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In this work, mesoporous N-doped carbon (MNC) materials have been successfully prepared by a nanocasting route using SBA-15 as the template and ethylenediamine (EDA) and carbon tetrachloride (CTC) as carbon nitride precursors. The specific surface area and pore size of the MNC, as well as the C/N content are strongly dependent on the pyrolysis temperature. The as-obtained MNC-supported NiPt nanoparticles (NPs) were used as efficient catalysts toward complete dehydrogenation of hydrazine borane (HB) in alkaline solution at room temperature. Among all the catalysts investigated, the Ni60Pt40/MNC-800 nanocomposites (NCs) show the highest catalytic activity and 100% hydrogen selectivity. The total turnover frequency (TOF) of Ni60Pt40/MNC-800 NCs reached 1111 h−1 at room temperature, the highest activity among all catalysts reported to date. The superior catalytic properties were possibly a result of the electronic interaction between Ni and Pt, the synergistic effects of the NiPt NPs and MNC support, the ordered pore structure for free mass transfer and the small-sized metal NPs.

Hydrazine borane (N2H4BH3, 15.4 wt%) and hydrous hydrazine (N2H4·H2O, 8 wt%) are promising chemical hydrogen storage materials that have attracted much attention in recent years due to their high gravimetric hydrogen capacities. The selective and rapid catalytic dehydrogenation of N2H4BH3 and N2H4·H2O is the key to the potential use of the abovementioned materials in hydrogen applications. In this study, a series of Rh-MoOx nanoparticles (NPs) with various metal compositions have been successfully prepared via a simple one-step chemical reduction approach in the absence of a surfactant/support at room temperature. The obtained surfactant/support-free Rh-MoOx NPs exhibit good dispersibility and small particle size. Among all of the as-prepared Rh-MoOx NPs, the optimized Rh-MoOx catalysts with a molar ratio of 1:1 show the highest catalytic properties with 100% H2 selectivity for hydrogen evolution from aqueous N2H4BH3 and N2H4·H2O solutions at 323 K under alkaline conditions. The turnover frequency (TOF) values of Rh0.5(MoOx)0.5 NPs are 2000 and 750 h−1 for hydrogen evolution from N2H4BH3 and N2H4·H2O, respectively, which are among the highest values ever reported for Rh-based catalysts. The superior catalytic performances could be attributed to the small particles size, low crystallinity, modified electronic structure, and strong basic sites of Rh NPs induced by the MoOx dopant. The highly rapid and selective Rh-MoOx catalyst may further encourage the deployment and application of N2H4BH3 and N2H4·H2O as safe and convenient sources of hydrogen for fuel cells.

Recently, the utilization of hydrazine borane (N2H4BH3) and hydrous hydrazine (N2H4·H2O) as promising hydrogen carriers has received increasing research interest. In this work, NiIr alloy nanoparticles (NPs) immobilized on lanthanum oxy-carbonate (NiIr/La2O2CO3) have been successfully synthesized through a sodium–hydroxide-assisted reduction approach at room temperature. It was found that ultrafine NiIr NPs with an average size of around 2.3 nm were effectively and highly dispersed on La2O2CO3. NiIr/La2O2CO3 nanocomposites (NCs) prepared with the assistance of NaOH showed much higher catalytic activity and H2 selectivity toward the N2H4BH3 dehydrogenation reaction as compared to those of NiIr/La2O2CO3–N prepared without addition of NaOH. Among all of the tested samples, the optimized Ni0.75Ir0.25/La2O2CO3 NCs exhibited the highest catalytic performance with 100% hydrogen selectivity for hydrogen generation from an aqueous solution of N2H4BH3. The total turnover frequency (TOF) of Ni0.75Ir0.25/La2O2CO3 NCs for this dehydrogenation reaction was found to be 1250 h−1 at 323 K, which is among the highest values ever reported. Additionally, this catalyst also exhibited a remarkable catalytic performance for efficient and complete decomposition of N2H4·H2O. This excellent catalytic performance could be attributed to the high dispersion of metal NPs and the strong interaction between the metal and support as well as the promotion effect of NaOH.

