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Designing highly active and selective metal nanocatalysts for use in liquid chemical hydrides is highly attractive but remains a critical challenge. Herein, bimetallic NiPt nanoparticles (NPs) immobilized on lanthanum oxycarbonate (NiPt/La2O2CO3) have been facilely synthesized via an alkali-assisted reduction method. The introduction of NaOH is the key factor to the formation of the well-dispersed and ultrafine NiPt NPs (2.8 nm). The obtained Ni0.6Pt0.4/La2O2CO3 exhibits an extraordinarily high catalytic activity and 100% H2 selectivity for hydrous hydrazine dehydrogenation, providing a turnover frequency value (TOF) high up to 490 h-1 at 298 K. Additionally, the NiPt/La2O2CO3 prepared with NaOH demonstrates higher catalytic performance and lower activation energy than that of NiPt/La2O2CO3_N prepared without NaOH. Moreover, the NiPt/La2O2CO3 also shows an outstanding catalytic efficiency (TOF = 1200 h-1) for dehydrogenation of hydrazine borane at 298 K. The efficient catalytic performance may be attributed to the small size effect, the strong metal-support interaction, and the NaOH promotion effect. This alkali-assisted reduction method provides a new perspective for preparing of highly efficient catalysts in clean energy application.

Encapsulating metal nanoparticles (MNPs) inside the specific porous materials is considered as a feasible strategy to prepare ultrafine MNPs with high stability. Herein, ultrafine Ru nanoparticles (NPs) with a mean size of 3.2 nm encapsulated in a N-doped porous carbon (NC) derived from the pyrolysis of a new porphyrin framework (POF) were fabricated via a simple wet chemical method, in which POF was synthesized using 4,4'-biphenyldicarboxaldehyde and pyrrole as raw materials. Reconstructed slices tomographic characterization confirmed the successful encapsulation of Ru NPs in POF-NC600 (pyrolysis temperature T = 600 °C). Due to the confinement effects and anchoring effects of POF-NC600, Ru@POF-NC600 shows the smallest particle size of Ru NPs and the highest hydrogen production performance toward the methanolysis of ammonia borane (AB) among the investigated catalysts, providing a record initial turnover frequency (TOF) value of 727 min-1 at 25 °C as compared to those heterogeneous catalysts ever reported. Systematic investigations reveal that pyridinic-N plays a pivotal role in the particle size distribution of Ru NPs and catalytic activity of the catalyst. Extended theoretical calculations confirm that Ru atoms attached to pyridinic-N display a higher stability than those attached to pyrrolic-N and C atoms. As a result, pyridinic-N, as an efficient anchoring site, determinates the dispersity and size distribution of Ru NPs, thus affecting the catalytic activity of the catalyst. The more pyridinic-N, the better the catalytic activity. A series of isotopic experiments were performed, and it is found for the first time that the cleavage of the O-H bond in methanol is involved in the rate-determining step (RDS) of AB methanolysis. This work offers insights into rationally designing stable and ultrafine metal NPs confined in the pyridinic-N-rich composites for various application.

Hydrous hydrazine (N2H4·H2O) has great potential as a convenient and safe hydrogen source for fuel cells. Tremendous efforts have been made to develop economic and efficient metal catalysts for hyd...

Hydrogen (H2) is becoming the most promising candidate for the future sustainable energy systems because it is clean and regenerable. Formic acid (FA, HCOOH), one of the high-value products of the ...

