Photocatalytic organic syntheses are often limited by their low system efficiency and product selectivity. We demonstrate herein that intermolecular hydrogen transfer from isopropanol to acetone can be achieved efficiently on the surfaces of NaTaO3 photocatalysts, on which 2-hydroxyisopropyl radicals are produced selectively from both oxidation and reduction half-reactions and then coupled to form 2,3-dimethyl-2,3-butanediol. Such a process effectively increases the total reaction efficiency. We also found that the two half-reactions occur at different crystal facets and display a remarkably promotive interaction, which dramatically speeds up the reactions by one order of magnitude and significantly restrains side reactions. The sodium ions on the NaTaO3 surfaces play an important role in the promotive effect, likely facilitating the proton transfer between the oxidation and reduction sites. These factors make the production rate of 2,3-dimethyl-2,3-butanediol reach a very high level (10.87 mmol g−1 h−1), emphasizing the potential of photocatalytic hydrogenation and dehydrogenation in improving system efficiency of photocatalytic organic syntheses.