A cost-efficient and stable oxygen evolution electrocatalyst is essential for improving energy storage and conversion efficiencies. Herein, 2D nanosheets with randomly cross-linked CoNi layered double hydroxide (LDH) and small CoO nanocrystals were designed and synthesized via in situ reduction and interfacedirected assembly in air. The formation of CoNi LDH/CoO nanosheets was attributed to the strong extrusion of hydrated metal–oxide clusters driven by the interfacial tension. The obtained loose and porous nanosheets exhibited low crystallinity due to the presence of numerous defects. Owing to the orbital hybridization between metal 3d and O 2p orbitals, and electron transfer between metal atoms through Ni–O–Co, a number of Co and Ni atoms in the CoNi LDH present a high +3 valency. These unique characteristics result in a high density of oxygen evolution reaction (OER) active sites, improving the affinity between OH^– and catalyst, and resulting in a large accessible surface area and permeable channels for ion adsorption and transport. Therefore, the resulting nanosheets exhibited high catalytic activity towards the OER. The CoNi LDH/CoO featured a low onset potential of 1.48 V in alkaline medium, and required an overpotential of only 300 mV at a current density of 10 mA·cm^–2, while displaying good stability in accelerated durability tests.

A large-area, self-supported Co ₃ O ₄ nanocrystal/carbon fiber electrode for oxygen and hydrogen evolution reaction was fabricated via thermal decomposition of the [Co(NH ₃ ) _n ] ²⁺ –oleic acid complex and subsequent spray deposition.

Enzymeless hydrogen peroxide (H₂O₂) detection with high sensitivity and excellent selectivity is desirable for clinical diagnosis. Herein, one-dimensional Co₃O₄ nanowires have been successfully constructed on reduced graphene oxide (rGO) via a simple hydrothermal procedure and subsequent thermal treatment. These Co₃O₄ nanowires, assembled by small nanoparticles, are interlaced with one another and make a spider web-like structure on rGO. The formation of Co₃O₄-rGO hybrids is attributed to the structure-directing and anchoring roles of DDA and GO, respectively. The resulting structure possesses abundant active sites, the oriented transmission of electrons, and unimpeded pathways for matter diffusion, which endows the Co₃O₄-rGO hybrids with excellent electrocatalytic performance. As a result, the obtained Co₃O₄-rGO hybrids can serve as an efficient electrochemical catalyst for H₂O₂ oxidation and high sensitivity detection. Under physiological conditions, the oxidation current of H₂O₂ varies linearly with respect to its concentration from 0.015 to 0.675 mM with a sensitivity of 1.14 mA·mM⁻¹·cm⁻² and a low detection limit of 2.4 μM. Furthermore, the low potential (−0.19 V) and the good selectivity make Co₃O₄-rGO hybrids suitable for monitoring H₂O₂ generated by liver cancer HepG2 cells. Therefore, it is promising as a non-enzymatic sensor to achieve real-time quantitative detection of H₂O₂ in biological applications.

Although, as early as 2014, theoretical investigations have illuminated that nonmetallic heteroatom doped graphene (NHDG) is anticipated to achieve excellent catalytic activity approaching that of platinum for the hydrogen evolution reaction (HER), its actual HER performance, even today, is still worse than that of the transition metal-based catalysts used as benchmarks. The lack of an effective way capable of extensively and precisely modulating the allocation (e.g., the proportion, content and configuration) of heteroatoms in NHDG presents a substantial impediment. Herein, encouraged by our systematic theoretical result that optimizing the heteroatom allocation in graphene could significantly boost the HER performance, we regulate, for the first time, the proportion and content of heteroatoms in N, P codoped graphene (G-NP) accurately by a judiciously designed supramolecular architecture. The key to implementation lies in the well-built H-bonded supramolecular architecture (melamine–phosphoric acid)/graphene oxide assemblies, in which, during the pyrolysis, the architecture of melamine and phosphoric acid functions as not only a “spacer” to suppress the stacking of graphene nanosheets, but also a self-sacrificial dopant for extensively tuning the allocation of N and P in a wide range. The optimal G-NP can acquire a moderate hydrogen adsorption Gibbs free-energy, an enhanced conductivity and a large electrochemical surface area, and display an extremely low overpotential of 106 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ solution, ranking first in the reported NHDG catalysts and outperforming many state-of-the-art metallic catalysts. This work not only presents a cost-effective, efficient strategy to regulate the allocation of heteroatoms in doped graphene but also offers insight for better design and fabrication of advanced NHDG for different applications.