Hydrolytic dehydrogenation of sodium borohydride (NaBH4) has been considered as a source of hydrogen for fuel cell applications. In this work, amorphous and electron-rich Co-CeOx nanoparticles (NPs) with a small size of 4.4 nm anchored on a nitrogen-doped carbon nanosheet (NCNS) have been prepared via a simple and facile chemical reduction method, in which NCNS was obtained by carbonizing a mixture of metal–organic frameworks ZIF-8 and potassium citrate. The as-prepared Co-CeOx/NCNS catalyst possesses an outstanding catalytic activity for the catalytic hydrolysis of NaBH4 at room temperature under alkaline conditions, giving a hydrogen generation rate (HGR) value as high as 28 410 mLH2·min−1·gCo−1, which is among the highest HGR values reported to date for all catalysts. The kinetics of hydrolytic dehydrogenation of NaBH4 aqueous solution was investigated in detail. The excellent catalytic activity of Co-CeOx/NCNS can be owing to the small size and amorphous state of Co-CeOx NPs, electron-rich properties of Co NPs modulated by the CeOx promoter, strong synergistic interaction between Co-CeOx NPs and the NCNS support with a high surface area and abundant defects, and the promotion of NaOH.

Selective catalytic decomposition of hydrazine (N2H4) to provide a clean energy carrier hydrogen (H2) is a promising alternative to fossil fuels for the future energy economy. NiPt nanoparticles (NPs) dispersed on delamination of TiO2-decorated Ti3C2Tx (denoted as DT-Ti3C2Tx) nanosheets are prepared via a simple wet chemical reduction method and applied as an efficient catalyst for dehydrogenation of N2H4 in aqueous solution. The rich oxygen-containing functional groups on the surface of DT-Ti3C2Tx not only facilitate the formation and immobilization of monodisperse NiPt NPs but also enhance the synergistic effect between metal NPs and MXene support. Among all of the tested samples, the optimized Ni0.8Pt0.2/DT-Ti3C2Tx nanocatalyst exhibits the 100% H2 selectivity and best catalytic performance with a TOF value of 1220 h−1 for the selective decomposition of N2H4 at 323 K. In addition, this catalyst also shows excellent catalytic performance for hydrogen production from hydrazine borane (N2H4BH3) via the hydrolysis of borane group and selective decomposition of hydrazine moiety. The TiO2-decorated Ti3C2Tx MXene can be applied as an excellent support to obtain well-dispersed and ultrafine metal NPs for various applications.

Ultrafine NiFe nanoparticles (NPs) decorated by La(OH)3 have been successfully prepared via a facile one-step co-reduction method without the help of surfactant or support. It was found that after being decorated with La(OH)3, the NiFe–La(OH)3 NPs have a smaller particle size and lower crystallinity. The resultant NiFe–La(OH)3 nanocatalyst exhibits an excellent catalytic activity, 100% H2 selectivity, and satisfied recyclability for hydrogen evolution from hydrous hydrazine (N2H4·H2O) at 343 K under alkaline conditions, giving a high turnover frequency (TOF) value of 100.6 h−1, which is more than 35 times higher than pure NiFe NPs (2.8 h−1). The kinetics study shows that with respect to the concentration of catalyst and N2H4, the N2H4 dehydrogenation reaction follows fist-order kinetics and zero-order kinetics, respectively. Furthermore, NiFe–La(OH)3 also exhibits an outstanding performance and excellent recycle stability during high dehydrogenation of hydrazine borane (N2H4BH3). The excellent performances for the dehydrogenation of N2H4 and N2H4BH3 could be attributed to the strong interaction between La(OH)3 and NiFe NPs, as well as ultrafine and low crystalline NiFe NPs due to the addition of La(OH)3.

Hydrazine borane (N2H4BH3) has been considered as a promising chemical hydrogen storage material in recent years for its high hydrogen content (15.4 wt%), easy preparing, and good stability. Designing highly efficient and selective catalysts for realizing the hydrogen evolution from N2H4BH3 is highly attractive but still remains challenging. In this work, NiPd nanoparticles (NPs) modified with MoOx have been readily synthesized via a co-reduction route at room temperature and served as highly efficient catalysts toward hydrogen generation from N2H4BH3 in aqueous solution. Compared to the pure Ni0.6Pd0.4 NPs, the obtained Ni0.6Pd0.4-MoOx catalyst exhibits much higher catalytic performances in dehydrogenation of N2H4BH3 at 323 K, providing a total turnover frequency (TOF) value of 405 h−1 and almost 100% hydrogen selectivity. The improved catalytic activity of NiPd-MoOx catalyst may be attributed to the small particles size and increased electron density of NiPd as well as the strong basic sites of NiPd NPs induced by the MoOx dopant. The facile synthesis of high-performance and cost-effective of metal NPs catalysts is of great significance for the development of N2H4BH3 as a promising hydrogen storage material.

