Natural enzymes are highly efficient catalysts with strong substrate specificity, making them ideal for biomedical applications. However, they often face issues such as variability, high costs, challenging preparation processes, and difficulties in large-scale production. This has led to significant efforts in developing effective nanoenzymes and exploring their application potential. In recent years, carbon dots (CDs) have gained attention due to their strong fluorescence, excellent biocompatibility, and low cytotoxicity. Cationic CDs, which possess a positively charged surface, have shown the ability to mimic natural enzyme applications. The positive charge on the surfaces of these nanomaterials significantly influences their fluorescence, biological activity, and interactions with other biomolecules. Therefore, understanding how surface charge affects the performance of CDs is crucial for enhancing their usability. Considerable progress has been made in the design, synthesis, and mechanistic research of enzyme-like cationic CDs, as well as their advanced applications. This article reviews the latest research on the design structure, catalytic mechanisms, biosensing capabilities, and biomedical applications of enzyme-like cationic CDs. First, we review the synthesis strategies for cationic CDs and how surface charge influences their physical and chemical properties. Next, we highlight various applications of these cationic CDs, demonstrating their use in areas such as detection, biomedical applications (including antibacterial agents, gene carriers, and therapeutic agents), catalysis, and more. Finally, we discuss the challenges and obstacles faced in the development of cationic CDs and look forward to exploring new applications in the future.

Electrocatalytic nitrate reduction reaction (NitRR) is an efficient route for simultaneous wastewater treatment and ammonia production, but the conversion of NO₃^– to NH₃ involves multiple electron and proton transfer processes and diverse by-products. Therefore, developing ammonia catalysts with superior catalytic activity and selectivity is an urgent task. The distinctive electronic structure of Cu enhances the adsorption of nitrogen-containing intermediates, but the insufficient activation capability of Cu for interfacial water restricts the generation of reactive hydrogen and inhibits the hydrogenation process. In this work, a Ce-doped CuO catalyst (Ce₁₀/CuO) was synthesized by in situ oxidative etching and annealing. The redox of Ce³⁺/Ce⁴⁺ enables the optimization of the electronic structure of the catalyst, and the presence of Ce³⁺ as a defect indicator introduces more oxygen vacancies. The results demonstrate that Ce₁₀/CuO provides an impressive ammonia yield of 3.88 ± 0.14 mmol·cm^–2·h^–1 at 0.4 V vs. reversible hydrogen electrode (RHE) with an increase of 1.04 mmol·cm^–2·h^–1 compared to that of pure CuO, and the Faradaic efficiencies (FE) reaches 93.2% ± 3.4%. In situ characterization confirms the doping of Ce facilitates the activation and dissociation of interfacial water, which promotes the production of active hydrogen and thus enhances the ammonia production efficiency.

Electrocatalytic chemical oxidation (ECO) is an energy-efficient anodic reaction alternative to the oxygen evolution reaction (OER). ECO lowers the reaction potential and yields higher-value fine chemicals at the anode. The catalyst material plays a crucial role in influencing and determining ECO performance. Enhancing catalyst performance encompasses aspects such as activity, stability, selectivity and cost. Nickel-based electrocatalysts have garnered significant attention for their exceptional performance and widespread use in ECO applications. By modifying nickel-based electrocatalysts, the formation of NiOOH active centers can be encouraged. Strategies such as adjusting size and morphology, doping, introducing defects and constructing heterojunctions are advantageous for enhancing performance. Given the rapid advancements in related research fields, it is imperative to comprehend the mechanisms of nickel-based electrocatalysts in ECO and develop innovative catalysts. This article provides an overview of the modification strategies of nickel-based electrocatalysts, as well as their applications and mechanisms in ECO.

Electrochemical carbon dioxide reduction reaction (CO₂RR) can produce value-added hydrocarbons from renewable electricity, providing a sustainable and promising approach to meet dual-carbon targets and alleviate the energy crisis. However, it is still challenging to improve the selectivity and stability of the products, especially the C₂₊ products. Here we propose to modulate the electronic structure of copper oxide (CuO) through lattice strain construction by zinc (Zn) doping to improve the selectivity of the catalyst to ethylene. Combined performance and in situ characterization analyses show that the compressive strain generated within the CuO lattice and the electronic structure modulation by Zn doping enhances the adsorption of the key intermediate *CO, thereby increasing the intrinsic activity of CO₂RR and inhibiting the hydrogen precipitation reaction. Among the best catalysts had significantly improved ethylene selectivity of 60.5% and partial current density of 500 mA·cm^–2, and the highest C₂₊ Faraday efficiency of 71.47%. This paper provides a simple idea to study the modulation of CO₂RR properties by heteroatom doped and lattice strain.

The electrochemical nitrate reduction reaction (NO₃RR) to ammonia under ambient conditions is a promising approach for addressing elevated nitrate levels in water bodies, but the progress of this reaction is impeded by the complex series of chemical reactions involving electron and proton transfer and competing hydrogen evolution reaction. Therefore, it becomes imperative to develop an electro-catalyst that exhibits exceptional efficiency and remarkable selectivity for ammonia synthesis while maintaining long-term stability. Herein the magnetic biochar (Fe-C) has been synthesized by a two-step mechanochemical route after a pyrolysis treatment (450, 700, and 1000 °C), which not only significantly decreases the particle size, but also exposes more oxygen-rich functional groups on the surface, promoting the adsorption of nitrate and water and accelerating electron transfer to convert it into ammonia. Results showed that the catalyst (Fe-C-700) has an impressive NH₃ production rate of 3.5 mol·h⁻¹·g_cat⁻¹, high Faradaic efficiency of 88%, and current density of 0.37 A·cm⁻² at 0.8 V vs. reversible hydrogen electrode (RHE). In-situ Fourier transform infrared spectroscopy (FTIR) is used to investigate the reaction intermediate and to monitor the reaction. The oxygen functionalities on the catalyst surface activate nitrate ions to form various intermediates (NO₂, NO, NH₂OH, and NH₂) and reduce the rate determining step energy barrier (*NO₃ → *NO₂). This study presents a novel approach for the use of magnetic biochar as an electro-catalyst in NO₃RR and opens the road for solving environmental and energy challenges.