Tuning the Electrocatalytic Activity of Co3O4 through Discrete Elemental Doping

Bifunctional Square-Planar NiO4 Coordination of Topotactic LaNiO2.0 Films for Efficient Oxygen Evolution Reaction

The high-efficient and low-cost oxygen evolution reaction (OER) is decisive for applications of oxide catalysts in metal-air batteries, electrolytic cells, and energy-storage technologies. Delicate regulations of active surface and catalytic reaction pathway of oxide materials principally determine thermodynamic energy barrier and kinetic rate during catalytic reactions, and thus have crucial impacts on OER performance. Herein, a synergistic modulation of catalytically active surface and reaction pathway through facile topotactic transformations switching from perovskite (PV) LaNiO3.0 film to infinite-layer (IL) LaNiO2.0 film is demonstrated, which absolutely contributes to improving OER performance. The square-planar NiO4 coordination of IL-LaNiO2.0 brings about more electrochemically active metal (Ni+ ) sites on the film surface. Meanwhile, the oxygen-deficient driven PV- IL topotactic transformations lead to a reaction pathway converted from absorbate evolution mechanism to lattice-oxygen-mediated mechanism (LOM). The non-concerted proton-electron transfer of LOM pathway, evidenced by the pH-dependent OER kinetics, further boosts the OER activity of IL-LaNiO2.0 films. These findings will advance the in-depth understanding of catalytic mechanisms and open new possibilities for developing highly active perovskite-derived oxide catalysts.

Lewis Acid Site Assisted Bifunctional Activity of Tin Doped Gallium Oxide and Its Application in Rechargeable Zn-Air Batteries

The enhanced safety, superior energy, and power density of rechargeable metal-air batteries make them ideal energy storage systems for application in energy grids and electric vehicles. However, the absence of a cost-effective and stable bifunctional catalyst that can replace expensive platinum (Pt)-based catalyst to promote oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air cathode hinders their broader adaptation. Here, it is demonstrated that Tin (Sn) doped β-gallium oxide (β-Ga₂ O₃ ) in the bulk form can efficiently catalyze ORR and OER and, hence, be applied as the cathode in Zn-air batteries. The Sn-doped β-Ga₂ O₃ sample with 15% Sn (Sn_{x =0.15} -Ga₂ O₃ ) displayed exceptional catalytic activity for a bulk, non-noble metal-based catalyst. When used as a cathode, the excellent electrocatalytic bifunctional activity of Sn_{x =0.15} -Ga₂ O₃ leads to a prototype Zn-air battery with a high-power density of 138 mW cm^-2 and improved cycling stability compared to devices with benchmark Pt-based cathode. The combined experimental and theoretical exploration revealed that the Lewis acid sites in β-Ga₂ O₃ aid in regulating the electron density distribution on the Sn-doped sites, optimize the adsorption energies of reaction intermediates, and facilitate the formation of critical reaction intermediate (O*), leading to enhanced electrocatalytic activity.

Hollow POM@MOF-derived Porous NiMo6 @Co3 O4 for Biothiol Colorimetric Detection

Developing highly active and sensitive peroxidase mimics for _L -cysteine (_L -Cys) colorimetric detection is very important for biotechnology and medical diagnosis. Herein, polyoxometalate-doped porous Co₃ O₄ composite (NiMo₆ @Co₃ O₄ ) was designed and prepared for the first time. Compared with pure and commercial Co₃ O₄ , NiMo₆ @Co₃ O₄ (n) composites exhibit the enhanced peroxidase-mimicking activities and stabilities due to the strong synergistic effect between porous Co₃ O₄ and multi-electron NiMo₆ clusters. Moreover, the peroxidase-mimicking activities of NiMo₆ @Co₃ O₄ (n) composites are heavily dependent on the doping mass of NiMo₆ , and the optimized NiMo₆ @Co₃ O₄ (2) exhibits the superlative peroxidase-mimicking activity. More importantly, a sensitive _L -Cys colorimetric detection is developed with the sensitivity of 0.023 μM^-1 and the detection limit at least 0.018 μM in the linear range of 1-20 μM, which is by far the best enzyme-mimetic performances, to the best our knowledge.

Single-Atom Catalysts across the Periodic Table

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.