E.g. In water electrolysis, Pt serves best for cathode(HER) and RuO for anode(OER), neglecting the scarcity and cost, in terms of efficiency why not just use any two different efficient catalysts for anode and cathode.
There is no need to apply bifunctional electrocatalyst for water electrolyzers, you can use different electrocatalysts. People just want to show their electrocatalyst can work both HER and OER.