Hydrogen (H2), a regenerable and promising energy carrier, acts as an essential role in the construction of a sustainable energy system. Formic acid (HCOOH, FA), a natural biological metabolic products and also accessible through carbon dioxide (CO2) reduction, has a great potential to serve as a prospective H2 supplier for the fuel cell. Herein, ultrafine and electron-rich IrPdAu alloy nanoparticles with a size of 1.4 nm are highly dispersed on amine-modified mesoporous SiO2 (NH2-SBA-15) and used as a highly active and selective catalyst for fast H2 production from FA. The as-synthesized IrPdAu/NH2-SBA-15 possesses superior catalytic activity and 100% H2 selectivity with initial turnover frequency values of 6316 h-1 with the additive of sodium formate (SF) and 4737 h-1 even without SF at 298 K, comparable to the most effective heterogeneous catalysts ever published. The excellent performance of IrPdAu/NH2-SBA-15 was not only ascribed to the combination of the electronic synergistic effect of trimetallic alloys and the strong metal-support interaction effect but also attributed to the amine (-NH2) alkaline groups grafted on SBA-15, which is beneficial to boost the split of the O-H bond of FA.

Nitrogen-rich covalent organic frameworks (COFs) with a high content of nitrogen and an inherent porous skeleton are considered as a remarkable support for encapsulating active metal nanoparticles (MNPs). Herein, a cost-effective and nitrogen-rich COF (PC-COF) synthesized from piperazine and cyanuric chloride was used as a carrier for encapsulating Rh NPs via a metal–nitrogen (M–N) coordination reduction strategy. Numerous precisely tailored N atoms within the PC-COF facilitate the construction of Rh–N complexes between Rh ions and N atoms, which can be in situ reduced to produce ultrafine Rh NPs confined in the pores of the PC-COF. The optimized Rh/PC-COF catalyst shows uniform dispersibility and a fairly narrow distribution (1.4–2.6 nm) of Rh NPs, giving an ultrahigh catalytic activity for the methanolysis of ammonia borane (AB) with a total turnover frequency (TOF) of 505 min−1 at 298 K. The excellent catalytic performances can be ascribed to the ultrafine particle size, electronic-rich Rh NPs, and the synergistic effect of the Rh NPs and PC-COF. The M–N coordination reduction strategy for encapsulating ultrafine MNPs into the pores of COFs opens a valuable pathway for developing metal nanocatalysts with high catalytic performance and excellent stability.

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.

Hydrogen has attracted much attention as a globally accepted clean energy carrier. Currently, the search for safe and efficient hydrogen storage materials is one of the most difficult challenges for the upcoming hydrogen economy. Boron- and nitrogen-based hydrides, such as metal borohydrides (e.g. NaBH4), ammonia borane (NH3BH3), ammonia (NH3), hydrous hydrazine (N2H4·H2O), and hydrazine borane (N2H4BH3), have received much attention as potential chemical hydrogen storage materials because of their high hydrogen contents and the advantage of CO-free H2 produced. In recent years, substantial efforts have been devoted to research highly efficient catalysts to significantly improve the kinetic properties for hydrogen evolution from the hydrolysis of sodium borohydride and ammonia borane, and selective decomposition of ammonia, hydrous hydrazine and hydrazine borane. Among them, non-noble metal catalysts have been widely considered as potential candidates due to their low cost, abundant reserves, and relatively high catalytic activities. In this review, we focus on the recent advances in non-noble metal catalyst design, synthesis and applications in hydrogen generation from boron- and nitrogen-based hydrides.

