Polymers are important precursors for the fabrication of carbon materials. Herein, halogenated polymers are explored as precursors for the synthesis of high-quality carbon materials via alkaline dehalogenation. It is found that the halogen elements (F, Cl) connecting to vinylidene units are highly reactive so that dehalogenation can take place a few seconds at room temperature by simple hand grinding in the presence of strong inorganic alkaline. Furthermore, the halogen element-leaving sites are shown to be susceptible to heteroatom doping (e.g., N doping) to become stable capacitive sites for charge storage (e.g., ions). By using a mixture of NaOEt and KOH as dehalogenation reagents, abundant hierarchical pores (macro/meso/micropores) in the resultant doped carbon matrix for fast mass transportation can be created. Very high capacitance (328 F g⁻¹ at 0.5 A g⁻¹) and rate capability (75.3% retention at 50 A g⁻¹ and 62.5% retention at 100 A g⁻¹) are observed for the newly developed halogenated polymer-derived doped carbon materials.

Investigations on Ag nanostructures/reduced graphene oxide composites have been frequently reported, yet the morphology control of those loaded Ag nanocrystals is still challenging. We herein develop a facile method to grow triangular Ag nanoplates (AgP) on polyethylenimine-modified reduced graphene oxide (AgP/PEI-rGO). The AgP/PEI-rGO hybrids show unexpected high stability against chloride ions (Cl⁻) and hydrogen peroxide (H₂O₂), which is possibly due to the strong interaction between surface Ag atoms with the amine groups of PEI. In the chronoamperometry measurements for detecting H₂O₂, N₂H₄, and NaNO₂, the AgP/PEI-rGO hybrid shows very wide linear ranges (usually 10⁻⁶–10⁻² mol L⁻¹ for H₂O₂, N₂H₄, and NaNO₂) and low detection limits (down to ≈1×10⁻⁷ mol L⁻¹), which demonstrate the promising electrochemical sensor applications of these metal/graphene hybrids with well-defined morphologies and facets. In addition, this strategy could be extended to the deposition of other noble metals on rGO with controlled morphologies.

Simultaneously synthesizing and structuring atomically thick or ultrathin 2D non-precious metal nanocrystal may offer a new class of materials to replace the state-of-art noble-metal electrocatalysts; however, the synthetic strategy is the bottleneck which should be urgently solved. Here we report the synthesis of an ultrathin nickel nanosheet array (Ni-NSA) through in situ topotactic reduction from Ni(OH)₂ array precursors. The Ni nanosheets showed a single-crystalline lamellar structure with only ten atomic layers in thickness and an exposed (111) facet. Combined with a superaerophobic (low bubble adhesive) arrayed structure the Ni-NSAs exhibited a dramatic enhancement on both activity and stability towards the hydrazine-oxidation reaction (HzOR) relative to platinum. Furthermore, the partial oxidization of Ni-NSAs in ambient atmosphere resulted in effective water-splitting electrocatalysts for the hydrogen-evolution reaction (HER).

Simultaneously synthesizing and structuring atomically thick or ultrathin 2D non-precious metal nanocrystal may offer a new class of materials to replace the state-of-art noble-metal electrocatalysts; however, the synthetic strategy is the bottleneck which should be urgently solved. Here we report the synthesis of an ultrathin nickel nanosheet array (Ni-NSA) through in situ topotactic reduction from Ni(OH)₂ array precursors. The Ni nanosheets showed a single-crystalline lamellar structure with only ten atomic layers in thickness and an exposed (111) facet. Combined with a superaerophobic (low bubble adhesive) arrayed structure the Ni-NSAs exhibited a dramatic enhancement on both activity and stability towards the hydrazine-oxidation reaction (HzOR) relative to platinum. Furthermore, the partial oxidization of Ni-NSAs in ambient atmosphere resulted in effective water-splitting electrocatalysts for the hydrogen-evolution reaction (HER).

