Boron carbide (B4C) has high active electrons due to its density of state localization, so it can be used as an active site to activate CO2 molecules. At the same...

In this paper, the positive and negative charges in the silicon carbide catalyst are separated by mechanical force to produce piezoelectric effect. Under the action of piezoelectric effect, the positive and negative charges formed on the surface of silicon carbide further react with carbon dioxide and intermediate species, which drives the reduction reaction of carbon dioxide. Through design experiments and density functional theory calculations, the "on-off" effect of piezoelectric effect in carbon dioxide reduction reaction and the catalytic reaction mechanism are clarified. The results show that the piezoelectric effect makes the electrons transfer from the C atom of the active site of silicon carbide to the C-C bond formed with the adsorbed carbon dioxide, and at the same time, the electrons on the C=O bond in carbon dioxide transfer to the O atom, which promotes the adsorption and activation of CO2 molecules. Piezoelectric action changed the electron transport path of the intermediate species *COOH, successfully activated *COOH, weakened the C-O bond and increased the electron density on the O atom, making it easier for H+ to attack the O atom and then generate the key intermediate species *CO. Without piezoelectric action, this step could not happen, so the piezoelectric effect played a "switch" role. In addition, the C-C coupling in the reaction is not the traditional C-C coupling between *CO, but through the (*CHO+*CO→ *CHOCO) path, and then through a series of catalytic hydrogenation reactions, the reduction of carbon dioxide to methanol and ethanol is realized at room temperature.

In the process of synthesizing hydrogen peroxide from water and oxygen at room temperature, the reaction of water or its hydrogen ions with either oxygen or superoxide radicals is thermodynamically unfavorable (ΔGθ > 0) and also has a high activation energy. This significantly limits the progress of the reaction and the manifestation of its activity. To solve this problem, this paper found through density functional theory simulation budget that the frictional catalysis of amorphous strontium barium titanooxalate can activate the proton alcohol solvent, so that it can release highly active hydrogen protons that react preferentially with oxygen, and the alcohol that loses hydrogen protons can be combined with hydrogen protons in aqueous solution to "recover", thus acting as a hydrogen proton "transfer station" to cycle out highly active proton hydrogen. This highly active protonic hydrogen readily combines with oxygen to form hydrogen peroxide. Therefore, the tribocatalytic effect of amorphous strontium barium titanooxalate can overcome the thermodynamic prohibitions and high activation energy that limit the reaction between water and oxygen, thereby efficiently synthesizing hydrogen peroxide. Corresponding experimental results also prove this budget result.

In the two-electron transfer water splitting process (2H2O = H2O2 + H2), the conversion process of the intermediate product hydrogen peroxide is the key to determine the selectivity and efficiency of hydrogen evolution. In the paper, the friction-driven regulation of SiC catalyzed water splitting reaction can avoid the occurrence of hydrogen peroxide (oxidation) to generate oxygen reaction (H2O2 -> 1 2O2 + H2O), and instead homogenize hydrogen peroxide to form hydroxyl radicals (H2O2 -> 2 & sdot;OH), thereby greatly improving the hydrogen selectivity. At the same time, the homogenous cracking of the intermediate hydrogen peroxide relieves the restriction of the rate control step of hydrogen peroxide oxidation, it promotes the forward progress of the water splitting reaction, avoids catalyst poisoning, and effectively promotes the ability of water to decompose hydrogen. Among them, the interaction between the efficient separation of charges provide by friction and the catalytic effect of SiC is the key to control the direction of the hydrogen peroxide splitting reaction.

