As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O2 reduction preferentially takes place on FeIII in the FeN4 /C system with intermediate spin state which possesses one eg electron (t2g4eg1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the FeIII sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO4), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm−2 and long-term durability in reversible zinc–air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.

Functionalized carbon nanomaterials, as significant options for renewable energy systems, are widely utilized in diversified electrochemical reactions in virtue of property advantages. The inevitable defect sites in architectures greatly affect physicochemical properties of carbon nanomaterials, thus defect engineering has recently become a vital research orientation of carbon‐based electrocatalysts. The intentionally introduced intrinsic carbon defect sites in the frameworks can directly serve as the potential active sites owing to the altered surface charge state, modulated adsorption free energy of key intermediates, as well as diminished bandgap. Furthermore, the synergistic sites between intrinsic defects and heteroatom dopants/captured atomic metal species can further optimize the electronic structure and adsorption/desorption behavior, making carbon‐based catalysts comparable to commercial precious metal catalysts in electrocatalysis. With pressing research demands, the common configurations, construction strategies, structure–activity relationships, and characterization methods for intrinsic carbon defect‐involved catalytic centers are systematically summarized. Such theoretical and experimental evidences of intrinsic defect‐induced activity can reveal the active centers and relevant catalytic mechanism, thereby providing necessary guidance for the design and construction of highly efficient carbon‐based electrocatalysts and promoting their commercial applications.

To overcome the current limitations of chemodynamic therapy (CDT), a Mo2C‐derived polyoxometalate (POM) is readily synthesized as a new CDT agent. It permits synergistic chemodynamic and photothermal therapy operating in the second near‐infrared (NIR‐II) biological transparent window for deep tissue penetration. POM aggregated in an acidic tumor micro‐environment (TME) whereby enables specific tumor targeting. In addition to the strong ability to produce singlet oxygen (1O2) presumably via Russell mechanism, its excellent photothermal conversion enhances the CDT effect, offers additional tumor ablation modality, and permits NIR‐II photoacoustic imaging. Benefitting from the reversible redox property of molybdenum, the theranostics based on POM can escape from the antioxidant defense system. Moreover, combining the specific responsiveness to TME and localized laser irradiation, side‐effects shall be largely avoided.

Theoretical calculations reveal that intrinsic pentagons in the basal plane can contribute to the local electronic redistribution and the contraction of band gap, making the carbon matrix possess superior binding affinity and electrochemical reactivity. To experimentally verify this, a pentagon‐defect‐rich carbon nanomaterial was constructed by means of in situ etching of fullerene molecules (C60). The electrochemical tests show that, relative to hexagons, such a carbon‐based material with abundant intrinsic pentagon defects makes much greater contribution to the electrocatalytic oxygen reduction activity and electric double layer capacitance. It shows a four‐electron‐reaction mechanism similar to commercial Pt/C and other transition‐metal‐based catalysts, and a higher specific capacitance than many reported metal‐free carbon materials. These results show the influence of intrinsic pentagon defects for developing carbon‐based nanomaterials toward energy conversion and storage devices.