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The rational design and exploration of the oxygen evolution reaction (OER) electrocatalysts with high efficiency, low cost, and long-term durability are extremely important for overall water splitting. Recently, numerous studies have shown that the OER reaction kinetics can be modified by optimizing components, introducing carbon matrix, and regulating porous nanostructures. Herein, a flexible and controllable electrospinning strategy is proposed to construct porous nitrogen (N)-doped carbon (C) nanofibers (NFs) with nickel−iron (NiFe) alloy nanoparticles encapsulated inside (NiFe@NCNFs) as an OER electrocatalyst. Benefiting from the strong synergistic effects that stem from the one-dimensional mesoporous structures with optimized binary metal components encapsulated in the N-doped carbon nanofibers, the NiFe@NCNFs exhibits enhanced OER performance with a low overpotential (294 mV at 10 mA cm −2 ) and excellent durability (over 10 h at 10 mA cm −2 ) in alkaline solution. Both experimental characterizations and density functional theory (DFT) calculations validate that a suitable binary metal ratio can lead to the optimal catalytic activity. Moreover, a two-electrode electrolyzer is assembled by using NiFe@NCNFs anode and Pt/C cathode in 1.0 M KOH media for the overall water splitting, which delivers an initial cell voltage of only 1.531 V at 10 mA cm −2 , as well as long-term stability up to 20 h. This study sheds light on the design and large-scale production of low-cost and high-performance electrocatalysts toward different energy applications in the future.

Layer-structured vanadium oxide (V 2 O 5 ) nanoribbons with efficient electron transport and short lithium ion insertion lengths are promising candidates for high-performance lithium-ion battery applications. Despite the extensive investigation of its electrochemical properties, the chemical and structural evolution during lithiation−delithiation processes has rarely been characterized in real time. Herein, the lithiation−delithiation behaviors of V 2 O 5 nanoribbons are probed by in situ transmission electron microscopy. We reveal that the V 2 O 5 nanoribbons exhibit high lithiation speed (0.8 nm/s) without retardation along the [010] direction and can be fully lithiated to the Li 3 V 2 O 5 phase. Fully reversible retraction of lithium is observed in these V 2 O 5 nanoribbons during delithiation. The lithiation process accompanying the coherent strain is further simulated by our phase field model. The simulation results reveal that the specific rough lithiation interface between the V 2 O 5 and Li 3 V 2 O 5 phases originates from the lithiation inhomogeneity.

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