The paper clarifies the two electron transfer mechanism of water splitting of TiB2 under tribocatalysis. The results of the paper show that under the action of multifunctional TiB2, taking advantage of the characteristics of tribocatalysis, it not only solves the problem of hydrogen evolution selectivity in pure water splitting, but also avoids the limitation of hydrogen peroxide on the reaction rate, and finally greatly improves the efficiency of water splitting hydrogen evolution reaction. In the paper, TiB2 exhibits four excellent functions under the action of friction. The four functions of TiB2 are: First, the surface of TiB2 can continuously generate a large number of positive and negative charges by tribocatalysis. Second, it can efficiently catalyze the water splitting reaction. Third, it is extremely easy to catalyze water splitting and positive charges to form hydroxyl radicals and oxygen to form superoxide radicals. Final, it is very easy to decompose the intermediate hydrogen peroxide. TiB2 provides sufficient electrons for water splitting hydrogen evolution reaction through tribocatalysis, and simultaneously decomposes hydrogen peroxide to break the speed control step. It improves the reaction rate and avoids the poisoning effect of hydrogen peroxide. The positive charge reacts with water to release a large amount of hydrogen ions, which become the hydrogen ion source for the hydrogen evolution reaction. The oxygen liberated by hydrogen peroxide is further catalytically converted to form superoxide radicals, which greatly promotes the forward progress of the water splitting reaction.

At ambient conditions, boron nitride (BN) is incapable of catalyzing the liquid-phase synthesis of hydrogen peroxide from oxygen and water. However, experiments have demonstrated that friction can significantly enhance the efficiency of this reaction. Under certain experimental conditions, the yield of hydrogen peroxide reached 8374.58 mu mol/L/g. This study utilizes density functional theory (DFT) and associated experimental calculations to investigate the mechanism by which oxygen is reduced in water to form hydrogen peroxide. The application of frictional force enables the continuous generation of a substantial amount of hydrogen ions and superoxide radicals, thus facilitating the reaction. The process primarily proceeds through two pathways: O2 -> center dot O2 - -> center dot OOH -> H2O2 and O2 + 2q- + 2H+ -> H2O2.

The decomposition of hydrogen peroxide is an essential intermediate step in the kinetically advantageous two electrons in the process of splitting water ( 2 H2O = H2O2 + H2, H2O2- 1 2 O 2 + H2O). Although it is an exothermic reaction, the reaction rate is slow without catalyst. It is possible to significantly improve the efficiency of water splitting if hydrogen peroxide can be decomposed in a timely and rapid manner. Hydrogen peroxide can be quickly decomposed by tribocatalysis process to solve the above problems. In the process of friction catalysis, when external force is applied to piezoelectric material B4C, internal charge separation will be generated and local electric field will be formed. Tribocatalysis can continuously generate rapidly separated electrons and positive charges, which provide sufficient electrons for the two-electron water splitting process. At the same time, under the tribocatalysis of boron carbide (B4C), water molecules are easily combined with positive charges to form hydroxyl radicals and release hydrogen ions. It provides a continuous source of hydrogen ions for the generation of hydrogen, which consumes positive charges and improves the utilization efficiency of electrons. Finally, two moles of hydroxyl radicals quickly form hydrogen peroxide, which is rapidly decomposed by tribocatalysis, thus solving the bottleneck problem of two-electron water splitting. Under tribocatalyticdriven, the dual function of B4C: catalytic water splitting and decomposition of hydrogen peroxide is the key to its efficient catalytic continuous production of hydrogen and oxygen.

Ammonia synthesis by nitrogen and water reaction is essentially a process of nitrogen and hydrogen ion coupling, with electrons forming an N-H bond. In this paper, friction can continuously provide electrons and hydrogen ions in the catalytic reaction of Si3N4 to realize the nitrogen fixation process, so as to achieve high efficiency of friction catalytic nitrogen fixation at room temperature. For the direct nitrogen fixation of air and water to produce ammonia, the ammonia yield can reach 1273.4 mu mol/g at 5 h, while the ammonia yield can reach 1865.2 mu mol/g at 5 h under pure nitrogen and water nitrogen fixation. The rapid contact and separation between a PTFE rod, Si3N4 particles, and a glass reactor causes continuous positive and negative charge formation on the surface of Si3N4. The positive charges react with the sacrificial agent methanol and water to generate hydrogen ions, which not only consumes the positive charges, inhibits the recombination of positive and negative charges, and improves the utilization rate of electrons but also provides a large number of hydrogen ion sources for the reaction. Based on the results of density functional theory (DFT) calculations, which indicate that silicon atoms on the surface of silicon nitride have no catalytic activity, while nitrogen atoms can effectively activate nitrogen molecules and catalyze the nitrogen fixation reaction, we designed a tribocatalysis process to continuously break the catalyst particles to expose more surface nitrogen atoms as active sites in situ to promote the nitrogen fixation reaction. In addition, the friction force can provide energy for the reaction in the instantaneous process, which is conducive to the activation of nitrogen molecules to promote the reaction, and together with the continuous charge provided by the friction process, it finally enables Si3N4 to catalyze nitrogen fixation efficiently at room temperature.

