An electronic nose (e-nose) is an artificial olfaction system that employs an array of gas sensors combined with pattern recognition algorithms to achieve holistic perception and analysis of complex odors. Compared with other human-like sensory modalities, artificial olfaction has long lagged. Accordingly, this review constructs a comprehensive, system-level framework of electronic nose technology from a holistic perspective as follows: ① tracing the development trajectory of electronic nose technology and clarifying the characteristics and evolution of each stage; ② explaining its working principles and system architecture, highlighting the coordination among functional modules; ③ analyzing the sensing elementsthrough their response mechanisms, material properties, and structural design; ④ comparing traditional data processing and pattern recognition methods with advanced intelligent algorithms in terms of differences, applicability, and development trends; ⑤ summarizing practical deployment and challenges based on representative application cases; and ⑥ discussing frontier research directions and identifying industrial bottlenecks. E-nose technology has progressed from mechanical devices and array-based chemical sensors to commercial systems, with material nanostructuring and intelligent algorithms significantly enhancing performance. These advances have enabled applications in disease diagnosis, agriculture, public safety, and energy. Future breakthroughs will depend on coordinated innovations across sensing materials, device design, intelligent algorithms, and system architecture.This review provides a comprehensive, holistic reference for researchers and practitioners, guiding both the study and practical deployment of electronic nose systems.

Protonic ceramic fuel cells (PCFCs) have been recognized as promising power generation devices for future clean energy systems, owing to their relatively low activation energy for proton migration and high energy conversion efficiency. In certain application scenarios, the use of N₂O (a potent greenhouse gas), as an alternative oxidant to air, presents a feasible strategy. Herein, we report for the first time the operation of PCFCs employing N₂O as the oxidant. A hybrid Pr₂Ni_0.6Co_0.4O_4−δ (PNCO-214) catalyst is developed, comprising Ruddlesden–Popper (R–P) structured Pr₄Ni_1.8Co_1.2O_10−δ (PNCO-4310) and fluorite structured Pr₆O₁₁ (PO-611), which synergistically exhibits exceptional catalytic activity toward both N₂O decomposition and the oxygen reduction reaction, achieving a conversion over 92% and an area specific resistance of 1.301 Ω·cm² at 600 °C. Quasi-in-situ temperature-dependent Fourier transform infrared (FTIR) and electrochemical impedance spectroscopy analyses reveal that abundant oxygen vacancies in PNCO-214 facilitate rapid adsorption and dissociation of N₂O into N₂ and O₂, while also promoting the surface exchange kinetics of proton/oxygen during oxygen reduction reaction (ORR). When applied in an anode-supported single cell with PNCO-214 cathode operating under N₂O, outstanding power density and low resistance are achieved, delivering 0.801 W·cm⁻² and 0.245 Ω·cm² at 600 °C. Satisfactory performance is also maintained even when the temperature is reduced to 500 °C. Furthermore, the single cell demonstrates relatively good stability with negligible degradation over 130 h at 600 °C and 0.7 V. These findings underscore the potential of PNCO-214 as a highly effective cathode catalyst for enabling the use of N₂O as a viable oxidant in PCFCs for specific industrial applications.

Ternary strategy is one of the most effective methods to further boost the power conversion efficiency (PCE) of organic photovoltaic cells (OPVs). In terms of high-efficiency PM6:Y6 binary systems, there is still room to further reduce energy loss (E_loss) through regulating molecular packing and aggregation by introducing a third component in the construction of ternary OPVs. Here we introduce a simple molecule BR1 based on an acceptor-donor-acceptor (A-D-A) structure with a wide bandgap and high crystallinity into PM6:Y6-based OPVs. It is proved that BR1 can be selectively dispersed into the donor phase in the PM6:Y6 and reduce disorder in the ternary blends, thus resulting in lower E_loss,non-rad and E_loss. Furthermore, the mechanism study reveals well-develop phase separation morphology and complemented absorption spectra in the ternary blends, leading to higher charge mobility, suppressed recombination, which concurrently contributes to the significantly improved PCE of 17.23% for the ternary system compared with the binary ones (16.21%). This work provides an effective approach to improve the performance of the PM6:Y6-based OPVs by adopting a ternary strategy with a simple molecule as the third component.