Metal‐organic frameworks (MOFs) are promising porous precursors for the construction of various functional materials for high‐performance electrochemical energy storage and conversion. Herein, a facile two‐step solution method to rational design of a novel electrode of hollow NiCo2O4 nanowall arrays on flexible carbon cloth substrate is reported. Uniform 2D cobalt‐based wall‐like MOFs are first synthesized via a solution reaction, and then the 2D solid nanowall arrays are converted into hollow and porous NiCo2O4 nanostructures through an ion‐exchange and etching process with an additional annealing treatment. The as‐obtained NiCo2O4 nanostructure arrays can provide rich reaction sites and short ion diffusion path. When evaluated as a flexible electrode material for supercapacitor, the as‐fabricated NiCo2O4 nanowall electrode shows remarkable electrochemical performance with excellent rate capability and long cycle life. In addition, the hollow NiCo2O4 nanowall electrode exhibits promising electrocatalytic activity for oxygen evolution reaction. This work provides an example of rational design of hollow nanostructured metal oxide arrays with high electrochemical performance and mechanical flexibility, holding great potential for future flexible multifunctional electronic devices.

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Artificial nitrogen fixation through the nitrogen reduction reaction (NRR) under ambient conditions is a potentially promising alternative to the traditional energy-intensive Haber–Bosch process. For this purpose, efficient catalysts are urgently required to activate and reduce nitrogen into ammonia. Herein, by the combination of experiments and first-principles calculations, we demonstrate that copper single atoms, attached in a porous nitrogen-doped carbon network, provide highly efficient NRR electrocatalysis, which compares favorably with those previously reported. Benefiting from the high density of exposed active sites and the high level of porosity, the Cu SAC exhibits high NH3 yield rate and Faradaic efficiency (FE), specifically ∼53.3 μgNH3 h–1 mgcat –1 and 13.8% under 0.1 M KOH, ∼49.3 μgNH3 h–1 mgcat –1 and 11.7% under 0.1 M HCl, making them truly pH-universal. They also show good stability with little current attenuation over 12 h of continuous operation. Cu–N2 coordination is identified as the efficient active sites for the NRR catalysis.

The Al effect on the electrochemical properties of layered double hydroxides (LDHs) is not properly probed, although it is demonstrated to notably promote the capacitive behavior of LDHs. Herein, ternary NiCo 2 Al x layered double hydroxides with varying levels of Al stoichiometry are purposely developed, grown directly on mechanically flexible and electrically conducting carbon cloth (CC@NiCo 2 Al x -LDH). Al plays a significant role in determining the structure, morphology, and electrochemical behavior of NiCo 2 Al x -LDHs. At an increasing level of Al in NiCo 2 Al x -LDHs, there is a steady evolution from 1D nanowire to 2D nanosheets. The CC@NiCo 2 Al-LDH at an appropriate level of Al and with the nanowire-nanosheet mixed morphology exhibits both significantly enhanced electrochemical performance and excellent structural stability, with about a 2.3-fold capacitance of NiCo 2 -OH. When applied as the anode in a flexible asymmetric supercapacitor (ASC), the CC@NiCo 2 Al-LDH gives rise to a remarkable energy density of 44 Wh kg −1 at the power density of 462 W kg −1 , together with remarkable cyclic stability with 91.2% capacitance retention over 15 000 charge-discharge cycles. The present study demonstrates a new pathway to significantly improve the electrochemical performance and stability of transition metal LDHs, which are otherwise unstable in structure and poorly performing in both rate and cycling capability.

Tubular CoS2 nanoarrays successfully aligned on carbon cloth were rationally designed and fabricated from a metal organic framework precursor, and can be utilized as an efficient bifunctional electrocatalyst for overall water splitting.