Improved Plasmonic Hot-Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad-Spectrum Photocatalytic H2 Evolution.

Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a "holy grail" for researchers, but is still a challenging issue. Herein, based on the common polymeric carbon nitride (PCN), a hybrid co-catalysts system comprising plasmonic Au nanoparticles (NPs) and atomically dispersed Pt single atoms (PtSAs) with different functions was constructed to address this challenge. For the dual co-catalysts decorated PCN (PtSAs-Au2.5/PCN), the PCN is photoexcited to generate electrons under UV and short-wavelength visible light, and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H2 evolution. Furthermore, the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance, and the adjacent PtSAs trap the plasmonic hot-electrons for H2 evolution via direct electron transfer effect. Consequently, the PtSAs-Au2.5/PCN exhibits excellent broad-spectrum photocatalytic H2 evolution activity with the H2 evolution rate of 8.8 mmol g-1 h-1 at 420 nm and 264 µmol g-1 h-1 at 550 nm, much higher than that of Au2.5/PCN and PtSAs-PCN, respectively. This work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.

N-hexane-assisted synthesis of plasmonic Au-mediated polymeric carbon nitride photocatalyst for remarkable H2 evolution under visible-light irradiation.

Plasmonic Au-mediated polymeric carbon nitride (PCN) has been recognized as one of the promising materials for photocatalytic applications due to its excellent properties in wide visible light spectrum, however it is still hindered by low catalytic efficiency. In this work, it was established that strong metal-support interactions (MSI) at the interface between plasmonic Au nanoparticles (NPs) and PCN nanosheets (PCNS) improves its photocatalytic efficiency. The resulting Au/PCNS2.5 exhibits excellent photocatalytic activity with H2 evolution rate up to 4.84 mmol g-1h-1 under visible light, 12.4 times higher than that of bulk PCN. Such strong MSI significantly strengthens the localized surface plasmon resonance (LSPR) effect of Au NPs and the charge "pump" role of Schottky junctions at Au-PCNS interface, resulting in broad light absorption range as well as effective separation and transfer of charge carrier. This work provides a new way to design the plasmonic photocatalysts for splitting water as well as other plasmon-driven chemical reactions.

Linking melem with conjugated Schiff-base bonds to boost photocatalytic efficiency of carbon nitride for overall water splitting.

Developing an efficient single component photocatalyst for overall water splitting under visible-light irradiation is extremely challenging. Herein, we report a metal-free graphitic carbon nitride (g-CxN4)-based nanosheet photocatalyst (x = 3.2, 3.6, or 3.8) with melem rings conjugated by Schiff-base bonds (N[double bond, length as m-dash]C-C[double bond, length as m-dash]N). The presence of the conjugated Schiff-base bond tunes the band gap of g-CxN4 and, more importantly, serves as an electron sink to suppress electron-hole pair recombination. The projected density of states (PDOS) calculations suggest that the melem ring and Schiff-base bond act as oxidizing and reducing centers, respectively, for photocatalytic water splitting. As a result, g-CxN4, in particular g-C3.6N4, can catalyze overall water splitting without the need for any co-catalyst or sacrificial donor. Under visible light (>420 nm wavelength) irradiation, g-C3.6N4 catalyzes the overall water splitting with H2 and O2 generation rates of 75.0 and 36.3 µmol h-1 g-1, respectively. g-C3.6N4 is the most efficient single-component photocatalyst ever reported for overall water splitting. Our studies demonstrate a new approach for tuning the bandgap and the electronic structure of graphitic carbon nitride for maximizing its photocatalytic performance for water splitting, which will be important for hydrogen generation and for energy applications.

Ni nanoparticles supported on graphitic carbon nitride as visible light catalysts for hydrolytic dehydrogenation of ammonia borane.

The development of a robust and low-cost non-noble metal catalyst for photocatalytic H2 evolution is of great importance for practical applications. In this study, monodisperse Ni nanoparticles of controlled sizes were prepared by a facile method and anchored on graphitic carbon nitride (g-C3N4) nanosheets via a self-assembly route. The noble-metal-free Ni/g-C3N4 composite catalysts exhibit excellent photocatalytic activities for the hydrolytic dehydrogenation of ammonia borane (AB) under visible light. An optimum AB hydrolysis rate was obtained when the size of the Ni NPs was 3.2 nm, with an initial turnover frequency of 18.7 mol(hydrogen) mol(catalyst)-1 min-1 and an apparent activation energy of 36 kJ mol-1. This study provides validity for constructing high performance first-row transition metal nano-photocatalysts for the hydrolytic dehydrogenation of AB.

High-density defects on PdAg nanowire networks as catalytic hot spots for efficient dehydrogenation of formic acid and reduction of nitrate.

Controlling the surface defects of nanocrystals is a new way of tuning/boosting their catalytic properties. Herein, we report networked PdAg nanowires (NWs) with high-density defects as catalytic hot spots for efficient catalytic dehydrogenation of formic acid (FA) and catalytic reduction of nitrates. The networked PdAg NWs exhibit composition-dependent catalytic activity for the dehydrogenation reaction of FA without any additive, with Pd5Ag5 NWs exhibiting the highest activity. They also show good durability, reflected by the retention of their initial activity during the dehydrogenation reaction of FA even after five cycles. Their initial TOF is 419 h-1 at 60 °C in water solution, much higher than those of the most Pd-based catalysts with a support. Moreover, they can efficiently reduce nitrates to alleviate nitrate pollution in water (conversion yield >99%). This strategy opens up a new green synthetic technique to design support-free heterogeneous catalysts with high-density defects as catalytic hot spots for efficient dehydrogenation catalysis of FA to meet the requirement of fuel cell applications and catalytic reduction of nitrates in water polluted with nitrates.