Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red-light irradiation for tungsten nitride. This work represents the first red-light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization.

Exfoliation of bulk graphitic carbon nitride (BCN) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic performance. Compared with BCN, the 2D g-C 3 N 4 nanosheets (CNNS) have larger specific surface areas and more reaction sites. With the etching assistance of anhydrous ethylenediamine, BCN can be successfully peeled off into 2D CNNS with a large lateral size of more than 15 μm which is much larger than that of other works. After appropriate etch by anhydrous ethylenediamine, the specific surface area of g-C 3 N 4 expands from 4.7 to 31.1 m 2 g −1 and the photocatalytic hydrogen evolution rate increases 7.4 times, from 4.8 to 35.3 μmol h −1 . In contrast to other reported methods, the strategy to fabricate 2D CNNS in this work is convenient and it is the first time to report the fabrication of 2D CNNS with the assistance of alkaline reagent.

Hydrogen bonding (H-bond) interactions have been regarded as a topic of vital scientific research in areas ranging from inorganic to biological chemistry. However, the application and elucidation of surface H-bond functionalized photocatalysts and the alteration of the character of the photocatalyst itself have not been paid sufficient attention. Here we show the high efficiency of visible-light-driven photocatalytic H 2 production, achieved by using a surface H-bonding network decorated g-C 3 N 4 photocatalyst. The hydrated g-C 3 N 4 was designed and synthesized by a facile surface treatment in a slightly alkaline environment. According to NMR and theoretical modeling, the H-bonding bridge can effectively shorten the distance between water molecules and g-C 3 N 4 , provide multiple channels for the transition between protons and the excited electrons on g-C 3 N 4 , stabilize the anionic intermediate and transition states, and restrain charge recombination. The present result opens new opportunities towards a potential approach to designing a new generation of photocatalyst systems.

The atomically controlled transition of nanohybrids and their effects on charge-carrier dynamics are highly desirable for fundamental studies in photocatalysis. Herein, for the first time, a method combining atomic monodispersity and single-atom alloy was used to prepare a new form of highly efficient silver-based cocatalysts (Ag & PtAg) on graphitic carbon nitride, representing a novel photocatalytic system for hydrogen evolution.