Selective dehydrogenation of formic acid (FA, HCOOH) is a promising alternative to fossil fuels, to provide a clean energy carrier for the future energy economy. The preparation of highly efficient catalysts for hydrogen release from FA at room temperature has attracted much attention but still remains a great challenge. Herein, ultrafine bimetallic PdIr nanoparticles (NPs) immobilized by amine-functionalized SBA-15 (PdIr/SBA-15-NH2) have been successfully synthesized via a facile surface functionalization and co-reduction method. The characterized results showed that ultrafine bimetallic PdIr NPs with a small size of around 1.1 nm were highly dispersed on SBA-15-NH2. Among all the as-synthesized catalysts, the optimized Pd0.85Ir0.15/SBA-15-NH2 nanocomposites (NCs) exhibited the highest catalytic activity and 100% H2 selectivity toward the selective dehydrogenation of FA, giving an initial turnover frequency (TOF) value as high as 3087 h−1 at room temperature. To the best of our knowledge, this is the first report showing that the Ir-containing heterogeneous catalyst can achieve a complete dehydrogenation of FA to H2. The excellent catalytic performance of this catalyst might be attributed to the modified electronic effects of Pd with Ir, the ultrafine size and high dispersion of PdIr NPs, and the synergetic interaction between the PdIr NPs and SBA-15-NH2. The amine functional groups of SBA-15-NH2 not only can lead to ultrafine and well-dispersed PdIr NPs and stabilize the PdIr NPs, but also can serve as Bronsted basic sites, which facilitates the O–H bond dissociation of FA and forms a formate intermediate. The present PdIr/SBA-15-NH2 NCs with efficient catalytic effects on the dehydrogenation of FA may greatly promote the practical application of the FA system on fuel cells.

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.

Hydrous hydrazine (N2H4·H2O) is considered a highly promising liquid chemical hydrogen storage material because of its high hydrogen content (8.0 wt%), simple byproduct (i.e., N2) and safe handling. In this work, noble-metal-free NiFe nanoparticles (NPs) supported on nano CeZrO2 solid solutions have been facilely synthesized and successfully applied as a highly efficient catalyst for the rapid and complete decomposition of N2H4 in aqueous solution. The turnover frequency (TOF) value of the NiFe/CeZrO2 catalyst for hydrogen generation from N2H4 reached 119.2 h−1 under alkaline conditions at 343 K, which is 28-fold higher than that of the benchmark catalyst, pure NiFe NPs (4.2 h−1). Moreover, the H2 selectivity and activity show almost no decrease after five runs, indicating that the prepared NiFe/CeZrO2 catalyst possesses high durability and stability under the current conditions. The high catalytic performance can be attributed to the synergistic electronic effect between NiFe NPs and nano CeZrO2 solid solutions, as well as small nanoparticles with highly dispersed active sites.

The efficient and selective dehydrogenation of formic acid by a robust solid catalyst at room temperature is highly attractive for a fuel cell-based hydrogen economy but still very challenging. Although significant progress has been achieved in the development of heterogeneous catalysts, their catalytic performance remains inadequate. Herein, we report a facile and surfactant-free method for the anchoring of the PdAg-CeO2 nanocomposite (3.6 nm in diameter) onto mesoporous carbon (denoted as PdAg-CeO2/MC). The optimized PdAg-CeO2/MC catalyst exhibited an exceedingly high catalytic activity (turnover frequency, 2272.8 h−1 at 303 K and 5275.5 h−1 at 333 K) with a 100% hydrogen selectivity, among the highest catalytic performances reported to date for all heterogeneous catalysts for formic acid dehydrogenation. Systematic studies indicated that strong synergistic interactions between PdAg-CeO2 nanocomposites and the MC host were realized due to the presence of amorphous CeO2 with abundant oxygen vacancies for coordination; the excellent catalytic results indicated more possibilities for the effective application of formic acid as a promising hydrogen storage material.

