Photocatalytic cofactor regeneration involving triethanolamine revisited: the critical role of glycolaldehyde

•Oxygen-assisted photodegradation of triethanolamine leads to the formation of glycolaldehyde reduces cofactor molecules (NADH+).•Back oxidation of the newly formed NADH is minimised by spatial and temporal decoupling redox processes.•Triethanolamine maintains the alkalinity of the mixture ensuring reduction power of glycolaldehyde.