A membrane electrode assembly of an electrochemical device includes a proton conductive solid electrolyte membrane and an electrode including Ni and an electrolyte material which contains as a primary component, at least one of a first compound having a composition represented by BaZr.sub.1-x1M.sup.1.sub.x1O.sub.3 (M.sup.1 represents at least one element selected from trivalent elements each having an ion radius of more than 0.720 A° to less than 0.880 A°, and 0<x.sub.1<1 holds) and a second compound having a composition represented by BaZr.sub.1-x2Tm.sub.x2O.sub.3 (0<x.sub.2<0.3 holds).

In a sensor element for a limiting-current type gas sensor measuring concentration of NOx in a measurement gas, an inner pump electrode located to face a first internal space communicating, under predetermined diffusion resistance, with a gas inlet through which a measurement gas is introduced from an external space is made of a cermet of a Pt—Au alloy and zirconia, and includes a first portion located on a surface farther from a heater part and a second portion located on a surface closer to the heater part from among surfaces opposing each other in the first internal space, an Au content with respect to the Pt—Au alloy as a whole of the second portion is 0.3 wt % or more smaller than that of the first portion, and a total area of the first portion and the second portion is 10 mm.sup.2 to 25 mm.sup.2.

Provided is a gas sensor element that can be used for relatively long period of time without leading to a problem even in a harsh usage environment. A gas sensor element according to one aspect of the present invention includes a laminate in which an internal space is provided, and a first porous layer arranged so as to face the internal space. The first porous layer is in contact with the first solid electrolyte layer and a side face of the spacer layer that faces the internal space, and has a porosity or 10% or more and 50% or less.

A gas sensor comprises an electrochemical film, a plurality of electrodes coupled with the electrochemical film and a semiconductor wafer coupled with the plurality of electrodes. A passivation layer is formed between the electrochemical firm and the semiconductor wafer and a dielectric layer is coupled between the electrochemical film and the semiconductor wafer.

A sensor element is used to detect the concentration of a predetermined component in a gas. The sensor element includes a sensor element body including a solid-state-electrolyte layer having oxygen-ion conductivity, an outer pump electrode that is disposed on an upper surface, which is one of the surfaces, of the sensor element body, and a porous protective layer that is provided so as to cover at least the outer pump electrode. A spatial layer is provided between the porous protective layer and the sensor element body. The spatial layer includes a first spatial layer between the porous protective layer and the outer pump electrode. The maximum-height roughness Rz of a region of the inner surface of the porous protective layer, the region facing the outer pump electrode, is 50 μm or smaller.

A controller of the gas sensor can perform diagnostic processing of diagnosing a situation of control to the gas sensor in a case that the gas sensor in an operation state is determined to satisfy a predetermined diagnostic condition and adjustment processing of adjusting a condition for controlling the gas sensor in accordance with a result of diagnosis. In the diagnostic processing, a main pump voltage and a diagnostic threshold as a value of a voltage not causing decomposition of NOx in the main pump cell are compared. In the adjustment processing, temperature adjustment processing to cause, in a case that the main pump voltage is diagnosed to be equal to the threshold or more, the main pump voltage to be less than the threshold, at least in a way that the heater part increases the element driving temperature in the operation state by a predetermined increase amount is performed.

In one embodiment, a gas sensor includes a sensing layer having a first region containing PdCuSi, and a second region which is provided outside the first region and contains PdCu.

The present invention provides methods and devices for detecting and distinguishing various types of gas molecules or volatile organic compounds (VOCs), the methods and devices have enhanced sensing ability; namely response magnitude, sensitivity, detection limit and selectivity (i.e., classification capability). In one embodiment, the present invention provides methods and devices for diagnosing a disease in a subject or a health status of a subject through the detection of VOCs indicative of the disease or health status in question from breath of the subject. In one embodiment, the present invention provides methods and devices for detecting the existence of lung cancer or the stage of lung cancer in a subject through the detection of VOCs indicative of the existence of lung cancer from breath of the subject.

Proposed is a gas sensing device. The gas sensing device includes a housing including an opening part through which a target gas to be sensed enters an inner space thereof, a sensor unit disposed in the inner space of the housing, and a connection passage connecting a first opening and a second opening that are formed in the housing such that the first opening and the second opening are open toward the inner space of the housing. According to the present disclosure, there is an effect that the gas sensing device capable of measuring a concentration of a gas with a high response speed and a high accuracy may be provided even if a pressure of a space inside the housing where the sensor unit is disposed increases.

A gas sensor includes a sensor element including an adjustment pump cell and a measurement pump cell, and a control unit including a pump control part. The pump control part performs a startup pump control at a startup of the sensor element, and a steady driving pump control at a steady drive after the startup. In the startup pump control, the pump control part applies, between an inner pump electrode and an outer pump electrode of the adjustment pump cell, a startup voltage of the adjustment pump cell that is higher than a voltage applied in the steady driving pump control; and applies, between an inner measurement electrode and an outer measurement electrode of the measurement pump cell, a startup voltage of the measurement pump cell that is higher than a voltage applied in the steady driving pump control and lower than the startup voltage of the adjustment pump cell.