Insights into the electronic origin of enhancing the catalytic activity of Co3O4 for oxygen evolution by single atom ruthenium

•A single atom decoration strategy was developed to adjust the electronic structure of Co3O4 and activate the catalytic activity for OER.•An advanced atomic layer deposition technology was developed to uniformly deposit isolated Ru single atoms on the surface of Co3O4.•The catalyst activity of Co3O4 was enhanced more than 95.5 times after being triggered by Ru single atoms.•DFT calculations indicated single atom Ru plays the role in adjusting the electronic structure of adjacent Co atoms rather than as the active sites.