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Graphitic carbon nitride (g-C 3 N 4 ) has aroused intense expectations owing to its outstanding visible-light-response capability for hydrogen generation from water. However, the low-yield, low practical surface area and high photogenerated charge recombination rate severely limits its photocatalytic performance . Here, in this study high-yield synthesis of g-C 3 N 4 with a large surface area has been achieved successfully through an in situ pyrolysis of cyanamide with the assist of the bifunctional urea. During the synthesis process, urea may decompose into a lot of ammonia and carbon dioxide, which acts as the supplementary-nitrogen-source and bubble-generating template respectively. It is found that the surface area and photocatalytic activity can be controlled by adjusting the addition of the environmentally friendly bifunctional urea. The as-prepared g-C 3 N 4 exhibits unique optical activity as well as photoelectriochemical activity for solar-to-chemical conversion, and this simple bifunctional method may open a new pathway for designing and optimizing of photocatalysts. [ABSTRACT FROM AUTHOR]

Metallic nickel nanoparticles well dispersed in graphitized carbon matrix (Ni@C) by pyrolysis of metal-organic frameworks and leaching treatment of hydrochloric acid could greatly enhance the photocatalytic activity of g-C 3 N 4 under visible light irradiation. For 2.0 wt% Ni@C/g-C 3 N 4 , the average hydrogen evolution rate is 2.15 mmol h −1 g −1 , which is around 88 times higher than that of pure g-C 3 N 4 , and even better than that of platinum-loaded g-C 3 N 4 . The remarkably improved photocatalytic activities through loading Ni@C can be attributed to the cooperative work of Ni nanoparticles and graphene layers, which facilitate the separation of photo-generated carriers and suppress the recombination of the electron-hole pairs. In addition, the hollow onion-like structure can restrain the formation of Ni-hydrogen bonds which modulates desorption of hydrogen. Our studies may open up a promising strategy to design economical noble-metal-free co-catalysts for efficient solar energy conversion. [ABSTRACT FROM AUTHOR]

The mechanism study of redox mediator to transfer the photogenerated electrons is extremely desirable for artificial Z-scheme photocatalytic systems. Here we find that the α-Fe 2 O 3 exposed by {012} and {104} facets can facilitate the reduction of IO 3 − , which results in increasing the activity of photocatalytic water oxidation significantly. By employing NaIO 3 as an electron acceptor, the O 2 evolution activity (309.4 μmol h −1 g −1 ) of α-Fe 2 O 3 photocatalyst mainly exposed by {012} and {104} facets is 84 times higher than that (3.68 μmol h −1 g −1 ) of α-Fe 2 O 3 mostly exposed by {101} and {111} planes. We anticipate that the findings in this work may open the door for further development of enhanced Z-scheme photocatalytic systems. [ABSTRACT FROM AUTHOR]

The search of efficient and stable photocatalysts for the evolution of hydrogen from water using solar energy is of great importance for material science today. Limited by the relatively inferior stability of oxynitrides, the availability of these visible-light-response materials in photocatalysis is still far below what is expected. Here we report a novel oxynitride Ce 0.3 Zr 0.7 O 1.88 N 0.12 as an efficient and stable H 2 -evolving photocatalyst under visible light irradiation, which can further enable overall water splitting by coupling with an O 2 -evolving photocatalyst via Z-scheme. Experimental and theoretical results together reveal that the origin of the excellent activity and stability of Ce 0.3 Zr 0.7 O 1.88 N 0.12 photocatalyst can be attributed to the improved separation rate of photoexcited charge carriers by surface and sub-surface oxygen vacancies. The present study provides a strategy to engineer efficient and stable photocatalysts, and the oxynitride mentioned above could act as a promising candidate of H 2 -evolving photocatalyst for designing a prominent Z-scheme photocatalytic system. [ABSTRACT FROM AUTHOR]

Cadmiun sulfide (CdS) is considered as a promising semiconductor photocatalyst for its outstanding light absorbance and photoinduced charge separation, but it suffers from severe photocorrosion, mainly due to the sluggish kinetics of holes transfer. In this work, we introduce the strong local Coulomb attraction, which is demonstrated via the in situ K-edge X-ray absorption near edge (XANES) analysis, to accelerate the migration of holes for long-term photocatalytic activity. As a proof-of-concept sample, the hole-attraction Fe 2 O 3 /CdS nanorods evidence an outstanding stability of at least 6 days without obvious deactivation, and feature with an excellent H 2 evolution rate of 20.7 mmol g −1 h −1 . Moreover, this Coulomb attraction strategy can be leveraged to enhance the photocatalytic performance of Zn 0.5 Cd 0.5 S, indicating the wide application of the strategy. [ABSTRACT FROM AUTHOR]

The development of low-Pt catalysts is important for the large-scale application of Pt-based catalysts. Catalytic reactions mainly occur on the surface or interface of a material, and thus the surface properties of the catalyst will strongly affect their catalytic activity; this phenomenon has attracted widespread attention. Here, a series of Pt NPs with different chemical states and particle sizes were obtained by changing the light source wavelength, light time, and other conditions of light deposition synthesis. The Pt-TiO 2 catalyst has excellent potential in both photocatalytic hydrogen evolution (4.5 mmol·g−1·h−1) and electrocatalytic hydrogen evolution (26 mV@10 mA cm−2). We also found that the photocatalytic activity is more sensitive to the chemical state of Pt and that reducing the catalyst size can improve the electrocatalytic activity. This work not only provides a green and effective method to adjust the chemical state of precious metals on metal oxides but also helps to understand the impact of surface states on the catalytic process. A series of Pt NPs with different chemical states and sizes were embedded in TiO 2 (B) via a modified photochemical reduction method. The optimized Pt-TiO 2 (B) bifunctional catalyst exhibited excellent p-HER and e-HER catalytic activity. [Display omitted] • A series of Pt NPs with different chemical states and particle sizes were obtained by a photochemical strategy. • The optimized Pt-TiO 2 catalyst has excellent potential in both p-HER (4.5 mmol g−1 h−1) and e-HER (26 mV@10 mA cm−2). • The p-HER is more sensitive to the chemical state of Pt, and reducing the catalyst size improves the e-HER. • This work provides a new idea to promote catalytic activity by adjusting the catalyst's state and size. [ABSTRACT FROM AUTHOR]

• The carboxyl group with electron-withdrawing effect was grafted on the surface of graphite carbon nitride. • The electron-withdrawing effect can promote the separation and migration of carriers to improve photocatalytic performance. • The performance achieved 52 times enhancement with an apparent quantum yield of 15.7 % at 420 nm. Graphitic carbon nitride (g-C 3 N 4) has recently emerged as a promising candidate for photocatalytic hydrogen evolution, but only showed limited activity owing to its sluggish photogenerated carriers separation and migration. Herein, the carboxyl-functionalized g-C 3 N 4 (O CN) was synthesized by a grafting post-treatment method to alleviate the negative influences from this intrinsic drawback. As a result, the surface carboxyl groups greatly improve charge carrier dynamics to suppress carriers recombination via the driving force originated from its electron-withdrawing effects. The resultant O CN exhibits 52 times higher hydrogen evolution rate than the pristine, and possesses a high apparent quantum yield (AQY) of 15.7 % at 420 ± 15 nm. This work deepens the understanding of the surface group related modifications for photocatalytic materials, further providing a promising approach for rational design of photocatalysts with highly efficient solar energy conversion. [ABSTRACT FROM AUTHOR]