Analysis of Time‐Variation Effects in Water Electrolyzers

An analysis of unipolar electrolyzer equipment is reported which allows estimation of the different contributions to cell voltage of the reversible potential, of electronic and ionic ohmic resistance, and of the electrode overvoltages. A technique is described which allows performance data for a commercial electrolyzer to be decomposed to give the ohmic resistance contribution as well as the sum of the Tafel slopes for the anodic and cathodic processes. Substantial time variation of both the anode and cathode overvoltages was observed, with the rate and magnitude of this variation being dependent on current density. In light of these results, appropriate methods for long‐term evaluation of new electrode materials are discussed, and a reliable long‐term‐test cell is described. Representative data obtained on prolonged operation of cathodic and anodic electrode samples are reported.