formation of smaller NPs and oxide-supported Pd clusters after reaction. This investigation demonstrated that metal oxide composition and (in some cases) crystallinity play major roles in catalyst activity for encapsulated catalytic systems. 

Atmospheric NO₂is of great concern due to its adverse effects on human health and the environment, motivating research on NO₂detection and remediation. Existing low-cost room-temperature NO₂sensors often suffer from low sensitivity at the ppb level or long recovery times, reflecting the trade-off between sensor response and recovery time. Here, we report an atomically dispersed metal ion strategy to address it. We discover that bimetallic PbCdSe quantum dot (QD) gels containing atomically dispersed Pb ionic sites achieve the optimal combination of strong sensor response and fast recovery, leading to a high-performance room-temperature p-type semiconductor NO₂sensor as characterized by a combination of ultra–low limit of detection, high sensitivity and stability, fast response and recovery. With the help of theoretical calculations, we reveal the high performance of the PbCdSe QD gel arises from the unique tuning effects of Pb ionic sites on NO₂binding at their neighboring Cd sites.

 

Hydrodeoxygenation chemistries play a key role in the upgrading of biomass‐derived feedstocks. Among these, the removal of targeted hydroxyl groups through selective C−O bond cleavage from molecules containing multiple functionalities over heterogeneous catalysts has shown to be a challenge. Herein, we report a highly selective and stable heterogeneous catalyst for hydrodeoxygenation of tartaric acid to succinic acid. The catalyst consists of reduced Mo⁵⁺centers promoted by palladium, which facilitate selective C−O bond cleavage, while leaving intact carboxylic acid end groups. Stable catalytic performance over multiple cycles is demonstrated. This catalytic system opens up opportunities for selective processing of biomass‐derived sugar acids with a high degree of chemical functionality.