Enhancement Mechanism of Photocatalytic Hydrogen Production Activity of CeO₂/CdS by Morphology Regulation

Abstract

The morphology of the catalyst is one of the important factors affecting the photocatalytic activity. Being highly specific exposed to different crystal facets has a significant effect on photocatalysis. Thereby, well-interpreted examples of CeO 2 , dominated by ( 311) and ( 220), respectively, are presented to explore the reactivity of photocatalyzed special exposed crystal surfaces in photocatalyzed hydrogen evolution. The photocatalytic activity of NR-CeO 2 (311) was testified to be remarkably higher than NF-CeO 2 (220). Further electrochemical detection studies have confirmed that the difference in activity is not only due to the different morphologies of the materials but also controlled by the different exposing facets, resulting in photogenerated carriers and effective spatial separation. When the mass proportion of NR-CeO 2 and CdS is 1:4, the photocatalytic activity of NR-CeO 2 /CdS is highest (about 444 μmol•g −1 •h −1 ), which is about 19.7 times stronger than that of pure CdS. The reaction mechanism was further confirmed by the DFT calculation. Effective separation of photogenerated carriers and specific rod-like shapes and surface atomic arrangements contribute to the high activity of well-designed CeO 2 /CdS photocatalysis. Combined with the experiment and characterization, the regulation mechanism of the CeO 2 morphology and crystal surfaces with different morphologies was proposed, and the photogenerated carrier transport was evaluated. The results show that the morphology and crystal facets have great influence on the photocatalytic activity of CeO 2 .

Urchin-like TiO2/CdS Nanoparticles Forming an S-scheme Heterojunction for Photocatalytic Hydrogen Production and CO2 Reduction

“…The work function is essential for the study of interfacial charge transfer, which is calculated after the simulation by the vacuum level and Fermi level of T (200) and CE (101) shown in the graphs (Figure a,b). By calculating the formula Φ = E vacuum – E Fermi , the corresponding work function for TiO 2 (200) and CdS (101) can be obtained as 5.063 and 5.554 eV, and the Fermi levels are −3.958 and −3.222 eV, respectively.…”

Nanostructured CeO2 photocatalysts: optimizing surface chemistry, morphology, and visible-light absorption

“…5). 40 Another type of solution-phase synthesis is the sol-gel method, where a colloidal suspension of particles undergoes a hydrolysis reaction to form metal-oxygen-metal bonds. Eventually these particles grow and condense to form a 3D, porous network of nanoparticles with liquid trapped in the pores.…”

“…A recent study concurs that CdS → CeO 2 electron transfer is the dominant mechanism (i.e., not a Z-scheme), and finds the photocatalytic activity of preferential 〈311〉 CeO 2 nanorods is significantly higher than that of 〈220〉 CeO 2 nanosheets. 40 Many other nitrides, 61,62 oxides, [63][64][65] or sulfides 39,61,66 have been paired with CeO 2 for photocatalytic HER as a means to operate as either Z-scheme or type-II heterojunctions depending on the band alignment (Table 2). Regardless of where the photoelectron transfers, the result is reduced photoluminescent (PL) recombination upon forming the heterojunction.…”

Dual Active Site Mediated Photocatalytic H2 Evolution through Water Splitting Using CeO2/PPy/BFO Double Heterojunction Catalyst

“…Among traditional metal oxide semiconductors, ceria (CeO 2 ) competes with benchmark materials like TiO 2 and ZnO. This is attributed to its high photostability, robust framework, easily modifiable Ce 4+ /Ce 3+ redox properties, resistance to photocorrosion, nontoxic nature, and exceptional thermal. , Nevertheless, the solar energy utilization efficiency of CeO 2 is very limited due to its inherent wide energy gap (3.2 eV). This limitation may be resolved by adhering to different types of p–n heterojunction, Z-scheme, type II, and S-scheme heterostructures. − For example, Lin et al successfully fabricated the CeO 2 /TiO 2 heterojunction which exhibited a high photocurrent density and 4.5-fold augmentation in the rate of photoelectrochemical H 2 generation (17.86 μmol h –1 ) compared to pristine TiO 2 nanotubes due to enhanced visible light harvesting and facile interfacial charge carrier separation owing to the presence of Ce(IV)/Ce(III) reversible redox pair in CeO 2 .…”

“…This is attributed to its high photostability, robust framework, easily modifiable Ce 4+ /Ce 3+ redox properties, resistance to photocorrosion, nontoxic nature, and exceptional thermal. 30,31 Nevertheless, the solar energy utilization efficiency of CeO 2 is very limited due to its inherent wide energy gap (3.2 eV). This limitation may be resolved by adhering to different types of p−n heterojunction, Z-scheme, type II, and S-scheme heterostructures.…”