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We present the rational design of carbon/potassium poly(heptazine imide) (KPHI) heterostructures via one-step salt-melt assisted condensation for efficient photocatalysis. Hybridizing KPHI with an adenine-derived carbonaceous material (Ad-carbon) displayed an outstanding photocatalytic H2 evolution activity (738 μmol h−1 gcat−1; with 3 wt% Pt as the cocatalyst) and photocatalytic H2O2 production (3.94 mmol h−1 gcat−1). We establish that the Ad-carbon simultaneously operates as an electron acceptor and a photosensitizer based on structural, optical and photo(electro)chemical characterization. Building an intimate heterojunction between the Ad-carbon and KPHI induced spatial charge separation and prolonged the carrier lifetime. From electrocatalysis, we confirmed that coupling Ad-carbon with KPHI enhanced the surface reaction kinetics towards H2 evolution and O2 reduction reactions. Moreover, visual evidence of superior charge transport in the hybrid photocatalyst is revealed through the photodeposition of smaller Pt nanoparticles (∼7 nm) with uniform distribution on the carbon regions, which also accounts for the increased catalytic activity. [ABSTRACT FROM AUTHOR]

Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H2). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure–activity correlations to enhance the photoefficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defect-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reaction (HER). The CN(T)-7-NP nano-heterostructure comprising Au nanoparticles (NPs) of ∼7 nm and thiourea-derived defective CN, exhibits an excellent H2 production rate of 76.8 μmol g−1 h−1 from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible light absorption and interfacial charge separation. The surface ligands used to control Au nanostructure morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au–CN interfacial sites in these nanocomposites facilitate the separation of e−/h+ pairs after light excitation and provide lower energy barrier pathways for H2 production by photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

Ammonia has a large volume energy density and consequently high potential for application as a fuel and energy reservoir in the future. In this study, the dinuclear FeIII metallacycle complex [Fe2(H2opba)2Cl2(dmso)2]·2CH2Cl2·2dmso (1) with excellent capacity to selectively adsorb ammonia (11.3 mmol g−1) was investigated, demonstrating a strong preference for nitrogenous compounds, especially short-chain amines. The adsorption results suggest that the cavity in the structure of 1 has an essential role in the adsorption mechanism i.e. it is the responsible for size selectivity of 1 during the adsorption process. To better understand the adsorption mechanism of ammonia, 1 was fully characterized before and after adsorption. Thermogravimetric-mass spectrometry (TG-MS) and ammonia isotherm experiments revealed that 8 ammonia molecules were physisorbed by the complex cavity (free ammonia) and 4 ammonia molecules were chemisorbed (coordinated ammonia) per dinuclear metallacycle unit. Further characterization also confirmed the proposed adsorption mechanism, corroborating the structural modification of the compound after its interaction with ammonia; in addition, reuse tests showed that despite a small loss of efficiency, the compound was capable of desorbing most of the ammonia and could be used consecutively for at least three cycles. Thus, 1 is a potential ammonia storage material and adsorbent for the removal of ammonia from effluents. [ABSTRACT FROM AUTHOR]