Enhanced Photocatalytic Water Splitting in a C₂N Monolayer by C‐Site Isoelectronic Substitution

Abstract

Two-dimensional (2D) semiconductors have shown great promise as efficient photocatalysts for water splitting. Tailoring the band gap and band edge positions are the most crucial steps to further improve the photocatalytic activity of 2D materials. Here, we report an improved photocatalytic water splitting activity in a C N monolayer by isoelectronic substitutions at the C-site, based on density functional calculations. Our optical calculations show that the isoelectronic substitutions significantly reduce the band gap of the C N monolayer and thus strongly enhance the absorption of visible light, which is consistent with the observed redshift in the optical absorption spectra. Based on the HSE06 functional, the calculated band edge positions of C Si N and C Ge N monolayers are even more favorable than the pristine C N monolayer for the overall photocatalytic activity. On the other hand, for the C Sn N monolayer, the conduction band minima is more positive than the oxygen reduction potential and, hence, Sn substitution in C N is unfavorable for the water decomposition reaction. In addition, the isoelectronic substitutions improve the separation of e -h pairs, which, in turn, suppress the recombination rate, thereby leading to enhanced photocatalytic activity in this material. Our results imply that Si-, and Ge-substituted C N monolayers will be a promising visible-light photocatalysts for water splitting.

Band Engineering of Carbon Nitride Monolayers by N-Type, P-Type, and Isoelectronic Doping for Photocatalytic Applications

“…The lattice parameters of the PBE relaxed C2N unit cell were determined to be a=8.263Å and γ=60 o , which is in good agreement with previous simulations and experimental data. 37,52,59 The lattice parameters of the PBE relaxed C3N unit cell were determined to be a=4.861Å and γ=120 o , which is also in good agreement with previous results. 38,60 The lattice parameters of the PBE relaxed tg-C3N4…”

Two-Dimensional CdX/C2N (X = S, Se) Heterostructures as Potential Photocatalysts for Water Splitting: A DFT Study

“…The calculated in-plane bond lengths (C–C = 1.429/1.468 Å; C–N = 1.336 Å) are in good agreement with reported values. 32 , 33 2 × 2 supercells of CdS and CdSe monolayers are illustrated in Figure 1 b,c. CdS and CdSe monolayers were cleaved out from the (0001) plane of the wurtzite phase of CdS and CdSe, respectively.…”

Rational design of C2N-based type-II heterojunctions for overall photocatalytic water splitting

“…† The C 2 N monolayer exhibits a direct band gap of 2.49 eV at the G point of the Brillouin zone, which agrees well with those in previous reports. 23,46 The MX monolayers (GaSe, GaTe and InTe) exhibit indirect band gaps of 2.97, 2.21 and 2.21 eV, respectively. For GaSe and InTe monolayers, the CBM is at the G point while the VBM is located between the G and K points.…”