Hydrogen Production from Water Splitting with 2,4,6-Triphenylpyrylium Modified on B-Doped N-Deficient Carbon Nitride Nanostructures

A solar-driven hydrogen production process using a graphitic carbon nitride (CN) photocatalyst is an ideal future clean energy source. However, hydrogen production efficiency in the CN photocatalytic system is still limited due to rapid electron–hole (e−/h+) recombination. Herein, we report an efficient photocatalyst BCN-TPP by introducing 2,4,6-triphenylpyrylium (TPP) to boron-doped nitrogen-deficient carbon nitride (BCN) through π–π interaction and π–cation interaction. The as-prepared photocatalyst shows increased visible light absorption and narrow band gap, enhancing the separation of photogenerated e–/h+ pairs. TPP acts as a redox mediator under visible light excitation that can accept electrons from BCN, and then transfer them to the Pt cocatalyst. Photoluminescence (PL), electron paramagnetic resonance (EPR), and other electrochemical studies have exhibited that introducing a TPP mediator significantly enhances photogenerated charge carrier separation. BCN-TPP (10 wt % TPP) nanostructures achieved the photocatalytic H2 generation rate of 110.33 μmol h–1 at visible light illumination (λ ≥ 420 nm), which is 9.59 times higher than that of pristine C3N4 (11.50 μmol h–1) and the apparent quantum efficiency (AQE) of 6.03% at 450 nm. Moreover, BCN-TPP shows the stability of H2 evolution over 4 cycles without any significant decline. This study represents an approach for designing efficient nanoheterostructured photocatalysts for hydrogen production from water splitting.