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Confined metal clusters as sub-nanometer reactors for electrocatalytic N2 reduction reaction (eNRR) have received increasing attention due to the unique metal-metal interaction and higher activity than single-atom catalysts. Herein, the inspiration of the superior capacitance and unique microenvironment with regular surface cavities of the porous boron nitride (p-BN) nanosheets, we systematically studied the catalytic activity for NRR of transition-metal single-clusters in the triplet form (V3, Fe3, Mo3 and W3) confined in the surface cavities of the p-BN sheets by spin-polarized density functional theory (DFT) calculations. After a two-step screening strategy, Mo3@p-BN was found to have high catalytic activity and selectivity with a rather low limiting potential (–0.34 V) for the NRR. The anchored Mo3 single-cluster can be stably embedded on the surface cavities of the substrate preventing the diffusion of the active Mo atoms. More importantly, the Mo atoms in the Mo3 single-cluster would act as “cache” to accelerate electron transfer between active metal centers and nitrogen-containing intermediates via the intimate Mo-Mo interactions. The cooperation of Mo atoms can also provide a large number of occupied and unoccupied d orbitals to make the "donation–backdonation" mechanism more effective. This work not only provides a quite promising electrocatalyst for NRR, but also brings new insights into the rational design of triple-atom NRR catalysts.

The pristine carbon nitride derived from the thermally-induced polymerization of nitrogen-containing precursors (e.g. cyanamide, dicyanamide, melamine and urea) displays low crystallinity because of the predominantly kinetic hindrance. Herein, we reported a modified molten-salts method to fabricate the crystalline carbon nitride under ambient pressure, which is expected to the large-scale production of crystalline carbon nitride. The obtained crystalline carbon nitride displayed about 3.0 times higher photocatalytic NO removal performance than that of pristine carbon nitride under visible light irradiation (λ

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 vital role of the spin polarization in the electrocatalytic N2 reduction reaction (eNRR) stimulates us to explore the potential of the newly discovered two-dimensional (2D) vdW ferromagnetic materials as NRR electrocatalysts. Here, using density functional theory (DFT) computations, we report the first theoretical prediction that the single-layer defective Fe3GeTe2 acts as a 2D ferromagnetic material toward the NRR with outstanding electrocatalytic activity and high selectivity. Notably, all six hydrogenation steps are exothermic and spontaneous. The highly centralized spin-polarization on the exposed Fe4 center in defective Fe3GeTe2 leads to strong backdonation and substantial activation of the NN triple bond. Moreover, the metallic character of the defective Fe3GeTe2 ensures high-speed transport of carriers. This work not only provides a quite promising electrocatalyst for the NRR but also promotes the application of emerging 2D ferromagnets in the field of energy conversion.

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.

Inspired by the recent practical application of two-dimensional (2D) nanomaterials as gas sensors, catalysts, and materials for waste gas disposal, herein, the adsorption behaviors of environmental gas molecules, including NO, CO, O

In this paper, by analyzing the probability density function of sub Gaussian source signal in Extend-Infomax algorithm, the hyperbolic tangent function in the algorithm is changed to hyperbolic tangent function with adjustable parameter. This change is based on the fact that when the expectation of the source signal is constant, the non Gaussian property of the output signal of the separation system increases with the increase of the parameters, which will improve the performance evaluations of the Extend-Infomax algorithm. Matlab simulation results show the effectiveness of this improvement.

MoS2 is a promising candidate for hydrogen evolution reaction (HER), while its active sites are mainly distributed on the edge sites rather than the basal plane sites. Herein, a strategy to overcome the inertness of the MoS2 basal surface and achieve high HER activity by combining single-boron catalyst and compressive strain was reported through density functional theory (DFT) computations. The ab initio molecular dynamics (AIMD) simulation on B@MoS2 suggests high thermodynamic and kinetic stability. We found that the rather strong adsorption of hydrogen by B@MoS2 can be alleviated by stress engineering. The optimal stress of −7% can achieve a nearly zero value of ΔGH (~ −0.084 eV), which is close to that of the ideal Pt-SACs for HER. The novel HER activity is attributed to (i) the B-doping brings the active site to the basal plane of MoS2 and reduces the band-gap, thereby increasing the conductivity; (ii) the compressive stress regulates the number of charge transfer between (H)-(B)-(MoS2), weakening the adsorption energy of hydrogen on B@MoS2. Moreover, we constructed a SiN/B@MoS2 heterojunction, which introduces an 8.6% compressive stress for B@MoS2 and yields an ideal ΔGH. This work provides an effective means to achieve high intrinsic HER activity for MoS2.

Electrolysis of seawater makes full use of this natural resource and continuously turns it into a clean fuel, hydrogen. Electrocatalysts for seawater electrolysis must maintain a steady-state operation without suffering from chloride corrosion. In this study, we report a three-dimensional structure metal phosphide electrocatalyst by depositing cobalt-doped Fe2P (Co-Fe2P) on Ni foam. Density functional theory calculations showed that Co-Fe2P was beneficial for the hydrogen evolution reaction (HER) because of its suitable H* adsorption. Thus, the as-prepared Co-Fe2P acted as an efficient bifunctional electrocatalyst, exhibiting enhanced electrocatalytic properties for both the oxygen evolution reaction (OER) and HER. Moreover, the simulated alkaline seawater was used to determine the optimum potential (1.69 V at 100 mA cm−2) required for seawater splitting using the as-synthesized electrocatalyst. This study proposes a novel material for electrocatalytic application.

