The construction of a p-n heterojunction is an efficient strategy to resolve the limited light absorption and serious charge-carrier recombination in semiconductors and enhance the photocatalytic activity. However, the promotion effect is greatly limited by poor interfacial charge transfer efficiency as well as reduced redox ability of charge carriers. In this work, we demonstrate that the embedding of metal Pd into the interface between n-type C3N4 and p-type Cu2O can further enhance the interfacial charge transfer and increase the redox ability of charge carriers through the design of the C3N4-Pd-Cu2O stack nanostructure. The embedded Pd nanocubes in the stack structure not only trap the charge carriers from the semiconductors in promoting the electron-hole separation but also act as a Z-scheme "bridge" in keeping the strong reduction/oxidation ability of the electrons/holes for surface reactions. Furthermore, Pd nanocubes also increase the bonding strength between the two semiconductors. Enabled by this unique design, the hydrogen evolution achieved is dramatically higher than that of its counterpart C3N4-Cu2O structure without Pd embedding. The apparent quantum efficiency (AQE) is 0.9% at 420 nm for the designed C3N4-Pd-Cu2O. This work highlights the rational interfacial design of heterojunctions for enhanced photocatalytic performance.

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The combination of upconversion nanocrystals with a wide-bandgap semiconductor is an efficient strategy to develop near-infrared (NIR)-responsive photocatalysts. The photocatalytic activity of the hybrid structures is greatly determined by the efficiency of the energy transfer on the interface between upconversion nanocrystals and the semiconductor. In this work, we demonstrate the interface design of a NaYF:Yb,Tm-BiOCl hybrid structure based on the choice of suitable BiOCl facets in depositing NaYF:Yb,Tm upconversion nanocrystals. It was found that the selective deposition of NaYF:Yb,Tm nanocrystals on the BiOCl(110) facet can greatly enhance the photocatalytic performance in dye degradation compared with the sample with NaYF:Yb,Tm nanocrystals loaded on the BiOCl(001) facet. Two effects were believed to contribute to this enhancement: (1) a stronger UV emission absorption ability of the BiOCl(110) facet from NaYF:Yb,Tm in generating more photo-induced charge carriers resulted from the narrower bandgap; (2) a shorter diffusion distance of photogenerated charge carriers to the BiOCl(110) reactive facet for surface catalytic reactions owing to the spatial charge separation between different facets. This work highlights the rational interfacial design of an upconversion nanocrystal-semiconductor hybrid structure for enhanced energy transfer in photocatalysis.

Integration of plasmonic metal and cocatalyst with semiconductor is a promising approach to simultaneously optimize the generation, transfer, and consumption of photoinduced charge carriers for high-performance photocatalysis. The photocatalytic activities of the designed hybrid structures are greatly determined by the efficiencies of charge transfer across the interfaces between different components. In this paper, interface design of Ag-BiOCl-PdO hybrid photocatalysts is demonstrated based on the choice of suitable BiOCl facets in depositing plasmonic Ag and PdO cocatalyst, respectively. It is found that the selective deposition of Ag and PdO on BiOCl(110) planes realizes the superior photocatalytic activity in O evolution compared with the samples with other Ag and PdO deposition locations. The reason was the superior hole transfer abilities of Ag-(110)BiOCl and BiOCl(110)-PdO interfaces in comparison with those of Ag-(001)BiOCl and BiOCl(001)-PdO interfaces. Two effects are proposed to contribute to this enhancement: (1) stronger electronic coupling at the BiOCl(110)-based interfaces resulted from the thinner contact barrier layer and (2) the shortest average hole diffuse distance realized by Ag and PdO on BiOCl(110) planes. This work represents a step toward the interface design of high-performance photocatalyst through facet engineering.

An Ag2S@MoS2 core–shell nanowire heterojunction, facilely synthesized by simultaneous sulfuration of Ag nanowires (NMs) and growth of MoS2, is used as a model system to disclose how the surface and interface structures influence the photocatalytic activity. The Ag2S@MoS2 NWs with different loading amounts of MoS2 are used as photocatalysts for H2 production. It is found that the highest photocatalytic activity is realized by a moderate loading amount of MoS2. A lower loading amount of MoS2 not only reduces the interfacial contact for insufficient electron–hole separation but also decreases the number of catalytic active sites for H2 production, while a higher loading amount of MoS2 increases the light‐shielding effect of Ag2S and extends the distance of electron transfer to the catalytic active sites for H2 production. Furthermore, with the same loading amount of MoS2, Ag2S@MoS2 NWs also exhibit superior H2 production activity in comparison with pre‐Ag2S@MoS2 NWs with MoS2 grown on pre‐synthesized Ag2S nanowires. The proposed reason is that the simultaneous sulfuration of Ag nanowires and growth of MoS2 results in an intimate contact between Ag2S and MoS2 for smooth interfacial charge transfer, while the two‐step synthetic method leads to a lower quality of the MoS2‐Ag2S interface and thus poor interelectron transfer. This work highlights the importance of a rational surface and interface design of semiconductor heterojunctions for realizing high‐performance photocatalytic applications.