Microchip sensor of PdO-NiO electrode for H₂O₂ sensing fabricated with the UV photolithography

An electrochemical microchip sensor was fabricated through the photolithographic process. The metal paste used in the micro-pattern of the sensor chip contained dendritic and spherical Ag-coated Cu powders, which decreased the electrical resistance of the pattern down to 25.69 Ω·cm by forming a network for electron transfer between particles. The electrode materials were dendritic palladium oxide-nickel oxide powders that showed dramatically high surface area. Also, a synergetic effect on the sensing performance between palladium oxide and nickel oxide was observed. The formation of micro-pattern was investigated through optical microscope and field-emission scanning electron microscope. The body resistance of the conductive paste was calculated using the 4-point probe technique, and the electrochemical characteristics of the sensor were analyzed by cyclic voltammetry and chronoamperometry. The fabricated sensor chip exhibited sensing performance for hydrogen peroxide detection with high sensitivity of 641.75 µA mM⁻¹ cm⁻² in a dynamic range between 50 µM and 13 mM. Its long-term stability and high selectivity were also confirmed.