Room-Temperature Mixed-Potential Type ppb-Level NO Sensors Based on K₂Fe₄O₇ Electrolyte and Ni/Fe–MOF Sensing Electrodes

Abstract

Portable and sensitive mixed-potential type solid-state electrolyte (MPSE) gas sensors can detect exhaled biomarkers in a noninvasive and inexpensive way, which is significant for convenient disease diagnosis and saving medical resources. However, high working temperature is still one of the main bottlenecks for hindering MPSE gas sensors’ applications in disease diagnosis. Here, we, for the first time, developed and fabricated new room-temperature MPSE gas sensors utilizing K2Fe4O7 electrolyte and Ni/Fe–MOF (Ni/Fe clusters are coordinated with 1,4-H2BDC) sensing electrodes (SEs) for the detection of ppb-level NO. Among different MOF SEs, the sensor attached with the Ni–MOF SE presents the highest NO sensitivities. This is attributed to a reducing oxygen reduction reaction activity and enhancing NO electrochemical catalytic reaction activity, verified by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests. In addition, the presented sensor also shows a low detection limit (20 ppb), fast response/recovery characteristic (17 s/6 s to 50 ppb NO), excellent selectivity, acceptable repeatability, and long-term stability of 34 days to NO at 25 °C and 60%RH. Simultaneously, the mechanism of humidity effect on the sensing performance was investigated by EIS and CV tests. Our work provides new insight into the development of room-temperature solid-state electrolyte gas sensors based on the mixed-potential mechanism and enlarges the potential application domain.

Promoted Carbon Monoxide Sensing Performance of a Bi2Mn4O10-Based Mixed-Potential Sensor by Regulating Oxygen Vacancies

“…Such results are further confirmed by the complex impedance plots shown in Figure b. It is clear that the interface resistance value of the 800 °C-sintered electrode is the minimum represented by the narrowed arc in the right at low frequency, which indicates more intense electrode reactions and thus results in preferable sensing performance. , …”

“…2,3 Owing to such high temperatures and complex gas atmospheres in the exhaust environments, many traditional sensors such as optical type and resistive type are not suitable. 4,5 In the past few years, the electrochemical type mixed-potential sensors based on yttria-stabilized zirconia (YSZ) electrolyte exhibited excellent thermal stability under such harsh environments, 6 which have already been investigated in gas detection of afterburning gas pollutants like NO x , 7 NH 3 , 8 and SO 2 . 9 However, limited by the unsatisfactory sensitivity and selectivity of the sensing material under high temperature, YSZ-based sensors remain challenging in further enhancing sensing performance toward CO.…”

“…7,50 ■ CONCLUSIONS In this work, a novel sensing material Bi 2 Mn 4 O 10 with moderate oxygen vacancies was adopted in the mixed-potential CO sensor. The response values toward CO exhibited an identical trend with the proportions of oxygen vacancies of the Bi 2 Mn 4 O 10 sensing material, indicating an important role of oxygen vacancies in enhancing CO sensing properties.…”

“…Since CO mainly comes from the incomplete combustion of fossil fuels, real-time CO detection near the automobile engine is necessary to help the combustion control system monitor CO and thus improve energy efficiency. Nevertheless, there is still no commercial in situ CO detection solution for such application scenarios because exhaust gas monitoring in the tailpipe is usually accompanied by high temperatures above 400 °C, and the gas temperature near the engine outlet is even up to 900 °C. , Owing to such high temperatures and complex gas atmospheres in the exhaust environments, many traditional sensors such as optical type and resistive type are not suitable. , In the past few years, the electrochemical type mixed-potential sensors based on yttria-stabilized zirconia (YSZ) electrolyte exhibited excellent thermal stability under such harsh environments, which have already been investigated in gas detection of afterburning gas pollutants like NO x , NH 3 , and SO 2 . However, limited by the unsatisfactory sensitivity and selectivity of the sensing material under high temperature, YSZ-based sensors remain challenging in further enhancing sensing performance toward CO.…”

Fabrication and Surface Modification of Niobium Metal–Organic Framework Membrane and its Gas Sensing Application

“…Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and X‐ray diffractometry (XRD) were utilized to confirm the chemical composition and binding structure of Nb‐MOF. The FTIR ( Figure a) characteristic band in the high frequency region 3172–2858 cm −1 (N–H stretching vibration), 1703 cm −1 (CO stretching vibration), [ 28 ] 1579 cm −1 (skeleton vibration of benzene ring), [ 29 ] 1345 cm −1 (O–C–O), [ 30 ] 1270 cm −1 , 1098 cm −1 (C–N stretching vibration), and 924–629 cm −1 (C–H) were represents successful construction of Nb‐MOF frame. After the SP embedding, all the main characteristic peak position did not change, while the N–H vibration peak (3172–2858 cm −1 ) intensities were weakened, oppositely, the benzene ring skeleton, C–O, C–N (1579, 1344, 1270 cm −1 ) and the out‐of‐plane bending vibration intensity of benzene ring (766–629 cm −1 ) were slightly enhanced, due to the increased contents of benzene ring, C–N, C–O by embedding SP.…”