Photo-generated charges escape from P+ center through the chemical bridges between P-doped g-C3N4 and RuxP nanoparticles to enhance the photocatalytic hydrogen evolution

Abstract

Many researches have shown that phosphorus doping can affect the photocatalytic activity, mainly because the incorporation of P atoms significantly alters the electronic, surface chemical, and properties of different semiconductors. However, excessive phosphorous doping will form the accumulation and recombination center of photo-generated charge carrier, thereby limiting the activity of photocatalytic reactions. In this work, we successfully prepared excessive P-doping g-C3N4 with ruthenium phosphide nanoparticles (RuxP/PCN), which had excellent performance of hydrogen evolution (1.94 mmol g−1 h−1). Specifically, C was replaced by P in the melon units of PCN and positive charge center (P+) was introduced, reinforcing the chemical connection between PCN and RuxP. In fact, excessive P+ centers became the traps and stacking centers of photo-generated carriers. However, due to the introduction of RuxP NPs, the accumulated charges in the P+ centers through the chemical bridges between PCN and RuxP NPs migrated to surface and then separated on RuxP NPs. Our research illustrates the mechanism of the accumulated charges caused by excessive phosphorus doping migrate to the surface and separate on phosphides, which can prolong the lifetime of photo-generated carriers. This result promoted the significant increase of photocatalytic hydrogen production activity. Our research clarifies the mechanism of excessive phosphorus doping and phosphides act on this photocatalytic system, which will provide a new way to design a photocatalytic system with higher HER performance.