This article reported an extremely easy method of optical radiation-assisted thermal excitation to dramatically increase photocatalytic hydrogen generation ability of water splitting with P25 as a model compound. This method compensated for the time waste, high cost and operational complexity of traditional catalytic material modification methods, and largely improved the photocatalytic hydrogen production ability of photocatalytic materials. The hydrogen generation rates at room temperature is 1090 mmol/g/h. At 50 & DEG;C, the rate increase to 10670 mmol/g/h. The quantum rates at room temperature and 50 & DEG;C are 6.5 and 63.3, respectively. It is clear that appropriate low-temperature heating could largely accelerate the hydrogen generation rate of P25.This work presents the detailed mechanism how this method largely enhances photocatalytic hydrogen generation of P25 as well as the laws. The new method offers some evidences and reference for research on how the photothermic synergistic action facilitates the photocatalytic hydrogen generation of catalytic materials.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hexagonal boron nitride (h-BN) is a graphite-like two-dimensional material with a piezoelectric nanostructure and thus is extensively applied. In this study, piezoelectric catalytic hydrogen production by h-BN was realized at the H-2 yield of 824.281 mu mol/g/h. After 5 repeated experiments, the H-2 yield did not drop significantly, indicating 2D h-BN has high piezoelectric catalytic ability and stability. Since h-BN can directly convert mechanical energy into chemical energy, deformation after machinery vibration will induce the formation of surface positive charge q(+) and negative charge q(-). The negative charge concentrates on the conduction band and binds with hydrogen ion to form hydrogen gas that can escape. It displays the huge potential of two-dimensional piezo-electric materials in relieving energy pressure.

Chirality is ubiquitous in the nature. Chiral nanomaterials show wide application prospects owing to their special properties. In this study, chirality was introduced into photocatalysis. Chiral L-cysteine was introduced into photocatalytic materials for preparation of chiral CdS quantum dots (QDs) at room temperature. Then the CdS QDs were characterized by ultraviolet-visible spectra, infrared spectra and X-ray photoelectron spectroscopy. The hydrogen production activity was tested within the visible light range. Under visible light irradiation, the hydrogen yields of chiral CdS QDs at 298, 323, 333, 348, 358 K were all higher compared with the nonchiral CdS QDs. The hydrogen yield was maximized to 18.72 mmol/g/h at 333 K, which was significantly higher than that of the nonchiral CdS QDs (10.35 mmol/g/h). The reasons for the higher activity of chiral CdS QDs were that the introduction of the chiral ligand broadened the bandgap of CdS, and the more-negative conduction band strengthened the reducibility of photoelectrons. Moreover, the electrondonating groups that coordinated with the active Cd2} directionally enhanced the electron density of CdS QDs. Theoretical calculation showed the conduction band electron density of CdS was significantly improved, which is consistent with the above results. For these reasons, the hydrogen production ability of chiral CdS QDs is considerably higher than that of nonchiral CdS QDs. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