Hydrogen has been considered as an important alternative energy source for both environmental and economic reasons. The development of highly efficient and selective catalysts for hydrogen evolution from chemical hydrogen storage materials (e.g. hydrous hydrazine, N2H4·H2O) has become one of the most active research areas. In this study, MoOx-doped NiPt nanoparticles (NPs) have been successfully prepared via a simple one-step co-reduction strategy at room temperature. The characterization results show that the surfactant/support-free NiPt–MoOx NPs with a mean particle size of 5.0 nm are well-dispersed and in a low-crystalline/amorphous state. It is found that the prepared NiPt–MoOx samples show much higher catalytic activity toward the decomposition of N2H4 as compared to that of NiPt without the introduction of MoOx. In addition, among all the NiPt–MoOx NPs, the optimized Ni0.6Pt0.4–MoOx nanocatalyst shows 100% H2 selectivity and the best catalytic performance for the decomposition of N2H4 under alkaline conditions at 323 K. The TOF value of Ni0.6Pt0.4–MoOx NPs is found to be 822 h−1, which is among the highest values ever report for the same reaction. The excellent catalytic activities could be attributed to the modified electronic structure and the small particle size of NiPt NPs induced by the MoOx dopant. Other MoOx-doped Ni-based (NiM, M = Rh, Ir, Au, Ag and Ru) bimetallic catalysts also showed excellent catalytic activity. The present highly efficient and selective catalyst system may encourage the practical application of N2H4·H2O as a potential chemical hydrogen storage material.

Hydrogen is a potentially ideal alternative energy source for both environmental and economic reasons. The development of sustainable, efficient, and economical catalysts towards hydrogen generation from hydrogen storage materials (e.g., ammonia borane, AB) has been one of the active and challenging research areas. In this work, noble-metal-free CuCoMo nanoparticles (NPs) without any surfactant or support have been prepared via a facile co-reduction method at room temperature and used as highly efficient catalysts for hydrogen generation from an aqueous AB solution. Compared to their monometallic and bimetallic counterparts, the obtained trimetallic Cu0.72Co0.18Mo0.1 NPs exhibit the highest catalytic activity for the hydrolysis of AB with a total turnover frequency (TOF) value of 46.0 min−1 at room temperature under ambient atmosphere. The Cu0.72Co0.18Mo0.1 NPs only needed 0.63 min to completely hydrolyse AB in the presence of a basic solution (NaOH, 1 M) with a TOF value as high as 119.0 min−1 at room temperature, which is among the highest values of all the noble-metal-free catalysts ever reported for the same reaction, wherein NaOH plays an important role in improving the catalytic activity. In addition, it is found that the hydrogen generation rate can be improved by adding a base (e.g., NaOH, KOH, etc.) into the reaction solution, while the presence of NH4+ species (e.g., NH3·H2O, NH4Cl, etc.) is unfavorable for the hydrolysis of AB.

A transmission reflection selective ultranarrow-band metamaterial filter based on electromagnetically induced transparency (EIT) operating at visible wavelengths is demonstrated theoretically and experimentally. The theoretical work starts with the design of an EIT structure with two separate resonance parts. Then the two resonance parts are connected and the hardness of the metamaterial filter is further increased by adding a glass substrate. Numerical simulation results show that the metamaterial filter not only exhibits ultranarrow-band transmission reflection selective spectra, but also exhibits wavelength tunable spectra for both transmission and reflection. To verify the simulation results, a filter sample is fabricated and the spectral responses are measured.

A nonpolarizing narrow band metamaterial transmission filter based on EIT operating at visible wavelengths is demonstrated theoretically and experimentally. The two separated resonance components that are able to generate EIT effect are connected using a SiO2 film layer and the hardness of the metamaterial filter is further improved by adding a glass substrate. The theoretical results are calculated by using the finite-difference time-domain simulation method and a metamaterial filter sample is fabricated and measured to verify the simulation spectrum. The full width at half-maximums of simulation and measured spectra are 0.74 nm and 1.61 nm respectively. Electric field distributions are also calculated to illustrate the physical mechanism. The novel method might be helpful to improve the processability of the narrow band metamaterial transmission filter, and also to further promote the applications of this kind of metamaterial filter.

As an ideal hydrogen supplier in liquid phase, hydrous hydrazine has gained a lot of attention for safe and efficient storage as well as transportation of hydrogen. Herein, a low Pt-containing Ni–Pt bimetallic catalyst immobilized on novel MIL-101/rGO composite has been prepared by a facile impregnation-reduction approach. Unexpectedly, the resultant Ni0.9Pt0.1/MIL-101/rGO catalyst exhibits optimal catalytic performance and 100% H2 selectivity for hydrogen evolution from hydrous hydrazine under alkaline conditions at 323 K, giving a turnover frequency (TOF) value of 960.0 h−1, which is a relatively higher value ever reported heterogeneous catalysts. Even at room temperature, Ni0.9Pt0.1/MIL-101/rGO catalyst shows excellent catalytic activity for dehydrogenation of hydrazine as well as hydrazine borane. In addition, the Ni0.9Pt0.1/MIL-101/rGO catalyst also exhibits excellent durability. Even after eight recycles, the catalytic activity is no significant decrease, and the H2 selectivity still remains 100%.