We provide strong evidence of the effectiveness of homogenously self-propelled particle-in-particle diffusion, interaction and growth protocol. This technique was used for one-pot synthesis of novel nitrogen-graphene oxide (N-GO)/Co₃O₄ nanocrystals with cuboid rectangular prism-shaped nanorods (NRs) along {110}-plane and truncated polyhedrons with densely-exposed, multi-facet sites along {311} and {111} planes. These hierarchal nanocrystals create electrode catalyst patterns with vast-range accessibility to active Co²⁺ sites, a vascular system for the transport and retention of captured O₂ molecule interiorly, and low adsorption energy and dense electron configuration surfaces during the oxygen reduction reaction (ORR). The superior electrocatalytic ORR activity of the N-GO/Co₃O₄ polyhedron nanocrystals in terms of electrochemical selectivity, durability and stability compared with NRs or commercial Pt/C catalysts confirms the synergetic contribution of multi-functional, dense-exposed, and actively topographic facets of polyhedrons to significantly activate the catalytic nature of the catalyst. Our findings show real evidence, for the first time that not only the large number of catalytically active Co²⁺ cations at the top surface layer but also the dense location of active Co²⁺ sites on the upper-zone top-on-plane exposure, and the electron density configuration and distribution around the Co²⁺ sites were important for effective ORR.

Novel electrodes are needed for direct ethanol fuel cells with improved quality. Hierarchical engineering can produce catalysts composed of mesocrystals with many exposed active planes and multi-diffused voids. Here we report a simple, one-pot, hydrothermal method for fabricating Co₃O₄/carbon/substrate electrodes that provides control over the catalyst mesocrystal morphology (i.e., corn tubercle pellets or banana clusters oriented along nanotube domains, or layered lamina or multiple cantilevered sheets). These morphologies afforded catalysts with a high density of exposed active facets, a diverse range of mesopores in the cage interior, a window architecture and vertical alignment to the substrate, which improved efficiency in an ethanol electrooxidation reaction compared with a conventional platinum/carbon electrode. On the atomic scale, the longitudinally aligned architecture of the Co₃O₄mesocrystals resulted in exposed low- and high-index single and interface surfaces that had improved electron transport and diffusion compared with currently used electrodes.

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.