A novel chiral Ag@Ag3PO4-NaDC composite was synthesized by chiral induction. SEM, XRD, CD spectrum, FTIR, UV–vis and XPS were used to study the physical and chemical properties of the materials, and the photocatalytic oxidation ability was evaluated with methyl orange as the target pollutant. The results show that the introduction of chirality can obviously promote the light absorption ability, broaden the band gap, enhance the oxidation ability, promote the separation of electrons and holes, greatly enhance the plasma resonance effect of silver nanoparticles, and promote the synergistic effect between silver nanoparticles and silver phosphate. Compared with Ag@Ag3PO4, the catalytic degradation ability of chiral Ag@Ag3PO4-NaDC is improved by more than 60%. Therefore, the chiral Ag@Ag3PO4-NaDC composite exhibits excellent photocatalytic performance. In the degradation of methyl orange by Ag@Ag3PO4-NaDC, a large amount of ·O2- and h+ were formed on the surface, which was the main reason for the oxidation ability.

Because (I) over cap +/- -Si3N4 has a noncentrosymmetrical crystal pattern capable of self-polarizing point groups, it is theoretically pyroelectric. When the ambient temperature changes, the surface of a pyroelectric semiconductor will produce abundant compensationary charges q(+) and q(-), which theoretically can be used into hydrogen evolution from water splitting. In this study, the piezoelectric and pyroelectric performances of alpha- Si3N4 were validated by piezoelectric force microscopy and potassium permanganate reduction experiments. Based on the pyroelectric performance of alpha- Si3N4 and with methanol as the sacrificial agent, hot-cold cycles were conducted from room temperature (27 degrees C) to 60 degrees C. Per gram of catalysts can produce 12.32 mu mol/g hydrogen after 20 cycles, and the hydrogen yields after repeated experiments did not significantly decrease, proving that Si3N4 has high stability and that the pyroelectric effect is highly potential for hydrogen production from water splitting.

The hydrogen producing performances of metal-free organic polymers PVDF and PVDF-HFP from water splitting were investigated. The 200-min hydrogen yields of PVDF and PVDF-HFP under ultrasonic vibration are up to 355.10 and 724.64 mu mol/g respectively. Because of the strong deformability and ductility, PVDF and PVDF-HFP under ultrasonic vibration were more prone to deformation, promoting their polarization to form positive and negative charges, which interacted with hydrogen ions in water to form hydrogen. The PVDF-HFP contains more beta phase and less alpha phase and thereby shows better piezoelectric catalytic performance. Because of high hydrogen producing stability, both PVDF and PVDF-HFP are highly potential in clean energy production and wastewater treatment.

In today's age of resource scarcity, the low-cost development and utilization of renewable energy, e.g., hydrogen energy, have attracted much attention in the world. In this work, cheap natural halloysite nanotubes (HNTs) were modified with γ-aminopropyltriethoxysilane (APTES), and the functionalized HNTs were used as to support metal (Pd, Au, Ag) catalysts for dehydrogenation of formic acid (DFA). The supports and fabricated catalysts were characterized with ICP, FT-IR, XRD, XPS and TEM. The functional groups facilitate the anchoring of metal particles to the supports, which brings about the high dispersion of metallic particles in catalysts. The catalysts show high activity against DFA and exhibit selectivity of 100% toward H2 at room temperature or less. The interactions between active centers and supports were investigated by evaluation and comparison of the catalytic performances of Pd/NH2-HNTs, PdAg/NH2-HNTs and PdAu/NH2-HNTs for DFA.

Morphology-dependent properties are significant in chemistry and material sciences. This laboratory experiment,designed for upper-division undergraduates in chemistry and related majors, emphasizes the concepts of the shape-controlled synthesis of crystal particles and the influences of crystal particlemorphologies on their reaction performances. Cu2O particles with different morphologies, cubic and truncated octahedral, were synthesized under mild conditions. The resulting products were examined with XRD and SEM to characterize their phasecomponents and surface morphologies. The activity differencesof these products in the reduction of ferric thiocyanate solution,K(n-3)[Fe(SCN)n], were measured and compared. The truncatedoctahedral Cu2O particles showed higher activity than the cubicones, which is attributed to differences in their shapes and exposed facets. This experiment can help undergraduates realize that the performances of crystal particles are related not only to their structures and dimensions but also to their morphologies