Layered double hydroxides (LDHs) are a family of high-profile layer materials with tunable metal species and interlayer spacing, and herein the LDHs are first investigated as bifunctional electrocatalysts. It is found that trinary LDH containing nickel, cobalt, and iron (NiCoFe-LDH) shows a reasonable bifunctional performance, while exploiting a preoxidation treatment can significantly enhance both oxygen reduction reaction and oxygen evolution reaction activity. This phenomenon is attributed to the partial conversion of Co²⁺ to Co³⁺ state in the preoxidation step, which stimulates the charge transfer to the catalyst surface. The practical application of the optimized material is demonstrated with a small potential hysteresis (800 mV for a reversible current density of 20 mA cm⁻²) as well as a high stability, exceeding the performances of noble metal catalysts (commercial Pt/C and Ir/C). The combination of the electrochemical metrics and the facile and cost-effective synthesis endows the trinary LDH as a promising bifunctional catalyst for a variety of applications, such as next-generation regenerative fuel cells or metal–air batteries.

A pine-shaped Pt nanostructured electrode with under-water superaerophobicity for ultrahigh and steady hydrogen evolution reaction (HER) performance is successfully fabricated by a facile and easily scalable electrodeposition technique. Due to the lower bubble adhesive force (11.5 ± 1.2 μN), the higher bubble contact angle (161.3° ± 3.4°) in aqueous solution, and the smaller size of bubbles release for pine-shaped Pt nanostructured electrode, the incomparable under-water superaerophobicity for final repellence of bubbles from submerged surface with ease, is successfully achieved, compared to that for nanosphere electrode and for Pt flat electrode. With the merits of superior under-water superaerophobicity and excellent nanoarray morphology, pine-shaped Pt nanostructured electrode with the ultrahigh electrocatalytic HER performance, excellent durability, no obvious current fluctuation, and dramatically fast current density increase at overpotential range (3.85 mA mV⁻¹, 2.55 and 13.75 times higher than that for nanosphere electrode and for Pt flat electrode, respectively), is obtained, much superior to Pt nanosphere and flat electrodes. The successful introduction of under-water superaerophobicity to in-time repel as-formed H₂ bubbles may open up a new pathway for designing more efficient electrocatalysts with potentially practical utilization in the near future.

The oxygen evolution reaction (OER) is a critical step in water splitting to produce hydrogen. In this report, Au/NiCo₂O₄ nanorod arrays with high activity for OER have been fabricated by a facile hydrothermal method followed by a reduction process. The Au/NiCo₂O₄ nanoarrays exhibited OER activity that was almost four times higher than that of Ir/C (at 1.75 V vs. RHE), and a small Tafel slope (63 mV decade⁻¹). Moreover, this Au/NiCo₂O₄ hybrid-array electrode showed good stability in alkaline solution, which is required of an active anode for water electrolysis.

A simple and versatile synthesis method was developed to prepare inorganic multi-metal oxide hollow spheres with tunable compositions. The colloidal nanosheets of layered double hydroxides (LDH) with pre-determined compositions were used as precursors for multi-metal oxides and carbon spheres (CSs) prepared by hydrothermal carbonization of glucose were used as hard templates. Electrostatic force drove the positively charged LDH nanosheets to be anchored by the negatively charged CSs once they were mixed, leading to the formation of core-shell structures. Finally, multi-metal oxides with hollow spherical structures were obtained by calcination. These hollow spheres were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and inductively coupled plasma (ICP). Results revealed that the as-prepared oxide hollow spheres could exactly inherit the metal-to-metal ratios of initial LDH precursors, which provided an effective way to control the compositions of oxide shells. This strategy was suitable for preparation of a series of oxide hollow spheres from binary to multi-component ones, including MgO/Al₂O₃, MgO/Fe₃O₄, NiO/Al₂O₃, and ZnO/NiO/Al₂O₃.