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Small-sized particles are usually used as cocatalysts and anchored onto a large-sized photocatalyst for fast charge separation. However, the current problem for the design of photocatalysts is that a high loading of small-sized particles leads to full coverage of photocatalysts, resulting in the decrease of hydrogen production. Here, we propose a different way to construct photocatalytic systems. Large-scale carbon nanotubes with doped nitrogen (N-CNTs) are used to couple with TiO 2 quantum dots. The H 2 yield for our optimized photocatalytic system is ∼146 mmol/g. With further considering the light-induced thermal effect, the H 2 yield reaches up to ∼320.6 mmol/g. Electrochemical and spectroscopic data show that large-sized N-CNTs can offer abundant active sites to realize the rapid carrier separation for tremendously improved hydrogen production.

Cocatalysts in photocatalytic systems play an important role in achieving efficient charge separation. These cocatalysts usually have a small size and are generally anchored onto main catalysts. They are taken as active centers to receive photogenerated electrons for water splitting. However, their high loading concentration usually leads to the degradation of water splitting. Here, we present a different strategy for the design of the main catalyst and cocatalyst. We used small-sized ultrathin cadmium sulfide (CdS) nanosheets as the main catalysts and anchored them onto large-sized Ndoped carbon nanotubes with encapsulated cobalts. The photocatalytic hydrogen production of our optimized composite is ∼21.8 mmol/g, ∼3 times higher than that of pure CdS. Mechanism study shows that photoelectrons can be transferred from CdS to N-doped carbon nanotubes, thus achieving fast charge separation and efficient hydrogen production.

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