Karthikeyan Hariharan, Koushik Kosanam, Carina Götz, Mark Bruns, Thomas Böhm, Philippe Marcus, narasi sridhar, Sannakaisa Virtanen
A mechanism for transpassive film formation in pure Ni in a sulfate environment is proposed based on in situ Raman spectroscopy and electrochemistry-coupled respirometry. Based on potentiostatic respirometry on pure Ni in 0.1 M K 2 SO 4 , there is a characteristic time-delay before the onset of oxygen evolution, coinciding with the onset of transpassive film formation upon stepping the potential from passive into the transpassive regime. At the same time, in situ Raman spectroscopy revealed that the transpassive film comprised of NiOOH. It reduced back without any time-delay after returning to open-circuit conditions to a passive Ni(OH) 2.