Effect of oxygen terminated surface of boron-doped diamond thin-film electrode on seawater salinity sensing

•Oxygen terminated BDD electrodes demonstrate high sensitivity and great long-term stability in seawater salinity detection.•The high sensitivity of the oxygen terminated BDD electrodes can be ascribed to the improved Cdl which is enhanced by C-O functional group.•Oxygen terminated BDD electrodes display outstanding stability thanks to the stable exist of surface oxygen.•Excellent oxygen terminated BDD electrodes promise potential application in practical seawater salinity detection.