It is of great importance to explore and achieve a more effective approach toward the controllable synthesis of singleatom-based photocatalysts with high metal content and long-term durability. Herein, single-atom platinum (Pt) with high loading content anchored on the pore walls of two-dimensional βketoenamine-linked covalent organic frameworks (TpPa-1-COF) is presented. Aided by advanced characterization techniques of aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, it has been demonstrated that atomically dispersed Pt is formed on the TpPa-1-COF support through a six-coordinated C 3 N−Pt−Cl 2 species. The optimized Pt 1 @TpPa-1 catalyst exhibits a high photocatalytic H 2 evolution rate of 719 μmol g −1 h −1 under visible-light irradiation, a high actual Pt loading content of 0.72 wt %, and a large turnover frequency (TOF) of 19.5 h −1 , with activity equivalent to 3.9 and 48 times higher than those of Pt nanoparticles/TpPa-1 and bare TpPa-1, respectively. The improved photocatalytic performance for H 2 evolution is ascribed to the effective photogenerated charge separation and migration and well-dispersed active sites of single-atom Pt. Moreover, density functional theory (DFT) calculations further reveal the role of Pt single atoms in the enhanced photocatalytic activity for H 2 evolution. Overall, this work provides some inspiration for designing single-atom-based photocatalysts with outstanding stability and efficiency using COFs as the support.
Synergistic
nitrogen reduction and water oxidation process is significant
to the photocatalytic fixation of nitrogen. However, the coupling
mechanism remains ambiguous and lacks study. Herein, we report enhanced
photocatalytic nitrogen fixation on single-atom Fe-modified macro-/mesoporous
TiO2-SiO2 (Fe-T-S), with a high ammonia generation
rate of 32 μmol g–1 h–1 without
any sacrificial agent and cocatalysts. Experimental and theoretic
calculation studies confirmed the formation of a photoinduced hole-trapping
polaron on the Fe dopant, resulting in the high-valent Fe(IV) species.
The single-atom Fe(IV) site is responsible for water oxidation and
helps promote N2 hydrogenation on neighboring oxygen vacancy.
This study explicitly unravels the key to achieve the coupling between
photocatalytic N2 hydrogenation and water oxidation through
a doping strategy and provides significant guidance for the rational
design of photocatalysts for ammonia synthesis.
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