Advanced water electrolysis and catalyst stability under discontinuous operation

Raney nickel produced from an Ni/Zn alloy was tested as a catalyst for discontinuously operating alkaline water electrolysers. The cells were loaded with a current density of 400 mA cm−2 at 100°C for 10 h every day. They were then left in the depolarized state without current application for 14 h daily maintaining the temperature of 100°C. Under these very severe conditions the residual zinc partially dissolved from the electrodes. Bipolar cells are thus more strained than monopolar cells. It is therefore appropriate in the bipolar case to either maintain a low protective current during standstill or reduce the temperature. Calculations of the shunt currents in a bipolar cell stack have shown that the behaviour of the central cells in the block must be taken as a measure for the protective effect, the boundary cells being less strained.