Fast Response, Highly Sensitive and Selective Mixed-Potential H₂ Sensor Based on (La, Sr)(Cr, Fe)O_3-δ Perovskite...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Sensing

Background:

• Development of selective and sensitive hydrogen (H₂) sensors is crucial for safety and industrial process monitoring.
• Mixed-potential sensors offer a promising alternative to traditional electrochemical sensors for gas detection.

Purpose of the Study:

• To develop and characterize a novel planar mixed-potential type sensor for H₂ detection.
• To evaluate the sensor's performance, including response, selectivity, and response/recovery times.
• To investigate the sensing mechanism and its relation to electrode material properties.

Main Methods:

• Fabrication of a planar sensor with La_0.8Sr_0.2Cr_0.5Fe_0.5O_3-δ sensing electrode, yttria-stabilized zirconia solid electrolyte, and Pt reference electrode.
• Electrochemical measurements to assess mixed-potential mechanism and sensor response.
• Testing sensor performance at various H₂ concentrations (20-1000 ppm) and temperatures (up to 450 °C).
• Evaluation of selectivity against interfering gases like CH₄, C₃H₈, CO, NO₂, and NH₃.

Main Results:

• The sensor exhibited a high and repeatable response (-143.6 mV for 1000 ppm H₂ at 450 °C).
• Linear and logarithmic responses were observed in the 20-100 ppm and 100-1000 ppm ranges, respectively.
• Fast response (4 s) and recovery (24 s) times were achieved at 450 °C for 500 ppm H₂.
• Excellent selectivity to H₂ over other tested gases was demonstrated.
• Sensor performance correlated with the electrocatalytic activity of the perovskite electrode for H₂ oxidation.

Conclusions:

• The developed La_0.8Sr_0.2Cr_0.5Fe_0.5O_3-δ based mixed-potential sensor shows excellent performance for H₂ detection.
• High electrocatalytic activity of the perovskite electrode contributes to efficient H₂ sensing at higher concentrations.
• Further optimization may be needed to address limitations at lower H₂ concentrations potentially due to gas diffusion.