Search

Considerable efforts have been made to enhance the hydrogen evolution reaction (HER) catalytic performance of Janus MoSSe monolayer, which have been considered to be a promising candidate due to the unique asymmetry structure. However, the activation effect remains non-optimal for the inert Janus MoSSe basal plane at present. Herein, a train of transition metal (TM) atoms were anchored on the S-/Se-/Mo-defective MoSSe basal plane to screen effective TM single-atom catalysts for HER through density functional theory (DFT) computations. Interestingly, the single Co atom anchored on Mo-defective MoSSe and the single Zn or Cd atom anchored on S-defective MoSSe were judged to possess excellent HER performance yielding a near-zero ΔGH (ΔGH = −0.050, −0.095, −0.098 eV, respectively), which is comparable to the optimized Pt-SACs. The enhanced HER activity is attributed to the doping of TM atoms (Co, Zn and Cd) which improves the conductivity of the original MoSSe and offers unoccupied states near the Fermi level decreasing the energy barrier of electrons transfer between H and TMs@MoSSe surface. In addition, the change of unoccupied antibonding states of active atoms leads to appropriate interaction between the active sites and H. The hybridization between H-s orbital and the TMs@MoSSe systems around the Fermi level also suggests the formation of stable bonding-antibonding hydrogen adsorption states. This work reveals an effective way of activating MoSSe basal plane for HER.

Herein, we developed a facile approach to fabricate oxygen vacancies-mediated TiO2 (OVs-TiO2) nanocrystals via an intrinsic carbon-doping induced strategy. The intrinsic carbon-doped TiO2 nanocrystals were firstly synthesized by water-controlled-releasing solvothermal (WCRS) process using ethanol, acetic acid and titanium tetraisopropoxide (TTIP) as precursors. The carbon-doped TiO2 was calcined at 325 °C under N2 atmosphere to introduce the OVs. The obtained OVs-TiO2 displayed outstanding photocatalytic NO removal performance under visible light irradiation (λ˃510 nm), in comparison with the commercial P25. With the aid of DFT calculations, we revealed that the intrinsic carbon-doping was beneficial for the formations of OVs in carbon-doped TiO2. Moreover, the OVs played crucial roles in improving light absorption, facilitating charge separation, and activating surface reactions to enhance the photocatalytic NO removal performance.

The insufficient oxidation capacity, high carrier recombination rate and limited sunlight absorption seriously suppress the photocatalytic activity of pure g-C3N4. Using state-of-the-art hybrid density functional theory, we report an efficient method to tackle all aforementioned issues of g-C3N4 by metal-nonmetal (S and K) co-doping here. We find the adsorption of K atom on hollow site causes dynamic strain of g-C3N4. The S + K co-doping not only shifts the band edges downwards to achieve a much large overpotential of ca. 0.76 V, but also significantly extends the visible-light absorption threshold of g-C3N4. More importantly, the newly established channel between neighboring heptazine units in the doped structure is highly favorable for the separation of charge carriers. Our results help the design of high-performance visible-light-responsive g–C3N4–based photocatalyst for solar water splitting.

Recently, 2D ferromagnets have emerged as a hot research topic, especially after the exfoliation of monolayer ferromagnetic Fe3GeTe2 from its bulk structure (Nature 2018, 563, 94; Nat. Mater. 2018, 17, 778). In this work, we systematically report the adsorption behavior of CO, CO2, H2, H2O, NO, and O2 on the pristine and Te-deficient Fe3GeTe2 (FGT and d-FGT) monolayer using hybrid density functional theory. We find that the toxic gas molecules (CO and NO) and O2 molecular are chemically anchored at the surface of the pristine FGT, while the H2O, CO2, and H2 are physically associated with FGT. Interestingly, the introduction of Te deficiency would significantly enhance the covalent interactions between the substrate and the gas molecules, especially for CO2 and H2O, whose adsorption type has evolved from physisorption to chemisorption. Furthermore, the adsorption capacity of (d-)FGT to gas molecules is found to be stronger than that of the two well-studied 2D materials: MoS2 and MXenes. Meanwhile, the adsorption changes the electronic structure of (d-)FGT but does not change the metallicity of FGT. This work provides a valuable reference for the application of 2D metallic ferromagnetic materials in the field of catalysis, sensors, gas storage, and environmental remediation.