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Metal single atoms (SAs) anchored in carbon support via coordinating with N atoms are efficient active sites to oxygen reduction reaction (ORR). However, rational design of single atom catalysts with highly exposed active sites is challenging and urgently desirable. Herein, an anion exchange strategy is presented to fabricate Fe‐N4 moieties anchored in hierarchical carbon nanoplates composed of hollow carbon spheres (Fe‐SA/N‐HCS). With the coordinating O atoms are substituted by N atoms, Fe SAs with Fe‐O4 configuration are transformed into the ones with Fe‐N4 configuration during the thermal activation process. Insights into the evolution of central atoms demonstrate that the SAs with specific coordination environment can be obtained by modulating in situ anion exchange process. The strategy produces a large quantity of electrochemical accessible site and high utilization rate of Fe‐N4. Fe‐SA/N‐HCS shows excellent ORR electrocatalytic performance with half‐wave potential of 0.91 V (vs. RHE) in 0.1 M KOH, and outstanding performance when used in rechargeable aqueous and flexible Zn‐air batteries. The evolution pathway for SAs demonstrated in this work offers a novel strategy to design SACs with various coordination environment and enhanced electrocatalytic activity. [ABSTRACT FROM AUTHOR]

Oxygen vacancies‐enriched black TiO2 is one promising support for enhancing hydrogen evolution reaction (HER). Herein, oxygen vacancies enriched black TiO2 supported sub‐nanometer Pt clusters (Pt/TiO2‐OV) with metal support interactions is designed through solvent‐free microwave and following low‐temperature electroless approach for the first time. High‐temperature and strong reductants are not required and then can avoid the aggregation of decorated Pt species. Experimental and theoretical calculation verify that the created oxygen vacancies and Pt clusters exhibit synergistic effects for optimizing the reaction kinetics. Based on it, Pt/TiO2‐OV presents remarkable electrocatalytic performance with 18 mV to achieve 10 mA cm−2 coupled with small Tafel slope of 12 mV dec−1. This work provides quick synthetic strategy for preparing black titanium dioxide based nanomaterials. [ABSTRACT FROM AUTHOR]

The electronic structure of composites plays a critical role in photocatalytic conversion, whereas it is challenging to modulate the orbital for an efficient catalyst. Herein, we regulated the t2g orbital occupancy state of Ti to realize efficient CO2 conversion by adjusting the amount of photo‐deposited Cu in the Cu/TiO2 composite. For the optimal sample, considerable electrons transfer from the Cu d orbital to the Ti t2g orbital, as proven by X‐ray absorption spectroscopy. The Raman spectra results also corroborate the electron enrichment on the Ti t2g orbital. Further theoretical calculations suggested that the orbital energy of the Ti 3d orbital in TiO2 is declined, contributing to accepting Cu 3d electrons. As a result, the Cu/TiO2 composite exhibited an extremely high selectivity of 95.9 % for CO, and the productivity was 15.27 μmol g−1 h−1, which is almost 6 times that of the original TiO2. Our work provides a strategy for designing efficient photocatalysis as a function of orbital regulation. [ABSTRACT FROM AUTHOR]

A temperature‐controlled cation‐exchange approach is introduced to achieve a unique dual‐exsolution in perovskite La0.8Fe0.9Co0.1O3−δ where both CoFe alloy and Co metal are simultaneously exsolved from the parent perovskite, forming an alloy and metal co‐decorated perovskite oxide. Mossbauer spectra show that cation exchange of Fe atoms in CoFe alloy and Co cations in the perovskite is the key to the co‐existence of Co metal and CoFe alloy. The obtained composite exhibits an enhanced catalytic activity as Li‐O2 battery cathode catalysts with a specific discharge capacity of 6549.7 mAh g−1 and a cycling performance of 215 cycles without noticeable degradation. Calculations show that the combination of decorated CoFe alloy and Co metal synergistically modulated the discharge reaction pathway that improves the performance of Li‐O2 battery. [ABSTRACT FROM AUTHOR]

