The effect of A-site doping in a strontium palladium perovskite and its applications for non-enzymatic glucose sensing

Abstract

The catalytic activity of a strontium palladium perovskite, Sr₂PdO₃, toward non-enzymatic glucose sensing is strongly affected by the Sr²⁺ A-site partial substitution by Ca²⁺ ions; Sr_2−xCa_xPdO₃ with x = 0–0.7. Scanning and transmission electron microscopies (SEM, EDAX and TEM), XRD, XPS, BET and a particle size analyzer were used to investigate the microstructure, morphology, physical–chemical and electrochemical properties of the prepared perovskites. A good-crystalline orthorhombic Sr₂PdO₃ phase was formed as the main phase in all the prepared samples with particle sizes in the range of nanometers as confirmed by XRD. Doping the A-site Sr²⁺ cations with Ca²⁺ ions in the Sr₂PdO₃ perovskite leads to the enhancement of the elecrocatalytic activity towards non-enzymatic glucose sensing showing the highest elecrocatalytic activity in the case of Sr_1.7Ca_0.3PdO₃. This may be attributed to the higher free volume in the crystal lattice, enhanced content and mobility of surface lattice oxygen and distorted stabilized perovskite structure leading to higher catalytic activity of the prepared perovskites. In addition, synergistic interactions were achieved between Sr²⁺ and Ca²⁺ in the A-site and Pd²⁺ ions in the B-site resulting in improved surface activity and a stabilized structure. As a result, greater ionic and electronic conductivity and enhanced catalytic activity were achieved upon doping. Graphite/Sr_1.7Ca_0.3PdO₃ as a free enzymatic glucose sensor exhibited good stability, a low detection limit, high sensitivity, good selectivity even in the presence of common interferents, applicability in real sample analysis and anti-interference ability.