In this article, we report a facile electrochemical method to modify anatase TiO₂ by cathodically biasing TiO₂ in an ethylene glycol electrolyte. The resulting black TiO₂ is highly stable with a significantly narrower bandgap and higher electrical conductivity. Furthermore, largely improved photoconversion efficiency (increased from 48% to 72% in the visible region, and from nearly 0% to 7% in the UV region), photocatalytic efficiency, and charge-storage capability (∼42 fold increase) are achieved for the treated TiO₂.