Highly efficient composite photocatalysts composed of silver cyanamide (Ag2NCN) and anatase titania (TiO2) were fabricated through a chemical precipitation process of silver nitrate and cyanamide in TiO2 suspensions. The TiO2 nanoparticles around 15 nm were immobilized on the surface of rectangular Ag2NCN particles to form a hetero-structure, and the contents of TiO2 were varied to tune the structure and the photocatalytic performances. In comparison with single TiO2 or Ag2NCN, the TiO2/Ag2NCN nanocomposites exhibited a prominent improved photocatalytic activity in the hydrogen generation, and the hydrogen evolution rate (1494.0 μmol (g h)−1) was higher than most of the reported TiO2-composite photocatalysts. Based on the structure investigation, the photocatalytic mechanism of these TiO2/Ag2NCN nanocomposites was proposed. The enhanced photocatalytic activity was attributed to three points: the matched energy level between TiO2 and Ag2NCN promoted the electron–hole transfer and thus inhibited the recombination of photogenerated electrons and holes; the great electron storage capacity of metallic silver produced in the photocatalytic process also facilitated the charge separation; in addition, the expanded absorption spectrum because of the composite structure enhanced the UV and visible light response ability. These TiO2/Ag2NCN nanocomposites also presented good photocatalytic stability in the typical cycle tests. This work provided new insights into fabricating highly efficient composite photocatalysts containing silver and TiO2 for hydrogen generation.
Metal cyanamides have an organic–inorganic hybrid structure similar to MOFs, which are expected to possess interesting catalytic properties. However, the structural complexity of these compounds sets up a big barrier to realize shape manipulation and further understanding on the structure–activity relationship. Here, we describe seed-mediated colloidal synthesis as a facile approach to obtain Ag2NCN near-monodisperse nanocrystals (NCs: nanorods, nanowires, and nanosheets) and their related CO2 catalytic activity. The control experiment unveiled the prominent role of the anisotropy for quasi-linear [NCN]2– anions in obtaining the desired growth order of different crystal planes. The formic acid production of nearly 20% Faradaic efficiency is observed when the as-prepared Ag2NCN NCs were tested for electrocatalytic CO2 reduction reactions. The exposed (200) planes exhibit evident higher catalytic activity compared to other planes, showing morphology-dependent activity. Our result reveals that the anisotropic structure of ions leads to their preferential growth of the NCs and thus may have greater implications for the shape-controlled synthesis of complex ions containing compounds and their related catalytic activity.
A new hybrid membrane composed of poly(vinylidene fluoride) (PVDF) and silver cyanamide (Ag2NCN) has been successfully fabricated via an induced phase inversion method by blending Ag2NCN particles and PVDF casting solution. The rectangular Ag2NCN particles were well dispersed in PVDF membranes via weak physical interaction, and the Ag2NCN amount was varied to investigate the effect of the Ag2NCN particles on the photocatalytic properties of PVDF/Ag2NCN hybrid membranes. The as-prepared hybrid membranes display excellent photocatalytic activity towards the degradation of Acid Blue 1 under visible light irradiation, showing great potential for practical applications. Particularly, these PVDF/Ag2NCN hybrid membranes have enhanced photocatalytic properties under acidic conditions, and a possible H+-promoted photocatalytic mechanism was proposed in this study. Furthermore, this facile and generic strategy may provide a convenient and powerful method to fabricate other polymer–inorganic hybrid membranes for advanced applications.
As photocatalysts, heterojunction materials have attracted much attention because of their capacity to integrate the promising performance of the individual components. Here, a series of heterojunction materials composed of silver cyanamide (Ag2NCN) and graphitic carbon nitride (g-C3N4) have been fabricated using a facile grinding method. Upon photoexcitation, the heterojunction materials exhibited enhanced photocatalytic activity in the hydrogen evolution reaction (322.35 μmol g−1 h−1), 82.87 and 117.65 times higher than that of the pristine Ag2NCN and g-C3N4, respectively. The photoelectrochemistry results revealed that the loading of Ag2NCN onto g-C3N4 could be favorable to the photogenerated charge separation and transfer in the heterojuction system. In addition, the spent heterojuction retained a better photocatalytic activity after 30 hours recycling. Furthermore, the excellent synergetic effect between Ag2NCN and g-C3N4 could achieve the effectively promoted separation of photogenerated electron–hole pairs, thus leading to the enhancement of photocatalytic performance under simulated sunlight illumination. This work could provide a general strategy to fabricate Ag-based materials on g-C3N4 photocatalysts with superior H2 evolution performance.
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