A new concept of designing photocatalytic systems with reversed configurations

Photocatalytic water splitting is one of the most promising ways to convert solar energy into the chemical one. Generally, the activity of a photocatalytic system composed of photocatalysts and cocatalysts is integrally determined by the efficiencies of basic processes such as light absorption, charge separation and surface catalysis. Conventionally, the nanoparticles of cocatalysts have been loaded on the surface of nanosized/microsized semiconductors.

However, this conventional configuration of photocatalysts has to confront the competition of light harvesting caused by deposited cocatalysts and ineffective interface contacts between photocatalysts and cocatalysts. This greatly retards the enhancement of photocatalytic performances.

Very recently, Prof. Fuxiang Zhang and his colleagues in Dalian Institute of Chemical Physicals, Chinese Academy of Sciences, introduced a reversed configuration of photocatalysts fabricated by depositing nanosized CdS (semiconductor) on the surface of microsized Mo2N hexagonal rods (cocatalyst).

The as-obtained reversed photocatalyst is denoted as Mo2N@CdS. For comparison, the photocatalyst with conventional configurations was fabricated by depositing nanosized Mo2N (cocatalyst) on the surface of bulk CdS (light harvester, photocatalyst), and the corresponding sample is denoted as Mo2N/CdS. The photocatalytic H2 evolution activity of the Mo2N@CdS sample under visible light irradiation is remarkably superior to that of Mo2N/CdS, during which the basic processes such as light absorption, charge separation and surface catalysis between the conventional and reversed configurations have been discussed and compared.

The reversed configuration of photocatalyst in this work shows advantages in light absorption, charge separation and surface catalysis with respect to the conventional configuration. Specifically, the reversed configuration can ensure the preferential light absorption of the CdS semiconductor to avoid the competition of light harvesting caused by the Mo2N cocatalyst. Secondly, much better charge separation is observed for the reversed configuration with respect to the conventional ones. Finally, the electron interactions between CdS and Mo2N and the pore-confined space of CdS particle stack make an effective confinement effect to promote the surface catalysis of Mo2N.

The novel design concept on the reversed configuration can be extended into more other systems, reactions and the fabrication of composites with inner 1D (or 2D) cocatalysts and outer 0D photocatalysts to promote the solar-to-chemical conversion.

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See the article: Lian J, Qi Y, Bao Y, Yin Z, Zhang Y, Yang N, Guan N, Jin S, Li L, Zhang F. Reversed configuration of photocatalysts to exhibit improved properties of basic processes compared to conventional one. Sci China Chem., 2020, 63, DOI: 10.1007/s11426-020-9752-x.

http://engine.scichina.com/publisher/scp/journal/SCC/doi/10.1007/s11426-020-9752-x