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In this paper, the effects of the sulfur vacancy (VS) distribution in 2H–MoS2 monolayer on the H2 evolution mechanism and activity are researched by density functional theory (DFT) calculations. The calculation results reveal that the H2 generation on VS follows the Volmer-Heyrovsky mechanism with the Heyrovsky reaction as the rate determined step (RDS) with an energy barrier of 18.5 kcal/mol. When two VS are separated by one S atom, the H2 evolution on VS remains the Heyrovsky-step-determined Volmer-Heyrovsky mechanism and the RDS energy barrier increases to 20.0 kcal/mol. Removing adjacent S of VS causes that the Tafel-step-determined Volmer-Tafel mechanism works for HER and the barrier of RDS increases to 21.4 kcal/mol. Though the barriers of RDS ascend when the concentration of VS is enhanced by these two strategies, the Tafel step can take place at a lower potential and more VS are exposed. Therefore, two adjacent or next-near VS may obtain better H2 generation performance. Three adjacent or spaced out VS by one S may be less favorable for HER.

In this paper, the stable CoMo6S16 clusters are built as the models of catalyst to research the H2 production reaction mechanism of Co-doped Mo-edge by density functional theory (DFT) calculations. The results show that Co and Mo on Co-doped Mo-edge are the main active sites for catalyzing H2 evolution reaction. In H2 evolution process, S including Co-activated S atoms and the S atoms on Mo-edge first gain H atoms, which can accelerate the H2 evolution on Co and Mo. Subsequently, Co and Mo at the edges efficiently catalyze the H2 evolution reactions following the Volmer–Heyrovsky mechanism, and the Volmer reactions are proved to be the rate-limiting steps. The activation barriers of the rate-limiting steps are 15.5 and 16.2 kcal mol−1, respectively, which are lower than that on Mo-edge. This implies that doping Co in 2H-MoS2 can activate S atoms on the slab of 2H-MoS2 and simultaneously enhance the H2 evolution activity of Mo-edge.

This work investigated the adsorption of Eosin Y (EY) on the surface of Ru4 and Pt4 clusters and the UV–vis adsorption of EY by the DFT and TD-DFT method, respectively. The relationship of adsorption action, adsorption energy and hydrogen production efficiency in EY-sensitized system were studied as well. It is proved that the enhancement in the interaction energy of key group in sensitizer and co-catalyst was an efficient method to improve hydrogen evolution performance. The TD-DFT calculation showed that the photoelectrons of excited state EY mainly focused on the upper surface of C5O ring with the COO− side. In the EY-Ru4 system, the maximum adsorption energy originated from the concurrent interaction of the COO− and C5O groups of EY with the Ru4 cluster was −237.8 kJ/mol, while in the EY-Pt4 system the maximum adsorption energy from the interaction between the C atom on C6 ring of EY and the Pt4 cluster was −230.5 kJ/mol. Compared with EY-Pt system, the dominating adsorption of EY on Ru was conducive to the quick transfer of photoelectron from EY to Ru. Therefore, the EY-Ru system exhibited higher hydrogen generation efficiency than the EY-Pt system.

Emodin is a natural anthraquinone derivative and contains abundant hydroxyl and carbonyl groups, which has high redox activity. As guest molecules, Emodin molecules were anchored on graphene sheet (GNS) by simple one-step reflux method. In the three-electrode system, the optimal composite electrode material (E@GNS) obtained the high specific capacitance of 338.9 F g−1 at 5 mV s−1 and excellent rate capability in 1 mol L−1 H2SO4. Finally, an asymmetric supercapacitor (ASC) was fabricated by using E@GNS as negative electrode and Caffeic acid non-covalently modified graphene hydrogel (GH-CFA) as positive electrode, respectively. The device achieved the energy density of 32.8 Wh kg−1 along with power density of 0.8 kW kg−1, and a light-emitting diode (LED) could be light up by two ASCs in series. To compare with the performance of ASC, we also assembled symmetric supercapacitor based on E@GNS, proving that the good matching of positive and negative electrode materials could make the supercapacitor exhibit the best capacitive performance.

In this paper, the reaction mechanism for N 2 O with CO on the surface of Ni 5 cluster was investigated by the B3LYP method of density functional theory (DFT). Ni atom of various species was calculated using B3LYP/ LANL2DZ basis set, and C, N, O atoms at B3LYP/6-31G ∗ level. In the temperature range of 100–1000 K, the statistical thermodynamics and Eyring transition state theory with Winger correction were used to study the kinetic characters of reaction. The calculation results indicated that the reaction of N 2 O with CO on Ni 5 cluster had two major reacting processes: (1) O atom first dissociated from N 2 O on Ni 5 cluster, and then reacted with CO on Ni 5 and (2) on the surface of Ni 5 catalyst, O atom of N 2 O direct interacted with C atom of CO, resulting into the dissociation of N 2 O and the form of CO 2 . The direct O extraction channel was the main channel due to its low potential energy and high rate constant.

