Most transition metal oxides undergo in situ catalyst reconstruction during the oxygen evolution reaction in alkaline media. The reconstruction results in a positive or a negative effect on the catalyst performance. In article number 2101324, Alberto Vomiero and co-workers report the in situ electrochemical transformations of NiMoO 4@ Co 3 O 4, facilitated by Mo leaching, which is one of the centers of active sites responsible for higher catalytic activity.