Boosting photoelectron transfer by Fermi and doping levels regulation in carbon nitride towards efficient solar-driven hydrogen production

Abstract

The exploration of efficient photosystems with fast carrier dynamics is an important pursuit for solar conversion into hydrogen energy, while tremendous challenges remain since the intrinsic relationship between the band structure and the charge transfer behavior in semiconductors is still elusive. Towards this, P doped graphitic carbon nitride (P-g-C3N4) is fabricated as a prototype photocatalyst with P existing in P − N = C state. Through tuning the content of P to modulate the electronic donor concentration, the Fermi level of g-C3N4 is unidirectionally regulated from below to above the doping level induced by P. And it is revealed that the relative position of Fermi level vs. doping level plays a crucial role in determining the charge migration dynamics, where only a doping state near the Fermi level can act as the most efficient electron trap to prolong carrier lifetime. Accordingly, the precisely tailored P-g-C3N4 achieves a superior apparent quantum efficiency (AQE) of 5.7 % at 420 nm in overall water splitting that is among the highest levels of current photosystems. Our findings offer an innovative strategy for band structure regulation toward efficient photocatalysis.