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.

Hydrous hydrazine (N2H4·H2O) is considered to be a promising chemical hydrogen storage carrier due to its high hydrogen content (8.0 wt%), production of only N2 in addition to H2, and facile recharging as a stable liquid. In this work, for the first time, CoPt NPs supported on La(OH)3 are used as a highly effective catalyst for selective decomposition of N2H4. Surprisingly, the La(OH)3 nanosheet-supported CoPt NPs exhibit superior catalytic performance, releasing 3 equiv. (H2 + N2) with turnover frequency (TOF) values of up to 734.2 h−1 at 303 K and 2400 h−1 at 323 K; these are higher than those of most reported catalysts for the dehydrogenation of N2H4. Especially, CoPt/La(OH)3 can be easily separated from the reaction solution using a magnet due to its super-paramagnetic nature, and it can maintain its high activity and 100% selectivity even after five cycles. The high performance of CoPt/La(OH)3 can be attributed to the electronic interaction between Co and Pt, strong basic sites on the surface of La(OH)3 and a synergistic cooperative effect between the ultrafine CoPt NPs and the La(OH)3 support. The development of a high performance Co-based catalyst may promote the effective application of hydrous hydrazine as a promising hydrogen storage material.

Designing highly efficient catalysts for use in fuel production is a highly attractive research area but still remains challenging. Herein, for the first time, ultrafine Ni nanoparticles (NPs) self-assembled on ceria nanowires (NWs) and then embedded in a microporous silica shell (denoted as Ni-CeO

Hydrogen (H

Development of low-cost and high-performance catalysts for hydrogen generation via hydrolysis of ammonia borane (NH3BH3, AB) is a highly desirable pathway for future hydrogen utilization. In this work, Ni nanocatalysts doped with CeOx and supported on graphene (Ni-CeOx/graphene) were synthesized via a facile chemical reduction route and applied as robust catalysts for the hydrolysis of AB in aqueous solution at room temperature. The as-synthesized Ni-CeOx/graphene nanocomposites (NCs) exhibited excellent catalytic activity with a turnover frequency (TOF) as high as 68.2 min−1, which is 49-fold higher than that for a simple Ni nanoparticle catalyst and is among the highest values reported for non-noble metal catalysts in AB hydrolysis. The development of efficient and low-cost Ni-CeOx/graphene catalysts enhances the feasibility of using ammonia borane as a chemical hydrogen storage material, which may find application ina hydrogen fuel-cell based economy.

Trimetallic NiFePd nanoparticles (NPs) anchored on metal-organic framework (MOF) MIL-101 have been facilely prepared via a simple impregnation method. The as-prepared NiFePd/MIL-101 catalysts have been characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) equipped with energy dispersed X-ray detector (EDX) and selected area electron diffraction (SAED), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), N2 adsorption/desorption isotherms and X-ray photoelectron spectroscopy (XPS) techniques. And the as-synthesized catalysts have been applied for hydrogen generation from aqueous alkaline solution of hydrazine borane (HB, N2H4BH3). Compared to the pure Ni0.36Fe0.24Pd0.4 NPs, MIL-101 supported mono- and bi-metallic counterparts, the Ni0.36Fe0.24Pd0.4/MIL-101 catalyst exhibits much higher catalytic performance for complete conversion of N2H4BH3 to H2 with 100% selectivity at 323 K. The turnover frequency (TOF) value for the dehydrogenation of N2H4BH3 in the presence of Ni0.36Fe0.24Pd0.4/MIL-101 catalyst reaches 60 h−1. Remarkably, the Ni0.36Fe0.24Pd0.4/MIL-101 catalyst also shows high catalytic activity and 100% selectivity towards hydrogen generation from hydrous hydrazine (N2H4·H2O) at 323 K with a TOF value of 40.8 h−1. In addition, the durability tests exhibit that the Ni0.36Fe0.24Pd0.4/MIL-101 catalyst is still highly active in the complete dehydrogenation of N2H4BH3 and decomposition of N2H4·H2O with 100% hydrogen selectivity even after five recycles.

