Enhanced Performance of Co-doped Antimony Electrode for pH Measurement in Marine Environments

The antimony (Sb) electrode, despite its prevalent use for pH detection in complex environments, suffers from severe potential drift due to poor corrosion resistance, thereby impeding long-term or online applications. Intermetallic compounds show excellent resistance to corrosion and oxidation, presenting a promising avenue for improving the stability of the Sb electrode. Therefore, we fabricate an intermetallic compound-doped Sb electrode by adding various cobalt (Co) contents to improve the stability of the Sb electrode without compromising the inherent pH response. It's observed that the alloy electrode exhibits a significant reduction in surface roughness, corrosion product Sb₂O₃ content, cracks, and Sb exfoliation compared to the pure Sb electrode after the electrochemical tests, and the effect becomes more pronounced as the Co content increases. The electrochemical tests further reveal that the alloy electrode exhibits better corrosion resistance than the pure Sb in various solutions, with the alloy electrode containing 80 at% Sb showing the highest corrosion resistance. Moreover, the alloy electrode containing 80 at% Sb also shows excellent sensitivity and anti-interference ability, high accuracy and reproducibility, low hysteresis, and better long-term stability, especially in seawater. These findings suggest that inexpensive Co doping significantly enhances corrosion resistance, thereby reducing electrode surface alterations and eventually improving the potential stability of pure Sb electrodes without affecting the inherent pH response. Furthermore, the obtained results provide an experimental basis for the long-term operation of the alloy pH electrode in complex environments such as seawater without frequent maintenance.