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Renewable-energy-driven nitrate (NO3-) electroreduction to ammonia (NH3) (NERA) has been an attractive technology for decarbonizing NH3 production and wastewater treatment. Improving NERA efficiency requires electrocatalysts that are earth-abundant and show fantastic performance. Here we report a semiempirical activity descriptor of eg occupancy (of surface B-site cations) for identifying inexpensive perovskite oxides with extremely high efficacy toward NERA. We establish the descriptor by systematic investigations of more than 10 perovskite oxides. These investigations demonstrate that their intrinsic NERA activities display a volcano-shaped dependence on eg occupancy and the optimized intrinsic activities are accessible at near-1 eg occupancies. This could plausibly be attributed to the favorable overlaps between surface adsorbates and vertically-oriented eg orbitals. More importantly, utilizing this descriptor, we predict a highly active, selective, and durable NERA electrocatalyst with a composition of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF). Because of its close-to-1 eg occupancy (i.e. ∼ 1.2), the BSCF features a superior NH3 production rate of 0.12 g ⋅ h − 1 ⋅ mg cat. − 1 (Faradaic efficiency of 97.8%) that is at top of the volcano plot, and substantially outperforms most NERA electrocatalysts reported in literature. [ABSTRACT FROM AUTHOR]

Cu-oxide-based catalysts are promising for CO2 electroreduction (CO2RR) to CH4, but suffer from inevitable reduction (to metallic Cu) and uncontrollable structural collapse. Here we report Cu-based rock-salt-ordered double perovskite oxides with superexchange-stabilized long-distance Cu sites for efficient and stable CO2-to-CH4 conversion. For the proof-of-concept catalyst of Sr2CuWO6, its corner-linked CuO6 and WO6 octahedral motifs alternate in all three crystallographic dimensions, creating sufficiently long Cu-Cu distances (at least 5.4 Å) and introducing marked superexchange interaction mainly manifested by O-anion-mediated electron transfer (from Cu to W sites). In CO2RR, the Sr2CuWO6 exhibits significant improvements (up to 14.1 folds) in activity and selectivity for CH4, together with well boosted stability, relative to a physical-mixture counterpart of CuO/WO3. Moreover, the Sr2CuWO6 is the most effective Cu-based-perovskite catalyst for CO2 methanation, achieving a remarkable selectivity of 73.1% at 400 mA cm−2 for CH4. Our experiments and theoretical calculations highlight the long Cu-Cu distances promoting *CO hydrogenation and the superexchange interaction stabilizing Cu sites as responsible for the superb performance. Cu-oxide-based catalysts are promising for CO2 electromethanation but suffer from inevitable reduction and structural collapse. Here the authors report a Cu-based rock-salt-ordered double perovskite oxide with superexchange-stabilized long-distance Cu sites for efficient and stable CO2 methanation. [ABSTRACT FROM AUTHOR]

The combination of bioactive Zn‐2Mg alloy and additively manufactured porous scaffold is expected to achieve customizable biodegradable performance and enhanced bone regeneration. Herein, Zn‐2Mg alloy scaffolds with different porosities, including 40% (G‐40‐2), 60% (G‐60‐2), and 80% (G‐80‐2), and different unit sizes, including 1.5 mm (G‐60‐1.5), 2 mm (G‐60‐2), and 2.5 mm (G‐60‐2.5), are manufactured by a triply periodic minimal surface design and a reliable laser powder bed fusion process. With the same unit size, compressive strength (CS) and elastic modulus (EM) of scaffolds substantially decrease with increasing porosities. With the same porosity, CS and EM just slightly decrease with increasing unit sizes. The weight loss after degradation increases with increasing porosities and decreasing unit sizes. In vivo tests indicate that Zn‐2Mg alloy scaffolds exhibit satisfactory biocompatibility and osteogenic ability. The osteogenic ability of scaffolds is mainly determined by their physical and chemical characteristics. Scaffolds with lower porosities and smaller unit sizes show better osteogenesis due to their suitable pore size and larger surface area. The results indicate that the biodegradable performance of scaffolds can be accurately regulated on a large scale by structure design and the additively manufactured Zn‐2Mg alloy scaffolds have improved osteogenic ability for treating bone defects. [ABSTRACT FROM AUTHOR]

Despite the intriguing potential shown by Sn‐based perovskite oxides in CO2 electroreduction (CO2RR), the rational optimization of their CO2RR properties is still lacking. Here we report an effective strategy to promote CO2‐to‐HCOOH conversion of Sn‐based perovskite oxides by A‐site‐radius‐controlled Sn−O bond lengths. For the proof‐of‐concept examples of Ba1−xSrxSnO3, as the A‐site cation average radii decrease from 1.61 to 1.44 Å, their Sn−O bonds are precisely shortened from 2.06 to 2.02 Å. Our CO2RR measurements show that the activity and selectivity of these samples for HCOOH production exhibit volcano‐type trends with the Sn−O bond lengths. Among these samples, the Ba0.5Sr0.5SnO3 features the optimal activity (753.6 mA ⋅ cm−2) and selectivity (90.9 %) for HCOOH, better than those of the reported Sn‐based oxides. Such optimized CO2RR properties could be attributed to favorable merits conferred by the precisely controlled Sn−O bond lengths, e.g., the regulated band center, modulated adsorption/activation of intermediates, and reduced energy barrier for *OCHO formation. This work brings a new avenue for rational design of advanced Sn‐based perovskite oxides toward CO2RR. [ABSTRACT FROM AUTHOR]

Cobalt-based perovskite oxides have shown great potential in electrocatalysis, but their employment in boosting nitrate electroreduction (NO3ER) to ammonia is unexplored. Here we report an effective strategy to promote the NO3ER activity by tuning the A-site deficiencies of cobalt-based perovskite oxides. Using a (Ba0.5Sr0.5)1−xCo0.8Fe0.2O3−δ (x = 0, 0.05, 0.10, 0.15, and 0.20) series as proof-of-concept catalysts, we demonstrate that their NO3ER activity shows a volcano-type dependence on the x values, with the maximum point at x = 0.15. Among them, at −0.45 V (vs. RHE), (BS)0.85CF shows the highest activity (143.3 mg h−1 mgcat−1 or 0.86 mmol h−1 cm−2) and selectivity (97.9%) for ammonia, together with excellent stability (200 h), better than those of most reported NO3ER catalysts. These optimized NO3ER properties could be ascribed to the physicochemical properties being modulated by the A-site deficiencies, such as creating a moderate amount of oxygen vacancies and introducing a moderate distance between the band center and Fermi level. This work opens up a new avenue for rational design of advanced cobalt-based perovskite oxides for catalyzing NO3ER. [ABSTRACT FROM AUTHOR]