For realizing efficient solar to hydrogen energy conversion based on photocatalytic technology, it is important to explore a photocatalyst with wide-range solar absorption and high electron–hole separation efficiency. With a built-in electric field, the recently synthesized Janus MoSSe is intrinsically beneficial for promoting the separation of photo-generated electrons and holes. Thus in this work, we examine the possibility of MoSSe as an efficient water-splitting photocatalyst and the effects of isotropic and uniaxial strains by the first-principles calculations. It is interesting to find that MoSSe exhibits pronounced visible-light absorption efficiency, proper valence and conduction band positions for initializing the redox reactions of H₂O, and high carrier mobilities. Moreover, the band gap of MoSSe is decreased and the direct–indirect band gap transition occurs upon tensile strain, which can not only extend the light absorption range, but also reduce the recombination of photo-generated carriers. Furthermore, H₂O molecules adsorb more strongly on the MoSSe monolayer surface than on the MoS₂ surface, which is also beneficial for the surface water-splitting reactions. These insights provide eloquent evidence that the Janus MoSSe monolayer is potentially an efficient and wide solar-spectrum water-splitting photocatalyst.

Among the many novel photocatalytic systems developed in very recent years, plasmonic photocatalytic composites possess great potential for use in applications and are one of the most intensively investigated photocatalytic systems owing to their high solar energy utilization efficiency. In these composites, the plasmonic nanoparticles (PNPs) efficiently absorb solar light through localized surface plasmon resonance and convert it into energetic electrons and holes in the nearby semiconductor. This energy transfer from PNPs to semiconductors plays a decisive role in the overall photocatalytic performance. Thus, the underlying physical mechanism is of great scientific and technological importance and is one of the hottest topics in the area of plasmonic photocatalysts. In this review, we examine the very recent advances in understanding the energy transfer process in plasmonic photocatalytic composites, describing both the theoretical basis of this process and experimental demonstrations. The factors that affect the energy transfer efficiencies and how to improve the efficiencies to yield better photocatalytic performance are also discussed. Furthermore, comparisons are made between the various energy transfer processes, emphasizing their limitations/benefits for efficient operation of plasmonic photocatalysts.

Ag₂O microcrystals with different morphologies have been successfully synthesized by using various complexing agents. To achieve kinetic control of the growth of the Ag₂O microcrystals, [Ag(NH₃)₂]⁺ complexing ions are required to restrict the release rate of silver ions before adding NaOH solution. The complexing anions play an important role in the growth process of the Ag₂O microcrystals. This kinetic control leads to five morphologies of Ag₂O microcrystals (cubic, octahedral, rhombic dodecahedra, polyhedra with 18 faces and rhombicuboctahedral), which exhibit facet-dependent photocatalytic activity for the degradation of methyl orange (MO) under visible light irradiation. The cubic Ag@Ag₂O photocatalyst with exposed {100} facets showed the greatest activity of all the other morphologies of the photocatalysts. The mechanism of dramatic enhancement of the photocatalytic activity of Ag@Ag₂O with exposed {100} facets was discussed in detail from three aspects, including the highest surface energy of the {100} facet, the larger difference value between the weighted average of the effective mass of holes and electrons along the [100] direction, and the suitable redox potentials of the (100) surface.