In this paper, sodium polyacrylate (PAAS) was used as an assistant to markedly enhance the hydrogen generation efficiency of Eosin Y (EY) sensitized Pt photocatalyst. The molecule chain of polyacrylic acid ion adsorbed on Pt could gather EY on the surface of Pt nanoparticles, thereby enhancing the contact of EY and Pt and the utilization of photo-generated electrons generated by EY under visible light irradiation. Therefore, sodium polyacrylate stabilized Pt nanoparticles showed 3.25 times higher hydrogen generation activity than Pt-EY under the same conditions. The highest AQE of EY-PAAS 1 (m w > 30 million)-Pt system was 34.3% at 520 nm. This result provided a new approach for improving the hydrogen evolution efficiency of photocatalytic system.

5, 7, 12, 14-pentacenetetrone (PT), polycyclic quinone derivatives, are rich in carbonyl, which were investigated as a novel organic electrode material for supercapacitors. PT with a π conjugated system, is a flat molecule, generating strong π–π interactions between molecules. PT molecules were uniformly fixed on conductive reduced graphene oxide (rGO) through π–π interaction by one-step solvothermal method, forming a three-dimensional cross-linked PT@rGO hydrogel. This composite structure was conducive to reducing the charge transfer resistance and promoting the Faraday reaction of electrode, which achieved the superposition of electric double-layer capacitance and pseudocapacitance. Appropriate organic molecular loading can effectively improve electrochemical performance. The optimal PT@rGO electrode material displayed the specific capacitance of 433.2 F g−1 at 5 mV s−1 with an excellent rate capability in 1 mol l−1 H2SO4 electrolyte. Finally, the fully pseudocapacitive asymmetric supercapacitor has been assembled by using PT@rGO as positive electrode and benz[a]anthracene-7,12-quinone (BAQ) modified rGO(BAQ/rGO)as negative electrode, which exhibited the good energy storage performance in a cell voltage of 1.8 V.

A novel catalyst of platinum nanoparticles (PtNPs) decorated on polydiallyldimethylammonium chloride (PDDA) functionalized polypyrrole nanospheres (PNS) has been prepared by simple wet-chemical method. PNS with large surface area and high dispersion was prepared by chemical polymerization of pyrrole. PtNPs with uniformed size and high dispersion have been successfully decorated on PDDA functionalized PNS via a sodium borohydride reduction process. The PNS/PtNPs is characterized by transmission electron microscopy, high resolution transmission electron microscopy, energy-dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy and inductively coupled plasma spectrum instrument. The results show that the PtNPs with sizes of approximate 5–6 nm are uniformly dispersed on the surface of PNS. Compared to Vulcan XC-72 carbon black supported same mass PtNPs (XC-72/PtNPs), PNS/PtNPs show larger mass activity (374 mA mg−1) and stronger poisoning-tolerance (If/Ib = 2.85) due to high dispersion of PtNPs on large surface of PNS. The performance indicates that PNS/PtNPs may be an excellent anode catalyst for methanol oxidation reaction.

The molecular imprinted technique (MIT) is an approach to synthesize a polymer matrix with molecular recognition sites, which shows specific binding behavior to target molecules. MIT has been successfully applied in sensing areas due to their mechanical and chemical stability, high affinity and outstanding substrate recognition ability, low cost and easy preparation. Based on a gold nanoparticle/carbon nanotube hybrid material (AuNP–CNT) and molecularly imprinted polymer (MIP), we propose a novel molecularly imprinted electrochemical sensor to determine isoniazid (INH) selectively. The surfaces of glassy carbon electrodes (GCE) are modified by multi-walled carbon nanotubes (MCNT) decorated with gold nanoparticles (AuNP). The selectivity of INH detection is improved by the MIP membrane and the area of the electrochemical active surface area is increased by the AuNP–MCNT nanometer complex. INH is detected by stripping voltammetry and the effect of sound. The oxidation peak current and INH concentration have a linear relationship in the range of 1 × 10−9 to 1.4 × 10−8 M and 2 × 10−8 to 1.0 × 10−7 M, respectively. The detection limit is 0.3 × 10−9 M (3σ) INH with a relative standard deviation of 4.6% (n = 8) for 5 × 10−8 M INH after 60 s enrichment. The sensor can be applied to detect the INH in body fluid and pharmaceutical samples selectively. The solution of MIP–AuNP–MCNT/GCE exhibits remarkable advantages, such as low cost, ease to use, high selectivity and sensitivity.