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.

Hydrazine borane (N2H4BH3, 15.4 wt% H) has been considered as a highly promising hydrogen storage material because of its inherent advantages such as high hydrogen content and high stability in the solid state. However, the practical application of N2H4BH3 for the generation of hydrogen is strongly inhibited by the need for expensive noble metal-based catalysts. To overcome this challenge, noble-metal-free CuNiMo nanocatalysts were prepared using a facile chemical reduction approach under an ambient atmosphere at room temperature. Unexpectedly, the resultant CuNiMo catalyst exhibits excellent catalytic activity, and 100% H2 selectivity toward hydrogen generation from N2H4BH3via its BH3 group hydrolysis and N2H4 moiety decomposition at 323 K. To the best of our knowledge, this is the first report of a noble-metal-free catalyst achieving a complete conversion of N2H4BH3 to H2. In addition, CuNiMo can achieve a complete dehydrogenation of hydrous hydrazine (N2H4·H2O). The excellent catalytic performance of the Cu0.4Ni0.6Mo catalyst may be attributed to the electronic modification among Cu, Ni and Mo, and may also be related to the strong basic sites of Cu0.4Ni0.6Mo. The present simple, low cost, highly efficient, and highly selective catalyst may promote the practical application of N2H4BH3 as an effective hydrogen storage material.

Cr2O3 doped NiM (M = Pt, Rh, and Ir) hybrid nanoparticles are successfully fabricated via a co-reduction route at room temperature. It is found that the addition of Cr2O3 not only reduces the size of the bimetallic nanoparticles and significantly increases the BET surface area as compared to that of pure Ni0.9Pt0.1 nanoparticles, but also increases the electron density of NiPt, resulting in significantly enhanced catalytic activity. The Ni0.9Pt0.1-Cr2O3 hybrid nanoparticles exhibit high catalytic activity for the dehydrogenation of hydrazine borane with a turnover frequency value of 1200 h−1 at 50 °C, which is 20 times higher than that of pure Ni0.9Pt0.1 nanoparticles and even surpasses those of most of the reported heterogeneous catalysts. The catalytic performance and H2 selectivity of NiM (M = Pt, Rh, Ir) nanoparticles are also significantly improved by the dopant Cr2O3. Other metal oxides MOx (M = Mo, W and Mn) enhance the activity of the NiPt nanoparticles as well. Our study provides a general approach for the preparation of NiM/metal-oxide hybrid nanoparticles as a type of highly efficient catalyst for the complete dehydrogenation of hydrazine borane, ammonia borane and hydrazine.

Metal–organic framework (MOF) immobilized Rh–Ni alloy nanoparticles (NPs) with a mean size of 2.8 nm have been facilely and successfully fabricated via a reduction rate controlled method. Bimetallic NP/MOF composites with uniform tiny RhNi alloy NPs immobilized on MOFs, high surface areas (1970 m2 g−1), and accessible porous structure have been obtained. The resulting RhNi/MOF catalysts show high catalytic activity and robust durability for complete H2 evolution from hydrazine borane (N2H4BH3) and hydrous hydrazine (N2H4·H2O). The optimized Rh0.8Ni0.2/MIL-101 catalyst exhibits excellent catalytic performance for the dehydrogenation of N2H4BH3 and N2H4·H2O in aqueous solution with 100% conversion and hydrogen selectivity, high total turnover frequencies (TOF), up to 1200 and 428.6 mol(H2) mol(Rh+Ni)−1 h−1, respectively, the highest over Rh-based catalysts. The high activity and prominent durability of Rh0.8Ni0.2/MIL-101 are highly dependent on the features of the MOF immobilized tiny RhNi alloy NPs, the strong interaction between the MOF crystal and RhNi alloy NPs, the optimized surface and electronic structure of RhNi alloy with an atomic ratio of 8 : 2, and the accessible open porous structure for free mass transfer.

