Chlorophyll‐Based Organic Heterojunction on Ti₃C₂T_x MXene Nanosheets for Efficient Hydrogen Production

Abstract

The Z‐scheme process is a photoinduced electron‐transfer pathway in natural oxygenic photosynthesis involving electron transport from photosystem II (PSII) to photosystem I (PSI). Inspired by the interesting Z‐scheme process, herein a photocatalytic hydrogen evolution reaction (HER) employing chlorophyll (Chl) derivatives, Chl‐1 and Chl‐2, on the surface of Ti3C2Tx MXene with two‐dimensional accordion‐like morphology, forming Chl‐1@Chl‐2@Ti3C2Tx composite, is demonstrated. Due to the frontier molecular orbital energy alignments of Chl‐1 and Chl‐2, sublayer Chl‐1 is a simulation of PSI, whereas upper layer Chl‐2 is equivalent to PSII, and the resultant electron transport can take place from Chl‐2 to Chl‐1. Under the illumination of visible light (>420 nm), the HER performance of Chl‐1@Chl‐2@Ti3C2Tx photocatalyst was found to be as high as 143 μmol h−1 gcat−1, which was substantially higher than that of photocatalysts of either Chl‐1@Ti3C2Tx (20 μmol h−1 g−1) or Chl‐2@Ti3C2Tx (15 μmol h−1 g−1).

Advances and Promises of 2D MXenes as Cocatalysts for Artificial Photosynthesis

“…Many materials such as metal nanoparticles (e.g., Pt, Co, Au, Cu), metallic oxides (e.g., NiO, Ru 2 O, IrO x ), and metal sulfides (e.g., NiS, SnS 2 , MoS 2 ) have been used as cocatalysts in photocatalytic systems. [16,82,83] In recent years, the 2D materials MXenes show huge potential to be used as cocatalysts due to their metal-like conductivity and suitable energy structures. According to the density functional theory (DFT) calculations, the Femi level of Ti 3 C 2 MXene is more positive than that of the CB of most typical semiconductors, indicating that it is possible for the photoelectrons migrating from semiconductors to the MXene.…”

“…The functions of cocatalysts in photocatalytic system are mainly reflected in the following aspects. [15][16][17] First, introducing a cocatalyst with higher work function than that of the semiconductors can facilitate the carrier separation via a charge transfer process from semiconductor to the cocatalyst. Second, the photogenerated carriers could undergo a fast migration to the semiconductor surface in the presence of cocatalysts, resulting in the effective suppression of photocorrosion and therefore improving the stability of the catalytic system.…”

Ultrathin 2D/2D Ti3C2Tx/semiconductor dual-functional photocatalysts for simultaneous imine production and H2 evolution

“…Among various cocatalysts, ultrathin 2D noble-metal-free transition metal carbon/nitride Mxenes (e.g., Ti 3 C 2 T x ) have received widespread attention in the eld of photocatalysis due to their wide light absorption capacity, abundant surface bridging groups and unsaturated active metal centers. [29][30][31] Moreover, the ultrathin 2D Mxenes have proven to be an ideal support to in situ construct 2D/2D heterostructured photocatalysts. [32][33][34] For instance, Huang et al reported the photocatalytic overall water splitting with ultrathin 2D/2D Ti 3 C 2 / BiVO 4 nanosheets with enhanced performance compared to pure BiVO 4 due to the improved charge transfer towards the cocatalyst Ti 3 C 2 .…”

Semi‐Synthetic Chlorophyll‐Carotenoid Dyad for Dye‐Sensitized Photocatalytic Hydrogen Evolution

“…[4][5][6] PHE systems based on various kinds of semiconductors have been extensively investigated so far, [7,8] among which Pt/TiO 2 has been regarded as one of the most major photocatalysts. [9][10][11][12][13] To overcome the inherent defects of TiO 2 such as large band gap which leads to low photocatalytic efficiency, some research groups reported the development of dye-sensitized Pt/TiO 2 photocatalysts for hydrogen evolution. [14][15][16][17] A recent trend for sensitizing Pt/TiO 2 is the use of metal-free organic dyes with strong absorptivity and panchromatic sensitization properties.…”