Affecting the H2O electrolysis process in SOECs through modification of NiO/GDC; experimental case of Au-Mo-Ni synergy

•H2O dissociation can be a poisoning step to that of the electrochemical splitting.•Proper modification should achieve a selectively weak interaction of the H2Oads.•3Au-3Mo-Ni/GDC exhibited the highest performance for SOEC H2O splitting.•Au enrichment of the surface and of the bulk phase with Mo improve the electrode.•Au-Mo-Ni synergy promotes significantly the electrochemically active interface.