Ir/Ir(OH)_x-pH Electrodes In The Research Of Seawater And Freshwater:Developments And Applications

Resulting from the rising levels of atmospheric carbon,the huge carbon pool-ocean has absorbed amounts of CO2.Ocean Acidification is becoming a global problem.And Lake Eutrophication is severe common in recent years.Several studies have shown that pH of lakes is closely related with the reproduction of algae.It is very significant for the development of ocean observation and environment monitoring fields to measure pH values online accurately and effectively.In this study,Ir/Ir(OH)x pH electrode was prepared by a one-step electrochemical method at room temperature.Scanning electron microscope(SU-70 SEM)observation revealed that it was coated with small particles with a diameter of 50-200nm.pH standard solutions prepared by 3.5%NaCl and commercial pH standard solutions were used as calibration solutions to model seawater and freshwater environment.Results shows that the electrode is characterized by ideal Nernst response(k:59,52-56.14mV/pH,R2>0.99),fast response,good stability and long lifespan in these two environments.And in freshwater,the response ranged from 2 to 12.This paper focused on the application of the pH sensor.With the pH electrodes integrated on,the hand-made electrochemical sensor was applied in the Newport Harbor areas.It was strapped to a Sea-Bird 911 plus CTD for testing its accuracy.After data processing,results reflect that the pH value measured by our sensor is very close to the data given by CTD,with a difference value of less than 0.06.Our sensor also shows a better data matching degree in down and-up process.Subsequently,this sensor was used in Taihu,with a continuous measuring from 6:00-22:00 and profile measuring of every 2 hours.It indicates that pH value was high in the daytime,while it decreases at night.Furthermore,?pH of lake surface and bottom is 0.1-4 and it has a huge difference at different time periods.With analyzing the related factors,it may be caused by biological activity,eutrophication and layering phenomenon.Overall,the Ir/Ir(OH)x-pH sensor could be used in both seawater and freshwater,and will have broad application prospects in the Ocean Acidification and Lake Eutrohication.