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Successful conversion of CO2 into C2 products requires the development of new catalysts that overcome the difficulties in efficient light harvesting and CO–CO coupling. Herein, density functional theory (DFT) is used to assess the photoreduction properties of nitrogen-doped black phosphorus. The geometric structure, redox potential, first step of hydrogenation activation, CO desorption, and CO–CO coupling are systematically calculated, based on which the diatomic nitrogen-doped black phosphorus (N2@BPV) stands out. The calculated results of the CO2RR pathway demonstrate that N2@BPV has excellent selectivity and high activity for CH3CH2OH production. The results of the time-dependent ab initio nonadiabatic molecular dynamics simulation show that the diatomic N active sites of N2@BPV facilitate charge separation and inhibit electron–hole recombination. In addition, the activation mechanism of CO2 is studied. The main reason for CO2 activation is attributed to the imbalance in electron transfer that destroys the symmetry of CO2. We expect that our study will offer some theoretical guidance in CO2 conversion. [ABSTRACT FROM AUTHOR]

The rational construction of photocatalysts possesses tremendous potential to solve the energy crisis and environmental pollution; however, designing a catalyst for solar-driven overall water-splitting remains a great challenge. Herein, we propose a new MoS2-based photocatalyst (Co–P@MoS2), which skillfully uses the cobalt (Co) atom to stimulate in-plane S atoms and employs the phosphorus (P) atom to stabilize the basal plane by forming the Co–P bands. Using density functional theory (DFT), it was found that oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) can occur at the P site and S2 site of the Co–P@MoS2, respectively, and the dual-active sites successfully makes a delicate balance between the adsorption and dissociation of hydrogen. Furthermore, the improved overall water-splitting performance of Co–P@MoS2 was verified by analyzing the results of the electron structure and the dynamics of photogenerated carries. It was found that the imbalance of electron transfer caused by the introduction of the Co atom was the main contributor to the catalytic activity of Co–P@MoS2. Our study broadens the idea of developing photocatalysts for the overall water-splitting. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon materials with highly porous structures and interconnected ultrathin frameworks have shown outstanding features for electrocatalytic applications. Herein, we propose a self-assembly strategy to prepare nitrogen-doped carbon sponge (NCS) with high porosity, an ultrathin framework, and a high content of active nitrogen species for high performance oxygen reduction reaction (ORR) by direct pyrolysis of the polymeric precursor. Amphiphilic poly(amic acid) (PAA) can self-assemble into a highly porous sponge-like structure (donated as PAA sponge). After pyrolysis, the high porosity and ultrathin framework of the PAA sponge are well inherited. The nitrogen species in the PAA sponge convert to pyridinic and graphitic nitrogen when pyrolyzed at 800 °C to give NCS-800, corresponding to an atomic percent of 4.6%, which are believed to be the origin of ORR catalytic activity. The NCS-800 shows high catalytic performance toward the ORR and superior methanol tolerance and long-term stability in comparison to Pt/C. After 30 hours, the relative current density is still as high as 92.4%, which is much higher than that of Pt/C (73.7%). This strategy can be extended to facilely prepare doped carbon materials with tailored morphologies and heteroatom species by choosing appropriate monomers from the abundant library of diamines and dianhydrides. [ABSTRACT FROM AUTHOR]

Eliminating the use of precious metals as cocatalysts and using visible light are two important aspects in the field of photocatalytic H2 evolution with polyoxometalates (POMs) as photosensitizers. Here we present two new POM-based materials: [CuII5(2-ptz)6(H2O)4(GeW12O40)]·4H2O (1) and [CuI2(ppz)4][H2GeW12O40]·8H2O (2) (2-ptz = 5-(2-pyridyl) tetrazole, ppz = 3-(pyrid-4-yl) pyrazole) synthesized with the Keggin type [GeW12O40]4− (GeW12) polyanion and copper-azole complexes. The optimum photocatalytic H2 evolution rate of compound 1 without a noble metal cocatalyst is 3813 μmol g−1 h−1, which is 7.6 times higher than that of compound 2 and more than 27 times higher than that of bare GeW12 polyanions. The improved photocatalytic H2 evolution rate of compound 1 is mainly attributed to: (i) the formation of stable heteropoly blue species that can absorb visible light, (ii) the large differences in the reduction potentials of the GeW12 polyanion and the copper complexes that inhibit photogenerated electron–hole pair recombination and (iii) the good dispersion of the GeW12 polyanions, thanks to the presence of [CuII5(2-ptz)6(H2O)4]n4n+ layers that preclude their aggregation. To the best of our knowledge, compound 1 is the photosensitizer for H2 evolution with the highest photocatalytic performance of all the classical POM-based materials. [ABSTRACT FROM AUTHOR]

