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Decreasing the Ti3+ defect concentration in SrTiO3 is recognized as the focus of seeking a perfect photocatalytic activity. However, the defect‐engineered SrTiO3 by doping different low‐valence metal ions have no similarly good activity in overall water spitting, of which the reason has not been determined. Here, Na+, K+, and Cs are deliberately doped in SrTiO3 to obtain a close low‐level concentration of Ti3+ defect for comparison. An interesting phenomenon is found that the K‐doped SrTiO3 has a higher Ti3+ concentration than others but with a better intrinsic photocatalytic activity. The analysis of band structure and charge‐carriers behavior indicates the formation of a deep‐state defect in Na or Cs‐doped SrTiO3, leading to a decrease in photocatalytic activity. With the density functional theory calculation and synchrotron radiation characterization, the differences in A‐site‐metal ionic polarization are found to localize some defect charge, accompanied by uneven structural relaxation. As a result, the deep‐state defect can form in the area containing some group of atoms around the higher‐polarization metal ions, limiting the activity. This study further complements the important effect of doping ions on defect state in addition to the Ti3+ defect concentration in theory, for designing defect engineering in SrTiO3. [ABSTRACT FROM AUTHOR]

MnO/C materials with a long lifetime and high rate performance via a biomass template strategy for the lithium ion battery (LIB) market are indispensable. Therefore, novel and efficient ways for their synthesis are urgently required to greatly alleviate the pressure of consuming nonrenewable resources. Herein, we fabricate an open hollow tubular MnO/C hybrid based on the transformation of a natural kapok fiber by hydrothermal and thermal treatment. The as-prepared hybrid material was obtained with high synthesis efficiency and exhibited an extremely stable structure attributed to the in situ growth strategy, overcoming volumetric expansion and self-aggregation of MnO. As an anode material for LIBs, this typical MnO/C electrode demonstrated a high reversible capacity of 1917 mAh · g -1 at 300 mA · g -1 and an excellent rate performance of 693.1 mAh · g -1 at 5000 mA · g -1 . More importantly, this biomass carbon-based material demonstrates a superior cycling stability of 1433.1 mAh · g -1 at a high current density of 5000 mA · g -1 after 1000 cycles. The significant electrical performance of this new type of green material is promising for the development of LIBs.