Two-dimensional (2D) hydrogen evolution reaction (HER) electrocatalysts have attracted great attention due to their unique electronic properties and high activities. Recently, a new 2D monolayer material of MoSi2N4 has been successfully synthesized and its semiconducting property and excellent ambient stability have also been demonstrated (Science 2020, 369, 670). Here, a systematic screening of catalysts for HER among N- and Si-defective MoSi2N4-supported single non-precious transition metal (TM) and non-metal (NM) atom catalysts is performed by means of density functional theory (DFT) calculations. Interestingly, the single O/P/Fe/Nb atom doped N-(Si-) defective MoSi2N4 monolayer were found to possess excellent HER performance presenting a near-zero ΔGH, which is comparable to or even better than the state-of-the-art Pt-based materials. Moreover, the novel HER activities of some TM doped structures were explained by the “states filling” model. The energy level of the first available unoccupied states for accommodating hydrogen drops after the introduction of TM atom, which modulates the hydrogen binding strength. This work opens the door for the application of MoSi2N4 monolayer and other related 2D materials in the field of energy conversion.

The electrocatalytic reduction of naturally abundant N2 to NH3 is an attractive approach to replace the Haber–Bosch nitrogen-fixation process that causes enormous energy consumption and greenhouse gas emissions. However, designing high-performance catalysts toward the electrocatalytic N2 reduction reaction (eNRR) remains one of the greatest challenges in this area. Herein, high-throughput screening of catalysts for the NRR among a series of transition metal atoms supported on a defective hexagonal boron nitride (h-BN) nanosheet is performed through spin-polarized density functional theory (DFT) computations. Strikingly, among the 18 candidates, the V/Tc atom anchored on a defective h-BN monolayer (V@BN and Tc@BN) showed good NRR activity with relatively low onset potentials. Particularly, V@BN was found to exhibit outstanding catalytic activity for the NRR via an enzymatic pathway with an extremely low overpotential of 0.25 V. The value is significantly lower than that on the Ru (0001) stepped surface that has the best NRR catalytic performance among bulk metal catalysts. The novel NRR activity of V@BN is attributed to the enhanced electrical conductivity due to V-doping, the “donation–backdonation” process for N2 activation, and the highly centralized spin-polarization on the V atom. This work not only provides a quite promising catalyst for the NRR but also provides new insights for the rational design of single-atom NRR catalysts.

Herein, we developed a reductant-free strategy to fabricate oxygen vacancies-mediated (OVs-mediated) TiO2 nanocrystals. Different from the conventional reduction process, OVs-mediated TiO2 were synthesized via a low-temperature calcination in nitrogen atmosphere assisted solvothermal process. Firstly, the pristine TiO2 was synthesized by solvothermal process using the tetra-n-butyl titanate as precursor and ethanol as solvent. Because of the organic precursor and solvent, the obtained pristine TiO2 was inevitably carbon-doped. Then, low-temperature calcination in nitrogen atmosphere instead of reducing gas atmosphere was carried out to introduce the OVs into the pristine TiO2. Experimental and theoretical results revealed that the intrinsic carbon-doping was conducive to the formation of OVs. Moreover, the obtained OVs-mediated TiO2 exhibited outstanding photocatalytic performance in comparison with the commercial P25, which was attributed to the crucial roles of OVs. This work not only provided a novel synthesis of OVs-mediated TiO2, but also contributed to understanding the crucial roles of OVs.

MoS2, as a low-cost catalyst for hydrogen evolution reaction (HER), suffers from poor catalytic performance on the basal plane. Herein, by doping 19 main-group elements on the S-defective MoS2 nanosheet, the most promising MoS2-based catalysts for the HER are screened with high-throughput density functional theory (DFT) calculations. Remarkably, the doping of main-group elements except chalcogens can improve the activity of the MoS2 basal plane to a certain extent. The S-defective MoS2 monolayer doped with In/Ge atom (In3@MoS2 and Ge3@MoS2) show excellent HER performance, and their reaction barrier is even lower than that of commercial Pt/C catalyst. In In3@MoS2 and Ge3@MoS2, the In/Ge atoms act as electron donors to increase the unoccupied anti-bonding orbital, which enhances the interaction of In/Ge-H bonding. On the other hand, the unique co-existence of electron-depletion and electron-accumulation regions near In/Ge atoms enables the adsorption of free radical H to be moderate. Moreover, the In/Ge atoms also increase the conductivity of MoS2, especially the In atom brings a new impurity state near the Fermi level. This work presents a promising strategy for exploiting high-performance MoS2-based catalysts for HER, and would stimulate more researchers to optimize other two-dimensional materials by doping main-group elements for HER.

The carbon vacancies and hydroxyls co-modified CN (CH CN) was successfully prepared using a green hydrothermal method. During the hydrothermal process, the water played an important role in etching the unstable partial of bulk CN to introduce carbon vacancies and hydroxyls into the CH CN nanosheets. The carbon vacancies and hydroxyls co-modified CH CN displayed 2.2 times higher photocatalytic NO removal performance than that of pristine CN. Detailed experimental characterizations and density functional theory calculations revealed that the enhanced photocatalytic NO removal performance of CH CN nanosheet was largely ascribed to synergistic effects of carbon vacancies and hydroxyls. The carbon vacancies could narrow the bandgap of modified CH CN nanosheet to improve the light-absorbing capability; the hydroxyls enabled to form stable covalent bonds acted as electron transport channels to facilitate the charge carrier separation. This study may provide new insights into vacancies engineering for enhancing the photocatalytic activity of CN-based photocatalysts.

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.