A new polyoxometelate (POM)-based host–guest supramolecular network, [MnII(L)3]2(SiW12O40)·4H2O (L = 3-pyraziny-1,2,4-triazole), was synthesized by the hydrothermal reaction, and characterized by single crystal X-ray diffraction, infrared spectroscopy, powder X-ray diffraction and solid-state ultraviolet visible diffuse reflection. The compound is composed of Keggin type [SiW12O40]2− anion (SiW12) and manganese–L complex. A structural feature for the compound is that the manganese–L complexes are arranged to construct a host–guest network with two types of channels (the small and big ones), and the [SiW12O40]2− as guests are only encapsulated in holes of the big channels. The whole network is still highly open due to possessing vacant channels and therefore H2O and H+ can diffuse through these vacant channels with ease. Hence, it is a favourite for imposing more photo-active sites ([SiW12O40]2− and Mn) for H2O and H+. Consequently, the photocatalytic hydrogen productivity of the title compound can reach 337.76 μmol−1 g−1 h−1, which is much higher than the 6.31 μmol g−1 h−1 of its parent (TBA)4SiW12O40 POM under identical experimental conditions. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a promising clean and renewable energy source. Thus, efficient and inexpensive electrocatalysts for the HER have attracted considerable attention. Here, we report a two-step method for the synthesis of a unique CoMoO4–Co2Mo3O8 heterostructure. The CoMoO4–Co2Mo3O8 heterostructure exhibited superior HER activity that included a low overpotential of 57 mV, a Tafel slope of 55 mV dec−1 in a 1 M KOH solution, and excellent long-term stability given its high intrinsic activity and superior conductivity. Density functional theory calculations indicated that CoMoO4 and Co2Mo3O8 synergistically optimized electron distribution to reduce hydrogen adsorption energy and significantly enhance electrocatalytic activity. Our work may provide novel ideas for improving the HER performance of valence-rich transition element oxides. [ABSTRACT FROM AUTHOR]

Great progress has been made in the preparation and application of multi-shelled hollow micro-/nanostructures during the past decade. However, the synthetic methodologies and potential applications of these novel and interesting materials have not been reviewed comprehensively in the literature. In the current review we first describe different synthetic methodologies for multi-shelled hollow micro-/nanostructures as well as their compositional and geometric manipulation and then review their applications in energy conversion and storage, sensors, photocatalysis, and drug delivery. The correlation between the geometric properties of multi-shelled hollow micro-/nanostructures and their specific performance in relevant applications are highlighted. These results demonstrate that the geometry has a direct impact on the properties and potential applications of such materials. Finally, the emerging challenges and future development of multi-shelled hollow micro-/nanostructures are further discussed. [ABSTRACT FROM AUTHOR]

The rational construction of photocatalysts possesses tremendous potential to solve the energy crisis and environmental pollution; however, designing a catalyst for solar-driven overall water-splitting remains a great challenge. Herein, we propose a new MoS 2 -based photocatalyst (Co-P@MoS 2 ), which skillfully uses the cobalt (Co) atom to stimulate in-plane S atoms and employs the phosphorus (P) atom to stabilize the basal plane by forming the Co-P bands. Using density functional theory (DFT), it was found that oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) can occur at the P site and S2 site of the Co-P@MoS 2 , respectively, and the dual-active sites successfully makes a delicate balance between the adsorption and dissociation of hydrogen. Furthermore, the improved overall water-splitting performance of Co-P@MoS 2 was verified by analyzing the results of the electron structure and the dynamics of photogenerated carries. It was found that the imbalance of electron transfer caused by the introduction of the Co atom was the main contributor to the catalytic activity of Co-P@MoS 2 . Our study broadens the idea of developing photocatalysts for the overall water-splitting.

Hierarchically porous carbon nanomaterials have shown significant potential in electrochemical energy storage due to the promoted charge and mass transfer. Herein, a facile template-free method is proposed to prepare nitrogen-doped carbon superstructures (N-CSs) with multi-level pores by pyrolysis of polymeric precursors derived from the intramolecular cyclization-induced crystallization-driven self-assembly (ICI-CDSA) of poly(amic acid) (PAA). The excellent thermal stability of PAA enables the N-CSs to inherit the hierarchical structure of the precursors during pyrolysis, which facilitates the formation of meso- and macropores while the decomposition of the precursors promotes the creation of micropores. Electrochemical tests demonstrate the ultrahigh surface-area-normalized capacitance (76.5 μF cm -2 ) of the N-CSs facilitated by the hierarchically porous structure, promoting the charge and mass transfer, as well as the high utilization of pyridinic and pyrrolic nitrogen (12.9%) to provide significant pseudocapacitance contribution up to 40.6%. Considering the diversity of monomers of PAA, this ICI-CDSA strategy could be extended to prepare carbon nanomaterials with various morphologies, pore structures and chemical compositions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The energy and environmental crises have forced us to search for a new green energy source and develop energy storage and environmental restoration technologies. Fabrication of carbon functional materials derived from coal has attracted increasing attention in the energy storage and gas adsorption fields. In this study, an N, O-co-doped porous carbon/carbon nanotube composite was prepared by functionalizing coal-based porous carbon with carbon nanotubes (CNTs) and ionic liquid via annealing. The resulting material not only inherited the morphology of CNTs and porous carbon, but also developed a three dimensional (3D) hierarchical porous structure with numerous heteroatom groups. The N, O co-doped porous carbon/CNT composite (N, O-PC-CNTs) showed a surface area of 2164 m 2 g -1 , and a high level of N/O dopants (8.0 and 3.0 at%, respectively). Benefiting from such merits, N, O-PC-CNTs exhibited a rather high specific capacitance of 287 F g -1 at a current density of 0.2 A g -1 and a high rate capability (70% and 64% capacitance retention at 10 and 50 A g -1 , respectively) in a three electrode system. Furthermore, an N, O-PC-CNT symmetrical supercapacitor showed a high cycling stability with 95% capacitance retention after 20 000 cycles at 20 A g -1 and an energy density of 4.5 W h kg -1 at a power density of 12.5 kW kg -1 in 6 mol L -1 KOH electrolyte. As a CO 2 adsorbent, N, O-PC-CNTs exhibited a high CO 2 uptake of 5.7 and 3.7 mmol g -1 at 1 bar at 273 and 298 K, respectively. Moreover, N, O-PC-CNTs showed cycling stability with 94% retention of the initial CO 2 adsorption capacity at 298 K over 10 cycles. This report introduces a strategy to design a coal based porous carbon composite for use in efficient supercapacitor electrodes and CO 2 adsorbents., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)