We use the characteristics of piezoelectric barium strontium sulfate (BSS) to collect the mechanical energy generated byball-milling to produce the piezoelectrochemical effect. At the same time,in coordination with the mechanochemical effect generated by ball-milling, toluene is oxidized to phenol in air atmosphere. Starting withcharacterization, BSS was characterized by X-ray powder diffraction(XRD), thermalfield emission scanning electron microscopy, electro-chemical test, Fourier transform infrared spectroscopy, and ultravioletvisible spectroscopy. Moreover, six reaction parameters???catalyst type,catalyst dosage, reaction time, ball-milling speed, pH value of reactionsolution, and toluene concentration???were discussed, and the optimumreaction conditions were obtained. Ultimately, the mechanism ofcatalytic reaction was discussed. It is found that the superoxide radical(center dot O2-), which formed by oxygen in the air and electrons generated by theBSS piezoelectric effect, is the main oxidation species for the oxidation of toluene. The oxidation potential of center dot O2-is-0.33 V versusNHE, which can oxidize toluene to phenol without excessive oxidation

In this study, with silicon carbide as a pyroelectric catalyst, the reactor was alternatively removed between a hot water bath and a cold water bath, which ensured the cold-hot circulation within 300-333 K at room temperature. Then the pyroelectric performance of silicon carbide was utilized in hydrogen evolution from water splitting. With methanol as the sacrificial agent, the hydrogen yield after 20 cycles was up to 32.84 limol/g. Silicon carbide demonstrates high catalytic activity and together with its chemical stability, it shows potential in hydrogen production from water splitting under cold-hot alternation.

Photocatalytic water spitting is one way of hydrogen production from energy conservation and emission reduction. However, the activities of most photocatalytic materials need to be enhanced by cocatalysts. In this study, we explored to control the photocatalytic hydrogen evolution (PHE) ability of cadmium sulfide (CdS) without any cocatalysts by temperature and largely improve its photocatalytic ability. It was experimentally found the activity of CdS without cocatalysts under heating conditions (<100 °C) was much higher than that at room temperature, and increased first and then decreased, with a maximum at 50 °C (169716 umol/h, 68.2 % , λ = 450 nm). Therefore, it is convenient to control the hydrogen production activity of CdS by temperature. The large increment of photocatalytic activity was realized because the temperature complemented the shortcomings of semiconductors in light absorption, and together with light radiation, increased the electron migration rate and density, quantity of surface adsorbed H3O+ and number of active sites, prolonged the living of electrons, and reduced the overpotential of water splitting and the reverse reactions. Heating brings the above advantages, but also exacerbates the recombination of electron-hole pairs. Therefore, the activity shows an extreme value along with the temperature rise. This work experimentally proves temperature control is one of the most efficient and simple ways to largely enhance the PHE ability.

With the continuous growth of global energy demand, the artificial photosynthetic system of photocatalytic decomposition of hydrogen production has been widely concerned, CdZnS, a photocatalyst based on solid solution, has shown good performance. In order to avoid the rapid recombination of photogenerated electron and hole, metal boride is added as a catalyst to enhance its photocatalytic hydrogen production performance. We prepared CdZnS photocatalyst by hydrothermal method, and synthesized different proportions of NiB/CdZnS catalyst by programmed heating method and calcined it at 773K. Characterized by XRD, XPS, uv-vis diffuse reflection and other methods, CZS solid solution and NiB/CdZnS were synthesized, and the absorption edge of NiB/CZS was redshifted relative to the pure CdZnS. The addition of NiB can effectively inhibit the recombination of electrons and holes to improve the separation efficiency of photogenerated charge, and its content has an impact on photocatalytic activity. We found that under visible light irradiation, when the content is 15 wt%, the hydrogen production was the highest. The optimal quantum efficiency was 13.3%, and the hydrogen production reacheed 8137 mu mol/g/h, which is 17 times that of pure CdZnS. The addition of NiB greatly improved the photocatalytic performance of CdZnS. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.