Rational design of non‐noble metal catalysts with robust and durable electrocatalytic activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is extremely important for renewable energy conversion and storage, regenerative fuel cells, rechargeable metal–air batteries, water splitting etc. In this work, a unique hybrid material consisting of Fe3C and Co nanoparticles encapsulated in a nanoporous hierarchical structure of N‐doped carbon (Fe3C‐Co/NC) is fabricated for the first time via a facile template‐removal method. Such an ingenious structure shows great features: the marriage of 1D carbon nanotubes and 2D carbon nanosheets, abundant active sites resulting from various active species of Fe3C, Co, and NC, mesoporous carbon structure, and intimate integration among Fe3C, Co, and NC. As a multifunctional electrocatalyst, the Fe3C‐Co/NC hybrid exhibits excellent performance for ORR, OER, and HER, outperforming most of reported triple functional electrocatalysts. This study provides a new perspective to construct multifunctional catalysts with well‐designed structure and superior performance for clean energy conversion technologies.

Potassium‐ion batteries (PIBs) are considered as promising candidates for lithium‐ion batteries due to the abundant reserve and lower cost of K resources. However, K+ exhibits a larger radius than that of Li+, which may impede the intercalation of K+ into the electrode, thus resulting in poor cycling stability of PIBs. Here, an N/O dual‐doped hard carbon (NOHC) is constructed by carbonizing the renewable piths of sorghum stalks. As a PIB anode, NOHC presents a high reversible capacity (304.6 mAh g−1 at 0.1 A g−1 after 100 cycles) and superior cycling stability (189.5 mAh g−1 at 1 A g−1 after 5000 cycles). The impressive electrochemical performances can be ascribed to the super‐stable porous structure, expanded interlayer space, and N/O dual‐doping. More importantly, the NOHC can be prepared in large scale in a concise way, showing great potential for commercialization applications. This work may impel the development of low‐cost and sustainable carbon‐based materials for PIBs and other advanced energy storage devices.

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Li-substitution can improve the structural stability by forming an intermediate O′3 phase that can ease the destructive O3–P3 direct phase transition.

The size effects on Raman red shifts in low-dimensional semiconductor nanocrystals are investigated by considering the size-dependent root-mean-square average amplitude associated with the thermal vibration of atoms. The lower limit of vibrational frequency was obtained by matching the calculation results of Raman red shifts with the experimental data of Si, InP, CdSe, CdS0.65Se0.35, ZnO, CeO2, as well as SnO2 nanocrystals. The results indicate the following: (1) the Raman frequency decreases as the nanocrystal size decreases in both narrow and wide bandgap semiconductors; (2) the influence of crystal size on the Raman frequency of nanoparticles is more pronounced than that of nanowires and thin films; and (3) the Raman red shift is ascribed to the size-induced phonon confinement effect and surface relaxation. This model may provide new insights into the fundamental understanding of the underlying mechanism behind the Raman red shifts.