In this work, a series of Ni 1-x M x (M = Cr, Mo, W) nanoparticles (NPs) have been successfully synthesized via a simple surfactant-aided co-reduction method and employed as highly efficient and cost effective catalysts for hydrogen generation from aqueous solution of ammonia borane (NH 3 BH 3 , AB) at room temperature. It is found that the as-synthesized NiM NPs (M = Cr, Mo, W) exhibit much higher catalytic performance for the hydrolysis of AB as compared to that of pure Ni NPs. In addition, among all the Ni 1-x M x (M = Cr, Mo, W) NPs, the Ni 0.9 Cr 0.1 , Ni 0.9 Mo 0.1 , and Ni 0.8 W 0.2 NPs show the highest catalytic activities with the turnover frequency (TOF) values of 10.7, 27.3 and 25.0 mol H 2 (mol metal min) −1 , respectively. Remarkably, these optimized NiM catalysts can also perform efficiently in the hydrolysis of hydrazine borane (N 2 H 4 BH 3 , HB). The present low-cost and high-performance of the NiM catalysts system may encourage the practical application of AB and HB as the promising chemical hydrogen storage materials.

Bimetallic Rh–Ni nanoparticles (NPs) immobilized on the cerium hydroxide carbonate (Ce(OH)CO3) have been successfully prepared by a facile co-reduction route, and characterized by XRD, SEM, TEM, EDX, ICP, XPS, and TG-DTA. The as-synthesized Rh–Ni/Ce(OH)CO3 nanocomposites (NCs) with different metal compositions were applied as the highly efficient catalysts for hydrogen generation from the alkaline solution of hydrazine (N2H4). Especially, the Rh55Ni45/Ce(OH)CO3 NCs exerted the highly activity and 100% H2 selectivity for the decomposition of hydrazine, providing high turnover frequency (TOF) values of 150 h−1 at 30 °C and 395 h−1 at 50 °C, respectively, relative high values for the metal catalysts. The activation energy for the decomposition of hydrazine catalyzed by Rh55Ni45/Ce(OH)CO3 NCs was measured to be 38.8 kJ/mol, lower than most of the values reported for this reaction using many different catalysts. This excellent catalytic performance could be attributed to not only the strain and ligand effects between Rh and Ni, but also the strong interaction between RhNi NPs and Ce(OH)CO3 support. Such a highly catalyst may greatly encourage the practical application of hydrazine as a hydrogen storage material.

Ni nanoparticles modified with a Mo dopant have been synthesized on graphene sheets via a facile chemical reduction route, which show the highest catalytic activity reported to date for noble-metal-free catalysts for hydrogen evolution from the hydrolysis of ammonia borane with a turnover frequency value as high as 66.7 mol H2 (mol metal min)−1.

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%.

The development of highly active, stable, and inexpensive catalysts for efficient and complete dehydrogenation of hydrazine is highly attractive but still very challenging. Herein, Cr2O3-modified NiFe (NiFe-Cr2O3) nanopartciles (NPs) have been designed as the heterogeneous catalyst. Both the catalytic activity and hydrogen selectivity of Ni0.9Fe0.1-Cr2O3 NPs were improved remarkably as compared with those of their mono-metallic counterparts. The prepared Ni0.9Fe0.1-Cr2O3 catalyst exhibited an outstanding catalytic activity to release 3.0 equiv. (H2 + N2) from hydrazine in only 8.5 min at 70 °C, providing a turnover frequency (TOF) value of 893.5 h−1 based on surface metal atoms. Systematic studies indicated that the small size and high surface area of Ni0.9Fe0.1-Cr2O3 as well as the strong synergistic electronic effect between Cr2O3 and NiFe NPs resulted in the excellent activity of Ni0.9Fe0.1-Cr2O3 catalyst. Such a highly rapid, long term durability, and low cost catalyst may encourage greatly the practical application of hydrous hydrazine as a chemical hydrogen storage material.

