In both reaction mechanisms, on the other hand, the differences in catalytic behaviour of various catalysts toward HER are not stated, such as the rationale for Pt being superior to Ag. The defect of these mechanisms arising from this indiscrimination appears most evidently in the designing future catalysts for HER, so far, all of effective catalysts were developed by empirical method, so that, both catalytic mechanisms are of no use for predicting the catalytic activity of various catalysts for HER.