Exfoliation of non‐layered (structurally) bulk materials at the nanoscale is challenging because of the strong chemical bonds in the lattice, as opposed to the weak van der Waals (vdW) interactions in layered materials. We propose a top‐down method to exfoliate ϵ‐MnO2 nanosheets in a family of charge‐ordered La1−xAExMnO3 (AE=Ca, Sr, Ba) perovskites, taking advantage of the Jahn–Teller disproportionation effect of Mn3+ and bond‐strength differences. ϵ‐MnO2 crystallized into a nickel arsenide (NiAs) structure, with a thickness of 0.91 nm, displays thermal metastability and superior water oxidation activity compared to other manganese oxides. The exfoliation mechanism involves a synergistic proton‐induced Mn3+ disproportionation and structural reconstruction. The synthetic method could also be potentially extended to the exfoliation of other two‐dimensional nanosheet materials with non‐layered structures. [ABSTRACT FROM AUTHOR]

To boost the performance for various applications, a rational bottom‐up design on materials is necessary. The defect engineering on nanoparticle at the atomic level can efficiently tune the electronic behavior, which offers great opportunities in enhancing the catalytic performance. In this paper, we optimized the surface oxygen vacancy concentration and created the lattice distortion in rare‐earth‐based perovskite oxide through gradient replacement of the B site with valence alternated element. The dual defects make the electron spin state transit from low spin state to high spin state, thus decreasing the charge transport resistance. Furthermore, assembly the modified nanoparticle subunits into the micro‐sized hollow multishelled structures can provide porous shells, abundant interior space and effective contact, which enables an enhanced mass transfer and a shorter charge transport path. As a result, the systemic design in the electronic and nano‐micro structures for catalyst has brought an excellent oxygen evolution performance. [ABSTRACT FROM AUTHOR]

Surface lattice oxygen in transition‐metal oxides plays a vital role in catalytic processes. Mastering activation of surface lattice oxygen and identifying the activation mechanism are crucial for the development and design of advanced catalysts. A strategy is now developed to create a spinel Co3O4 /perovskite La0.3Sr0.7CoO3 interface by in situ reconstruction of the surface Sr enrichment region in perovskite LSC to activate surface lattice oxygen. XAS and XPS confirm that the regulated chemical interface optimizes the hybridized orbital between Co 3d and O 2p and triggers more electrons in oxygen site of LSC transferred into lattice of Co3O4 , leading to more inactive O2− transformed into active O2−x. Furthermore, the activated Co3O4/LSC exhibits the best catalytic activities for CO oxidation, oxygen evolution, and oxygen reduction. This work would provide a fundamental understanding to explain the activation mechanism of surface oxygen sites. [ABSTRACT FROM AUTHOR]

Exfoliation of non‐layered (structurally) bulk materials at the nanoscale is challenging because of the strong chemical bonds in the lattice, as opposed to the weak van der Waals (vdW) interactions in layered materials. We propose a top‐down method to exfoliate ϵ‐MnO2 nanosheets in a family of charge‐ordered La1−xAExMnO3 (AE=Ca, Sr, Ba) perovskites, taking advantage of the Jahn–Teller disproportionation effect of Mn3+ and bond‐strength differences. ϵ‐MnO2 crystallized into a nickel arsenide (NiAs) structure, with a thickness of 0.91 nm, displays thermal metastability and superior water oxidation activity compared to other manganese oxides. The exfoliation mechanism involves a synergistic proton‐induced Mn3+ disproportionation and structural reconstruction. The synthetic method could also be potentially extended to the exfoliation of other two‐dimensional nanosheet materials with non‐layered structures. [ABSTRACT FROM AUTHOR]

Surface lattice oxygen in transition‐metal oxides plays a vital role in catalytic processes. Mastering activation of surface lattice oxygen and identifying the activation mechanism are crucial for the development and design of advanced catalysts. A strategy is now developed to create a spinel Co3O4 /perovskite La0.3Sr0.7CoO3 interface by in situ reconstruction of the surface Sr enrichment region in perovskite LSC to activate surface lattice oxygen. XAS and XPS confirm that the regulated chemical interface optimizes the hybridized orbital between Co 3d and O 2p and triggers more electrons in oxygen site of LSC transferred into lattice of Co3O4 , leading to more inactive O2− transformed into active O2−x. Furthermore, the activated Co3O4/LSC exhibits the best catalytic activities for CO oxidation, oxygen evolution, and oxygen reduction. This work would provide a fundamental understanding to explain the activation mechanism of surface oxygen sites. [ABSTRACT FROM AUTHOR]