Modifying photocatalyst with defects offers effective pathway to tailor light absorption properties, but may result in more sluggish kinetics. Therefore, enhanced light absorption often could not guarantee increased activity. Here, we report a dual defect strategy to extend light absorption with minimal loss in charge dynamics. Fine-tuned amount of dual defect, i.e., nitrogen defects and single-site copper, is simultaneously generated in polymer carbon nitride(PCN) through in-situ vapor diffusion method. Surface nitrogen defect extends the light absorption to long-wavelength via sub-band absorption. The interaction between nitrogen and single-site copper at certain concentration retains the charge dynamics by making the photogenerated electrons more delocalized through the newly-formed copper-nitrogen bonds. As a result, champion modified PCN exhibits robust hydrogen production activity, roughly 4.5-fold greater than the pristine counterpart in both visible and full light ranges. More intriguingly, this synergism provides PCN with efficient visible light activity even in faint tailing optical absorption region(>450 nm).
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