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Atomically dispersed iron–nitrogen–carbon catalysts are promised, low‐cost, and high‐performance electrocatalysts for the Oxygen Reduction Reaction (ORR) in fuel cells. However, most Fe–N–C materials are produced via pyrolysis at a high temperature and it is difficult to characterise the precise Fe–N configurations. This can lead to confusion surrounding the best chemical and coordination environment for Fe and understanding the subsequent ORR mechanisms. In this work, Fe porphyrin is used to produce a specific Fe–N environment, therefore allowing the role and activity of this environment to be studied. Carbon nanotubes (CNTs) are covalently functionalized with iron 5,10,15,20‐triphenylporphyrin (FeTPP) motifs via aryl diazonium methodology, enabling the exact role of only the Fe‐Pyrrolic N4 configuration of FeTPP in ORR to be studied and better understood. Upon covalent functionalization, a high electrochemical active site density of 1.12 × 1015 sites cm−2, approximately six‐fold more than that of noncovalently functionalized samples with 12.7% electrochemical active site. The heightened active site density and superior electrochemical active site utilization (12.7%) lead to the more favorable 4‐electron pathway for the ORR. Furthermore, a preliminary discussion regarding the selectivity of the ORR pathway is initiated. [ABSTRACT FROM AUTHOR]

Thermal evaporation can significantly facilitate scalable, uniform, and conformal perovskite film, particularly well‐suited for the preparation of perovskite/silicon (Si) tandem solar cells. However, the perovskite material easily induces a phase transition from a photoactive phase to a photoinactive phase, limiting the development of the stability and efficiency of tandem cells. Introducing lead chloride (PbCl2) into wide‐bandgap perovskite materials is beneficial for the fabrication of efficient and stable light‐absorbing materials, but the microscopic mechanism of the effect of PbCl2 on perovskite is still unclear. The study here reports evidences that the addition of PbCl2 to improve perovskite film stability and optoelectronic performance is due to the minor octahedral tilting of the perovskite structure are reported. It also demonstrates that this strategy accelerates interfacial charge transfer and carrier diffusion in the perovskite bulk and heterojunction interfaces. Therefore, the wide‐bandgap perovskite solar cells (PSCs) prepared by adding PbCl2 exhibit a champion power conversion efficiency (PCE) of 17.80%. The PSCs retain 97% of their performance following 200 h of operation at the maximum power point under full 1‐sun illumination. Finally, monolithic perovskite/Si tandem cells with record PCEs of 27.43% and an open‐circuit voltage of 1.817 V are fabricated. [ABSTRACT FROM AUTHOR]

Rapidly increasing demand for energy density in consumer electronics is eager for developing high‐voltage LiCoO2 (LCO). However, some great challenges such as severe phase transition and surface instability negate the cycle life of LCO operated at high‐voltages (≥4.6 V). Herein, a chemical reconstruction strategy is proposed to form a collective surface of LCO through an interdiffusion reaction of MgHPO4·3H2O (MP) so as to extend the cycle life of high‐voltage LCO. The collective surface renders a three‐layer configuration that demonstrates an amorphous Li3PO4 outmost layer, a spinel‐like layer beneath, and a Mg diffusion layer within LCO bulk. MP with relatively low hardness enables the uniform precoating via mechanical mixing, followed by a sintering process to undergo an interdiffusion reaction. Li3PO4 is an intrinsic electrochemical stabilizer against interfacial side reactions. The spinel‐like compounds build a high‐voltage‐stable surface against irreversible O2 release. In addition, Mg diffuses into the bulk lattice to suppress irreversible phase transition during the deep delithiation of LCO. Therefore, such modified LCO with a collective surface exhibits ultralong life with capacity retention of 82% after 1000 cycles at 1 C within 3.0–4.6 V and stable operating at 4.7 V or elevated temperature (45 °C). [ABSTRACT FROM AUTHOR]

Biofilms are the chief culprits of most intractable infections and pose great threat to human health. Developing effective strategies to sweep away the detrimental microbe and stubborn biofilm still remains a challenge. Here, an ultrasound (US) activated microbomb is constructed by encapsulating perfluorohexane (PFH) and iron‐tannin modified calcium peroxide (CaO2‐TA‐Fe) in poly(lactide‐co‐glycolide) (PLGA) vesicles as the reactive oxygen species (ROS) generating reactors for dental biofilm elimination. Upon the US irradiation by ultrasonic toothbrush, the swiftly vaporized PFH can not only promptly explode the PLGA shell to facilitate the generation of H2O2 from CaO2, but also blast the tight biofilm for effective delivery of the lethal hydroxyl free radicals (•OH) caused by degradative Fe3+ from iron‐tannin network, thereby proceeding cascade catalysis eradication of biofilm. As a proof‐of‐concept, this study demonstrates the proposed synergetic paradigm that integrates the US‐triggered explosion with ROS‐induced sterilization for stubborn biofilm elimination, and is a promising tactic for the costly and prevalent caries prevention as well as the biofilm‐associated diseases treatments. [ABSTRACT FROM AUTHOR]

Li‐rich Mn‐based layered oxides (LRLOs) with ultrahigh specific capacities are promising cathode materials for high energy density lithium‐ion batteries. Nevertheless, severe irreversible oxygen release, structure degradation, capacity and voltage attenuation hinder their commercialization due to the uncontrollable oxygen redox chemistry originated from unhybridized O 2p orbitals. Herein, a strategy to generate bulk oxygen vacancies is proposed. And bulk oxygen vacancies are constructed by lowering the formation energy of oxygen vacancies in LRLOs via Gd‐doping. The energy level and the amount of unhybridized O 2p states are reduced to partly inhibit the oxygen redox activity. Surprisingly, the oxygen redox is not fully activated in the first cycle and is further activated in the second cycle. Moreover, the reduced oxygen redox activity significantly suppresses the oxygen release, lattice volume change, layered‐to‐spinel phase transition. As a result, the amount of oxygen gas release is reduced from 98.80 to ≈0 nmol mg−1 in the first cycle. Superior cycle stability of 90.4% capacity retention after 300 cycles and small voltage decay of only 1.013 mV per cycle are achieved. This study provides a valuable bulk oxygen vacancies strategy to regulate the unhybridized O 2p orbitals for designing high‐performance Li‐rich Mn‐based layered oxide cathode materials. [ABSTRACT FROM AUTHOR]

In most electrochemical energy storage and conversion devices, nanostructured carbon materials play essential roles. One-step carbonization of some biomass materials has recently been demonstrated as a promising route to produce high surface area carbon without introducing extra activation agents. Here, this study shows the importance of physiologic function of plant organs in the microstructure and porosity of formed carbon nanomaterials. The lotus stem pyrolyzed carbon at 800 °C presents a specific surface area of 1610 m2 g−1, about 55% higher than the porous carbon from the leaves. A similar organ-dependent effect in the porosity of the pyrolyzed carbon is also observed in other plants with wide disparity in the stems and leaves, such as celery and asparagus lettuce, largely due to the higher metal ion content in the stems, which plays the role of ion transportation for plants. Furthermore, optimizing the celery stem pyrolyzing condition can produce carbon with specific surface area as high as 2194 m2 g−1 without any extra activation process. As a supercapacitor electrode, the porous carbon pyrolyzed from lotus stems exhibits a specific capacitance of 174 F g−1 at a scan rate of 5 mV s−1 in 6 M KOH aqueous electrolyte, with 72% capacitance retention at a high scan rate of 500 mV s−1 and good stability over 10 000 cycles. [ABSTRACT FROM AUTHOR]