Suppressing the formation of defects such as oxygen vacancies and Ti3+ in SrTiO3 perovskite lattice has been regarded as an effective way to improve photocatalytic performance in overall water-splitting reaction. In this work, a series of La,Al-codoped SrTiO3 catalysts are synthesized by a flux treatment method after grounding. An appropriate doping amount of La3+ and Al3+ ions into perovskite will lead to fewer defects, responsible for enhancing photocatalytic performance. Al3+ ion doping will introduce the oxygen vacancies into the perovskite, resulting in a decreasing number of Ti3+ ions. During the defect engineering, more Sr2+ will precipitate onto the perovskite surface caused by the introduction of Al3+. Hence, surface engineering is applied through appropriate La3+ ion doping contributing to the lattice distortion, allowing surficial Sr2+ to re-enter the perovskite lattice, leading to the promoted conversion of Ti3+ to Ti4+. Simultaneously, the La3+ ion doping is also beneficial to the decrease in oxygen vacancies. As a result, the essential relationship between the La3+ doping amount and photocatalytic performance in overall water splitting is revealed. The optimized 0.6% La and 1% Al codoped SrTiO3 sample loading Rh (0.1 wt %)/Cr2O3 (0.05 wt %)/CoOOH (0.05 wt %) gives the highest activity and good stability, with gas evolution rates of 1.79 mmol·h–1 (H2) and 0.91 mmol·h–1 (O2). In comparison, the apparent quantum efficiency is 78.43% under 365 nm irradiation.

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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.

Decreasing the Ti 3+ defect concentration in SrTiO 3 is recognized as the focus of seeking a perfect photocatalytic activity. However, the defect-engineered SrTiO 3 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 SrTiO 3 to obtain a close low-level concentration of Ti 3+ defect for comparison. An interesting phenomenon is found that the K-doped SrTiO 3 has a higher Ti 3+ 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 SrTiO 3 , 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 Ti 3+ defect concentration in theory, for designing defect engineering in SrTiO 3 .