Behaviour of a potassium electrode pre-treated with water vapour or gaseous oxygen

Abstract

The electrochemical behaviour of K electrodes in highly dried 0.5 M KPF 6 in propylene carbonate (<0.01 ppm H 2O) was studied. The electrode surface was chemically modified before contacting the electrolyte either by O 2-free H 2O vapour or by dry gaseous O 2; the exposure amounted to 1.2×10 9 and 2.7×10 8 langmuirs, respectively ( ie1.6×10 5 and 3.5×10 4 Pa s). Long-term dependences of the open-circuit potential on the time and interrupted galvanostatic E-t curves proved the existence of firmly adsorbed or chemisorbed passivating layers formed by reaction of K with H 2O vapour or O 2. Their influence on the electrochemical characteristics was apparent even after passage of an anodic charge of 50 mAh cm −2 at 1 mA cm −2 current density.