The oxidation of aldehydes on a copper-based electrocatalyst within a small potential window can produce hydrogen at the anode, thus offering a bipolar hydrogen production system. However, the inherent activity and stability of Cu-based electrocatalysts for aldehyde oxidation are still not satisfactory in practical application. Herein, by coating an ultrathin carbon shell on the copper sphere, an effective and stable formaldehyde oxidation reaction (FOR) can be realized to produce H