Interfacial Engineering for Improved Photocatalysis in a Charge Storing 2D Carbon Nitride: Melamine Functionalized Poly(heptazine imide)

Abstract

Carbon nitrides constitute a class of earth‐abundant polymeric semiconductors, which have high potential for tunability on a molecular level, despite their high chemical and thermal inertness. Here the first postsynthetic modification of the 2D carbon nitride poly(heptazine imide) (PHI) is reported, which is decorated with terminal melamine (Mel) moieties by a functional group interconversion. The covalent attachment of this group is verified based with a suite of spectroscopic and microscopic techniques supported by quantum–chemical calculations. Using triethanolamine as a sacrificial electron donor, Mel‐PHI outperforms most other carbon nitrides in terms of hydrogen evolution rate (5570 µmol h−1 g−1), while maintaining the intrinsic light storing properties of PHI. The origin of the observed superior photocatalytic performance is traced back to a modified surface electronic structure and enhanced interfacial interactions with the amphiphile triethanolamine, which imparts improved colloidal stability to the catalyst particles especially in contrast to methanol used as donor. However, this high activity can be limited by oxidation products of donor reversibly building up at the surface, thus blocking active centers. The findings lay out the importance of surface functionalization to engineer the catalyst–solution interface, an underappreciated tuning parameter in photocatalytic reaction design.

Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

“…[ 44 ] These were fitted by a combination of an exponential and a Γ‐function (Figure 4c and Figure S50, Supporting Information). [ 10 ] A priori, both recombination types can show a distribution decay nature according to a Γ function. [ 45 ] However, the best fit obtained in all cases is an exponential function attributed to the faster decay in the bulk (<0.54 ns).…”

“…In particular, surface terminations were recently described to have a significant impact on the photocatalytic behavior of PHI by enhancing its interaction with reactants. [ 10 ]…”

2D Metal‐Free Nanomaterials Beyond Graphene and Its Analogues toward Electrocatalysis Applications

“…The functionalization strategies, which mainly include heteroatoms doping, graft of functional groups, and defects creation, are highly desirable to activate the intriguing physicochemical properties including but not limited to conductivity improvement, thereby accelerating the catalytic reaction kinetics of g-C 3 N 4 -based electrocatalysts. [68][69][70][71] Doping heteroatoms (e.g., P, B, S, I, etc.) into g-C 3 N 4 is an effective approach for tuning the electronic structures and bandgap configurations, which would promote the electrocatalytic activity accordingly.…”

Conductivity mechanism in ionic 2D carbon nitrides: from hydrated ion motion to enhanced photocatalysis

“…However, the relative PL intensity is not a suitable measure for the photocatalytic performance due to the overall low PL quantum yields observed for PHI. Time-resolved PL measurements, excited at a wavelength of 370 nm, were fitted by an exponential decay function and a Γ distribution (Figure S64, Supporting information) [67,68] highlighting at least two different decay processes being present on the probed time scales in the material. The shorter lifetime (τexp) of ~110 ps up to ~290 ps corresponds to an internal recombination of charge carriers in the bulk of PHI, whereas the longer lifetime (τmode) of ~200 ps to 840 ps is likely caused by decay processes on the surface (Table S18, Supporting information).…”