The role of electrode structure and surface texture in the performance of gas evolving electrodes

The literature on gas-evolving electrodes is reviewed. Cell voltage measurements are reported for an undivided cell in NaOH at 70° C in which the cathode was mild steel plate, mild steel mesh or composites of both these materials. The anode was Ni-plated mild steel sheet or mesh. Variation in the structure of one electrode, leaving the other unchanged allowed changes in overvoltage to be measured. It is shown that substantial voltage reductions can be obtained using multiplex electrode structures and that these are mainly explicable in terms of specific surface areas. Sheet electrodes are seen to be more efficient than mesh ones on this basis however. It is shown that sheet electrodes with very high specific surface areas show significantly higher overvoltages than electrodes of low specific area and this surprising result is interpreted in terms of bubble entrapment.