Photocatalytic Water Splitting Reaction Catalyzed by Ion-Exchanged Salts of Potassium Poly(heptazine imide) 2D Materials

Abstract

Potassium poly (heptazine imide) (K-PHI), a crystalline two-dimensional carbon–nitride material, is an active photocatalyst for water splitting. The potassium ions in K-PHI can be exchanged with other ions to change the properties of the material and eventually to design the catalysts. We report here the electronic structures of several ion-exchanged salts of K-PHI (K, H, Au, Ru, and Mg) and their feasibility as water splitting photocatalysts, which were determined by density functional theory (DFT) calculations. The DFT results are complemented by experiments where the performances in the photocatalytic hydrogen evolution reaction (HER) were recorded. We show that due to its narrow band gap, Ru-PHI is not a suitable photocatalyst. The water oxidation potentials are straddled between the band edge potentials of H-PHI, Au-PHI, and Mg-PHI; thus, these are active photocatalysts for both the oxygen and hydrogen evolution reactions, whereas K-PHI is active only for the HER. The experimental data show that these are active HER photocatalysts, in agreement with the DFT results. Furthermore, Mg-PHI has shown remarkable performance in the HER, with a rate of 539 μmol/(h·g) and a quantum efficiency of 7.14% at 410 nm light irradiation, which could be due to activation of the water molecule upon adsorption, as predicted by our DFT calculations.

Gradient Zn-Doped Poly Heptazine Imides Integrated with a van der Waals Homojunction Boosting Visible Light-Driven Water Oxidation Activities

“…This result suggests that the Zn 2+ ions are coupled with edge nitrogen atoms of two adjacent heptazine rings, which accords well with the ATR−FTIR results. 37,51,52 These results further demonstrate the presence of the Zn-PHI/PHI VDW homojunction in the Zn 0.2 -PHI/PHI catalyst materials.…”

“…In comparison with the PCN catalyst, obvious changes in both peak shifts and intensities of C i and C e of PHI could be observed, which is probably ascribed to the structure transformation from 1D chains of melon with an abundance of terminal amino groups (Figure S7b,d) to 2D PHI-based planes with a fully condensed structure. − Interestingly, in comparison to pristine PHI, the Zn 0.2 -PHI/PHI catalysts exhibit two new chemical shift peaks located at 155 and 163 ppm, which are ascribed to the C ii atoms and C ee species of the Zn-modified heptazine heterocycle, respectively. This result suggests that the Zn 2+ ions are coupled with edge nitrogen atoms of two adjacent heptazine rings, which accords well with the ATR–FTIR results. ,, These results further demonstrate the presence of the Zn-PHI/PHI VDW homojunction in the Zn 0.2 -PHI/PHI catalyst materials.…”

Water on porous, nitrogen-containing layered carbon materials: the performance of computational model chemistries

“…Both M-PHI and H-PHI are semiconductors with respective experimental, optical band gaps of 2.90 eV for H-PHI and 2.68 eV for K-PHI, for example. 17 3. Finally, we consider a C/N-based 2DM of composition C 2 N, derived from hexaazatriphenyle-hexacarbonitrile (HAT-CN).…”

“…The method makes use of Nørskov's model of the normal hydrogen electrode (NHE), accounts for finite pH (through the term DpH) and voltage, U, in an electrochemical setup. It can be used to calculate the overpotential for electrochemical, anodic OER 16,17,62,63 but is also applied to estimate the energetics of photoinduced OER. There a photogenerated exciton takes the role of ''providing the voltage'', U.…”

Photocharging of Semiconductor Materials: Database, Quantitative Data Analysis, and Application in Organic Synthesis

“…[39] Sahoo et al modeled structures of several metal poly(heptazine imide)s and found that in K-PHI and Mg-PHI cations are in the pores between the layers, while in Au-PHI and Ru-PHI cations are in the same plane with PHI layer. [40] Using X-ray absorption spectroscopy data, da Silva et al found that in Fe-PHI, metal cations are in the pores between the layers coordinated by 4 nitrogen atoms-two from each neighboring layer. [41] The structure of cyanamide-functionalized heptazine-based polymer (NCN-CNx, Figure 3c) is represented by zigzag-like strands of heptazine units.…”