Core-Shell Nanostructures of Graphene-Wrapped CdS Nanoparticles and TiO2 (CdS@G@TiO2): The Role of Graphene in Enhanced Photocatalytic H2 Generation

Abstract

Aiming to achieve enhanced photocatalytic activity and stability toward the generation of H2 from water, we have synthesized noble metal-free core-shell nanoparticles of graphene (G)-wrapped CdS and TiO2 (CdS@G@TiO2) by a facile hydrothermal method. The interlayer thickness of G between the CdS core and TiO2 shell is optimized by varying the amount of graphene quantum dots (GQD) during the synthesis procedure. The most optimized sample, i.e., CdS@50G@TiO2 generated 1510 µmole g−1 h−1 of H2 (apparent quantum efficiency (AQE) = 5.78%) from water under simulated solar light with air mass 1.5 global (AM 1.5G) condition which is ~2.7 times and ~2.2 time superior to pure TiO2 and pure CdS respectively, along with a stable generation of H2 during 40 h of continuous operation. The increased photocatalytic activity and stability of the CdS@50G@TiO2 sample are attributed to the enhanced visible light absorption and efficient charge separation and transfer between the CdS and TiO2 due to incorporation of graphene between the CdS core and TiO2 shell, which was also confirmed by UV-vis, photoelectrochemical and valence band XPS measurements.

Enhanced Photoelectrochemical Water Splitting at Hematite Photoanodes by Effect of a NiFe-Oxide co-Catalyst

“…The most appropriate loading for the co-catalyst was 12 µg cm −2 with an enthalpy efficiency of 0.528% in the bias-assisted region at −0.6 V. The throughput efficiency increased as the bias voltage became larger, due to an enhancement of the overall photocurrent at high bias voltages, as shown in the inset of Figure 5. Photocurrents are similar to those recently reported for advanced core-shell nanostructure-based cells [73]. The throughput efficiency calculation is very similar to the efficiency determination of a conventional (dark) electrolyzer, where the total energy output is divided by the total energy input.…”

“…The best throughput efficiency recorded at the reversible potential was 1.7%. cells [73]. The throughput efficiency calculation is very similar to the efficiency determination of a conventional (dark) electrolyzer, where the total energy output is divided by the total energy input.…”

Type II Heterojunction Formed between {010} or {012} Facets Dominated Bismuth Vanadium Oxide and Carbon Nitride to Enhance the Photocatalytic Degradation of Tetracycline

“…As shown in Figure 4 b, positive tangents in Mott–Schottky plots of {010}BiVO 4 , {012}BiVO 4 , and g-C 3 N 4 were observed, which reveals the n-type semiconductor characteristics of these prepared samples [ 42 , 43 ]. For n-type semiconductors, the conduction band (E CB ) is considered very close to the flat band [ 44 , 45 ]. Hence, by calculating the intercept of the tangent line in Mott–Schottky plots, the conduction band energy potentials of {010}BiVO 4 , {012}BiVO 4 , and g-C 3 N 4 were estimated as −0.45, −0.24 and −0.07 V vs. NHE at pH = 0, respectively.…”

Editorial Catalysts: Special Issue on Recent Advances in TiO2 Photocatalysts

“…The heterogeneous photocatalytic process, as well as new TiO 2 -based materials applied in biomedical fields, energy storage, and energy conversion devices, can contribute to improving the quality of the natural environment [9][10][11]. High-efficiency TiO 2 -based photocatalysts are also successfully used in photocatalytic water splitting and photoconversion, providing a low-cost and environmentally friendly production method of clean fuels [12,13]. Separation of the photocatalyst particles after treatment is the main disadvantage of the suspended process.…”

“…However, due to the large energy band gap, its activity in the range of natural solar light is quite limited. For this reason, the development of new TiO 2 -based photocatalysts active in the visible range has become a new research trend [1,3,6,13,[15][16][17][18][19]. The effectivity can also be improved by modifying TiO 2 with noble metals [2,13,15] or by Ti 3+ -self-doped TiO 2 modification [11].…”