Incorporating CdS and anchoring Pt single atoms into porphyrinic metal–organic frameworks for superior visible-light and sunlight-driven H2 evolution

Abstract

Water splitting by photocatalytic semiconductors to produce hydrogen is considered one of the best ways to utilize solar energy. However, the recombination of electron-hole pairs in semiconductors such as cadmium sulfide (CdS) reduces the light-driven reaction efficiency. In addition, nanoparticles (NPs) of semiconductors tend to aggregate, resulting in decreased atom utilization. Rationally building composite photocatalysts by reducing nanoparticle aggregation and maximizing charge transport efficiency is thus seen as an attractive strategy for achieving high hydrogen evolution rates. Herein, we designed a new composite photocatalyst, CdS@PCN-222(Pt), by growing CdS in situ on a metal–organic framework (MOF) containing single Pt atoms. This catalyst exhibits an excellent hydrogen evolution activity of 71645 μmol/gCdS/h under visible light irradiation (λ ≥ 420 nm), which is around 110 times higher than pure CdS. Remarkably, CdS@PCN-222(Pt) also has an extremely high hydrogen evolution activity of 31326 μmol/gCdS/h under direct sunlight irradiation, far surpassing those of reported MOF-based photocatalysts. The charge-separation mechanisms were revealed by spectroscopic measurements, DFT calculations, and single crystal X-ray diffractions. The highly porous structure of PCN-222(Pt) results in the uniform distribution of CdS, and the anchored Pt single atoms achieve photo-induced electron transfer, inhibiting the recombination of photogenerated charge carriers. The results show that the synergistic effects between inorganic semiconductors and MOFs containing anchored single atoms enhance the photocatalytic activity for H2 generation under visible light and even sunlight. As a result, the findings offer important new perspectives that can be utilized in the design of high-performance composite photocatalysts in the future.