The reaction mechanism of HNCS with SiHF radical has been investigated by the B3LYP method of density functional theory (DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311++G ∗∗ level. To obtain more precise energy result, stationary point energies were calculated at the G3 level. In temperature range of 100–1500 K, the statistical thermodynamics and Eyring transition state theory with Winger correction are used to study the thermodynamic and kinetic characters of the channel with low energy barrier at 1.0 Atm. HNCS + SiHF → IM1 → TS1 → SiFNHCHS(P1) was the main channel with low potential energy, SiFNHCHS was the main product. The analyses for the combining interaction between HNCS and SiHF radical with the atom-in-molecules theory (AIM) have been performed.

Functionalized gold nanoparticles (FuAuNP) have potential applications because of their specific functional groups. p-Aminothiophenol (p-ATP) possesses double functional groups that can be used to form an S–Au bond and oligoaniline. Based on molecular imprinting technology and electrochemical technology, a novel enzymeless methyl-parathion (MP) sensor has been constructed with nanocomposites. The template molecule (MP) is embedded in the imprinting sites by p-ATP molecular self-assembly and FuAuNP electro-polymerization. The imprinting effective sites and the conductive performance are improved by gold nanoparticles decorated carbon nanotube nanocomposites (AuNP–MCNT). The linear relationships between peak current and MP concentration are obtained in the range from 0.1 to 1.1 ng mL−1 and 1.1 to 11 ng mL−1, respectively. The detection limit can be achieved as low as 0.08 ng mL−1 (3σ) with relative standard deviation of 3.8% (n = 5). This sensor was also applied for the detection of MP in apples and vegetables, with average recoveries between 95.2% and 105.7% (RSD < 5%). The results mentioned above show that the novel electrochemical sensor is an ideal device for the real-time determination of MP in real samples.

In this paper, the mechanisms of H2 evolution over the Mo-Edge of 2H-MoS2 with the unsaturated Mo (MoU) and S (SU) were investigated by the density functional theory. The calculations indicated that MoU was a key active site for H2 evolution. In the process of H2 evolution, the SU firstly absorbed H atom by the Volmer reaction, which caused the aggregation of electron on MoU, resulting in the barriers reduction of H transfer and H2 evolution on MoU. The formation of molybdenum hydride was the rate-limiting step. Compared to Mo-edge in 2H-MoS2, the barrier of key step for H2 evolution on Mo-edge with SU and MoU decreased obviously. This implied that the removal fractional S from the Mo-edge of 2H-MoS2 could enhance its H2 evolution activity and the electron trapping ability of active site for H2 evolution by the Volmer-Heyrovsky reaction might affect its activity.

The reaction mechanism of radical with HNCO has been investigated by the B3LYP method of density functional theory(DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/ level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)///B3LYP/ level. was the main channel with low potential energy, was the main product. The analyses for the combining interaction between radical and HNCO with the atom-in-molecules theory (AIM) have been performed.

The reaction mechanism of SiHF radical with HNCO has been investigated by the B3LYP method of density functional theory (DFT), while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311++G** level. To obtain more precise energy result, stationary point energies were calculated at the CCSD(T)/6-311++G**//B3LYP/6-311++G** level. In temperature range of 100 K to 1900 K, the statistical thermodynamics and Eyring transition state theory with Winger correction are used to study the thermodynamic and kinetic characters of the channel with low energy barrier at 1.0 Atm. SiHF + HNCO → IM 8 → TS 8 → SiFNHCHO ( P 3) was the main channel with low potential energy in the singlet state, SiFNHCHO was the main product. The analyses for the combining interaction between SiHF radical and HNCO with the atom-in-molecules (AIM) theory have been performed. There are three reaction channels in the triplet.

We presented a theoretical study on the detailed reaction mechanism and kinetics of the HNCS molecule with the OH-. The barrierless minimum energy path and the most favorable entrance channel have been determined by study the thermodynamic and kinetic characters of the channel with low energy barrier. The B3LYP/6-311++G** method was employed for all the geometrical optimizations and a multi-level extrapolation method based on the G3 energies was employed for further energy refinements. In addition, the analysis of the combining interaction between hydroxide ion and HNCS was performed by natural bond orbitals (NBO) analysis. The calculation results indicated that the reaction of OH- with HNCS had four channels, and the channel of H-atom in HNCS direct extraction to OH- (OH-+HNCS→IM1→TS3→IM4→P2(SCN- +H2O)) in singlet state was the main channel with the low potential energy and high equilibrium constant and reaction rate constant. SCN- and H2O were main products.