High-entropy multi-elemental (HEM) electrocatalysts present superior catalytic performance due to the efficient synergism of their components. HEM electrocatalysts are usually prepared through hydrothermal reactions or calcination, which could generate undesired heterogeneous structures that hinder the exploration of the structure–property relationship of these HEM electrocatalysts. Herein, we report a sol-gel method to synthesize homogeneous HEM electrocatalysts for electro-oxidation of methanol and urea (methanol oxidation reaction (MOR) and urea oxidation reaction (UOR)), through an acid-catalyzed gelation at room temperature. With Ni as the primary component for MOR and UOR, Co can reduce the overpotentials, while Fe can increase the catalytic activities and durability. Borate and phosphate can tune the charge distribution in active sites and speed up the reaction kinetics through fast proton transfer. Thus, the optimal Ni₂Fe_0.5Co_0.5-BP HEM catalyst demonstrates superior catalytic activity together with good durability and great resistance to CO poisoning. In addition, a direct methanol fuel cell with Ni₂Fe_0.5Co_0.5-BP electrode can not only provide power, but also produce formic acid with high yield and high Faraday efficiency. This work presents a simple strategy to prepare high-performance HEM electrocatalysts for fuel cells and production of value-added chemicals.

The continuous tuning of plasmonic nanoassembly’s structure is the key to manipulate their optical and catalytic properties. Herein, we report a strategy of using macroscopic deformation to continuously tune the structure and optical activity of massive plasmonic nanoassemblies that are embedded in elastic polymer matrix. Plasmonic gold nanoparticles (Au NPs) are assembled to nanochains (Au NCs) with defined length and further embedded into polyvinylpyrrolidone (PVP) matrix. The nanostructure and plasmonic properties of massive Au NCs in this Au NCs-PVP film can be simultaneously and continuously tuned, simply by reversible mechanical deformation of this elastic film. In this way, the surface-enhanced Raman scattering (SERS) enhancement factor of this film as a SERS substrate can be mechanically modulated in the range of 10⁰ to 6.8 ×10⁷. Meanwhile, the PVP matrix also serves as a selective diffusion barrier to eliminate the fluorescence interference of large biomolecules, which enables the Au NCs-PVP film as a convenient SERS substrate for quick and direct analysis of small molecule analytes in biological samples and food, avoiding the complicate and time-consuming sample pretreatment process.

The dimensional confinement endows ultrathin nanosheets with unique physical and chemical properties, which have been widely studied for the purpose of developing active electrocatalysts for water splitting. Ultrathin nanosheets are generally synthesized by chemical vapor deposition, exfoliation, or surfactant-assisted synthesis, which either require special equipment and reaction conditions, or is limited by the low yields and the difficulty in controlling the lateral size and structure of the nanosheets. In addition, achieving a high loading of ultrathin nanosheets on the electrodes without compromising their catalytic activity still remains a challenge. Herein, we report a simple electrodeposition method for preparing Co₃O₄ and Co(OH)₂ ultrathin nanosheet arrays (UNA) without using templates or surfactants. The obtained arrays exhibit high activity for oxygen and hydrogen evolution reactions, in both alkaline and neutral media. The electrolyzer based on Co₃O₄ and Co(OH)₂ UNA shows superior activity and stability than that based on IrO₂ and Pt/C, which demonstrates the potential of the present electrodeposition method for developing active and stable electrocatalysts for water splitting.