Hard carbons with low cost and high specific capacity hold great potential as anode materials for potassium‐based energy storage. However, their sluggish reaction kinetics and inevitable volume expansion degrade their electrochemical performance. Through rational nanostructure design and a heteroatom doping strategy, herein, the synthesis of phosphorus/oxygen dual‐doped porous carbon spheres is reported, which possess expanded interlayer distances, abundant redox active sites, and oxygen‐rich defects. The as‐developed battery‐type anode material shows high discharge capacity (401 mAh g−1 at 0.1 A g−1), outstanding rate capability, and ultralong cycling stability (89.8% after 10 000 cycles). In situ Raman spectroscopy and density functional theory calculations further confirm that the formation of PC and PO/POH bonds not only improves structural stability, but also contributes to a rapid surface‐controlled potassium adsorption process. As a proof of concept, a potassium‐ion hybrid capacitor is assembled by a dual‐doped porous carbon sphere anode and an activated carbon cathode. It shows superior electrochemical performance, which opens a new avenue to innovative potassium‐based energy storage technology.

High current density hydrogen evolution reaction (HER) in alkaline water electrolysis plays crucial role in renewable and sustainable energy systems, while posing a great challenge to the highly‐efficient electrocatalysts. Here, the synthesis of Ni/NiO@MoO3−x composite nanoarrays is reported by a moderate reduction strategy, combining Ni/NiO nanoparticles (≈20 nm) with amorphous MoO3−x nanoarrays. The Ni/NiO@MoO3−x composite nanoarrays possess enhanced hydrophilicity, optimize reaction energy barriers, accelerate reactant diffusion/bubble detachment, and therefore display an ultrahigh alkaline HER activity with a low η10 overpotential of 7 mV as well as Tafel slope of 34 mV dec−1. More significantly, the Ni/NiO@MoO3−x nanoarrays only demand low overpotentials of 75 and 112 mV to deliver 100 and 200 mA cm−2 hydrogen production current, and can steadily work at 100 mA cm−2 for 40 h, which is more efficient and stable than the Pt/C catalyst.

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