To realise sustainable hydrogen economy, corrosion-resistant non-noble metal catalysts are needed to replace catalysts based on noble metals. The combination of passivation elements and catalytically active elements is crucial for simultaneously achieving high corrosion resistance and high catalytic activity. Here, we investigated the self-selection/reconstruction characteristics of multi-element (nonary) alloys that could automatically redistribute suitable elements and rearrange surface structures under the target reaction conditions. We found the following synergetic effect (i.e. cocktail effect) among the elements: Ti, Zr, Nb, and Mo significantly contribute to passivation, whereas Cr, Co, Ni, Mn, and Fe enhance the catalytic activity. Practical water electrolysis experiments showed that the self-selected/reconstructed multi-element alloy demonstrates high performance in proton exchange membrane (PEM)-type water electrolysis without obvious degeneration during stability tests, verifying the alloy’s resistance to corrosion in a practical PEM electrolyser.