Confinement effects in space-confined catalysts are attracting attention due to their advantages, like size control, unique nanoscale chemical environments and designable nature of the active sites. There are rarely works on the direct confirmation of confinement effects because of restrictions of nanoscale confined space. Herein, we report the fabrication of a novel structure that is composed of NiO nanoparticles confined in SnO₂ nanocoils (I-NiSnNCs) via atomic layer deposition (ALD). The I-NiSnNCs displayed higher sensing performance towards hydrogen than the NiO–SnO₂ film, NiO outside NiSnNC and NiO both outside and inside NiSnNC sensors. The I-NiSnNC sensor shows a response to about 7 to 50 ppm H₂ with a 2.4 s response time and 4.2 s recovery time at 260 °C and excellent repeatability. The synergistic effect of interfacial sites is attributed to the reaction between adsorbed H on NiO and adsorbed O at interfacial active sites. The “funneling effect” formed because the enrichment effect of hydrogen on the NiO surface is higher than that of the gas state as the adsorbed H quickly reacts at interfacial active sites. The enrichment effects of H₂ lead to high sensing performance to H₂, and the high reactivity of H₂ at interfacial active sites leading to rapid transfer of electrons is responsible for the high response/recovery performance. The gas sensor offers a new way to directly confirm the confinement effect. And the confinement effects in return give a novel way to design sensing materials.

Supercapacitors are a kind of energy storage device that lie between traditional capacitors and batteries, characterized by high power density, long cycle life, and rapid charging and discharging capabilities. The energy storage mechanism of supercapacitors mainly includes electrical double-layer capacitance and pseudocapacitance. In addition to constructing multi-level pore structures to increase the specific surface area of electrode materials, defect engineering is essential for enhancing electrochemical active sites and achieving additional extrinsic pseudocapacitance. Therefore, developing a simple and efficient method for defect engineering is essential. Atomic layer deposition (ALD) technology enables precise control over thin film thickness at the atomic level through layer-by-layer deposition. This capability allows the intentional introduction of defects, such as vacancies, heteroatom doping, or misalignment, at specific sites within the material. The ALD process can regulate the defects in materials without altering the overall structure, thereby optimizing both the electrochemical and physical properties of the materials. Its self-limiting surface reaction mechanism also ensures that defects and doping sites are introduced uniformly across the material surface. This uniform defect distribution is particularly profitable for high surface area electrodes in supercapacitor applications, as it promotes consistent performance across the entire electrode. This review systematically summarizes the latest advancements in defect engineering via ALD technology in supercapacitors, including the enhancement of conductivity and the increase of active sites in supercapacitor electrode materials through ALD, thereby improving specific capacitance and energy density of the supercapacitor device. Furthermore, we discuss the underlying mechanisms, advantages, and future directions for ALD in this field.

The flocculation of small surficial groups on pristine CNCs (carbon nanocoils) bundles limit their application. In this study, we designed and fabricated novel array CNCs with a surficial decoration of polyaniline (PANI) using in situ methods. Atomic layer deposition (ALD) and chemical vapor deposition (CVD) methods were employed to fabricate the highly pure array CNCs. The array CNCs decorated with ultra-thin PANI were confirmed by different characterizations. Furthermore, this material displayed a good performance in its detection of formaldehyde. The detection results showed that the CNCs coated with PANI had a low limit of detection of HCHO, as low as 500 ppb, and the sensor also showed good selectivity for other interfering gases, as well as good repeatability over many tests. Furthermore, after increasing the PANI loading on the surface of the CNCs, their detection performance exhibited a typical volcanic curve, and the value of the enthalpy was extracted by using the temperature-varying micro-gravimetric method during the process of detection of the formaldehyde molecules on the CNCs. The use of array CNCs with surficial decoration offers a novel method for the application of CNCs and could be extended to other applications, such as catalysts and energy conversion.