Herein, we demonstrate the synthesis of bifunctional nickel cobalt selenide@nickel telluride (Ni_xCo_12-xSe@NiTe) core–shell heterostructures via an electrodeposition approach for overall urea electrolysis and supercapacitors. The 3D vertically orientated NiTe dendritic frameworks induce the homogeneous nucleation of 2D Ni_xCo_12-xSe nanosheet arrays along similar crystal directions and bring a strong interfacial binding between the integrated active components. In particular, the optimized Ni₆Co₆Se@NiTe with an interface coupling effect works in concert to tune the intrinsic activity. It only needs a low overpotential of 1.33 V to yield a current density of 10 mA cm⁻² for alkaline urea electrolysis. Meanwhile, the full urea catalysis driven only by Ni₆Co₆Se@NiTe achieves 10 mA cm⁻² at a potential of 1.38 V and can approach a constant level of the current response for 40 h. Besides, the integrated Ni₆Co₆Se@NiTe electrode delivers an enhanced specific capacity (223 mA h g⁻¹ at 1 A g⁻¹) with a high cycling stability. Consequently, a hybrid asymmetric supercapacitor (HASC) device based on Ni₆Co₆Se@NiTe exhibits a favorable rate capability and reaches a high energy density of 67.7 Wh kg⁻¹ and a power density of 724.8 W kg⁻¹ with an exceptional capacity retention of 92.4% after sequential 12 000 cycles at 5 A g⁻¹.

Approximately 15 nm thick nitrogen-doped lanthanum titanate (La₂Ti₂O₇) nanosheets with a single-crystalline perovskite structure have been prepared by hydrothermal processing and subsequent heat treatment in NH₃ at 600 ℃. Doping nitrogen into the La₂Ti₂O₇ nanosheets results in the narrowing of the band gap, extending the light absorption into the visible light region (~495 nm). The nitrogen-doped La₂Ti₂O₇ nanosheets not only show significant visible light photocatalytic activity toward the decomposition of methyl orange but also exhibit enhanced the ultraviolet light photocatalytic activity. The enhancement of photocatalytic activity originates from the narrowing of the band gap of La₂Ti₂O₇ nanosheets. The results obtained show that the desirable route to extend the photocatalytic activity of a semiconductor from the ultraviolet to the visible light region is to narrow the band gap rather than to create localized mid-gap states.