Ultrafine non-noble bimetallic Cu–Co nanoparticles (∼2 nm) encapsulated within SiO2 nanospheres (Cu–Co@SiO2) have been successfully synthesized via a one-pot synthetic route in a reverse micelle system and characterized by SEM, TEM, EDS, XPS, PXRD, ICP, and N2 adsorption–desorption methods. In each core–shell Cu–Co@SiO2 nanosphere, several Cu–Co NPs are separately embedded in SiO2. Compared with their monometallic counterparts, the bimetallic core–shell nanospheres CuxCo1–x@SiO2 with different metal compositions show a higher catalytic performance for hydrogen generation from the hydrolysis of ammonia borane (NH3BH3, AB) at room temperature, due to the strain and ligand effects on the modification of the surface electronic structure and chemical properties of Cu–Co NPs in the SiO2 nanospheres. Especially, the Cu0.5Co0.5@SiO2 nanospheres show the best catalytic performance among all the synthesized CuxCo1–x@SiO2 catalysts in the hydrolytic dehydrogenation of AB. In addition, the activation energy (Ea) of C...

CeOx-modified RhNi nanoparticles (NPs) grown on reduced graphene oxide (rGO) (RhNi@CeOx/rGO) have been facilely prepared and successfully used as highly efficient catalysts for the rapid and complete hydrogen generation from aqueous solution of hydrazine borane (N2H4BH3) and hydrazine (N2H4), respectively. It was found that the CeOx-doped RhNi NPs with a size of around 3.5 nm were highly dispersed on rGO nanosheets. Among all the catalysts investigated, the optimized catalyst Rh0.8Ni0.2@CeOx/rGO with a CeOx content of 13.9 mol% exhibited the highest catalytic performance. The total turnover frequency (TOF) of Rh0.8Ni0.2@CeOx/rGO for hydrogen generation from N2H4BH3 reached 666.7 h−1 (molH2 mol(Rh+Ni)−1 h−1) at 323 K, which was among the highest of all the catalysts reported to date for this reaction, 10-fold higher than that of the benchmark catalyst Rh0.8Ni0.2, and 3-fold higher than that of Rh0.8Ni0.2 with a CeOx dopant (Rh0.8Ni0.2@CeOx) and a rGO support (Rh0.8Ni0.2/rGO). Even at room temperature, Rh0.8Ni0.2@CeOx/rGO can achieve a complete hydrogen generation from N2H4BH3 and N2H4 with a TOF value of 111.2 and 36.4 h−1. This excellent catalytic performance might be attributed to the synergistic structural and electronic effects of the RhNi NPs, CeOx dopant, and rGO support. Moreover, this general method can be easily extended to facile synthesis of other metal/rGO systems with the doping of rare-earth oxides for more applications.

The catalytic dehydrogenation of hydrazine borane (N2H4BH3) and hydrous hydrazine (N2H4·H2O) for H2 evolution is considered as two of the pivotal reactions for the implementation of the hydrogen-based economy. A reduction rate controlled strategy is successfully applied for the encapsulating of uniform tiny NiPt alloy nanoclusters within the opening porous channels of MOFs in this work. The resultant Ni0.9Pt0.1/MOF core–shell composite with a low Pt content exerted exceedingly high activity and durability for complete H2 evolution (100% hydrogen selectivity) from alkaline N2H4BH3 and N2H4·H2O solution. The features of small NiPt alloy NPs, strong synergistic effect between NiPt alloy NPs and the MOF, and open pore structure for freely mass transfer made NiPt/MIL-101 an excellent catalyst for highly efficient H2 evolution from N2H4BH3 or N2H4·H2O.

Ru@SiO2 core shell structured nanospheres have been prepared via a one-pot synthetic route in a NP-5/cyclohexane reverse micelle system and characterized by XRD, SEM, TEM, N-2 adsorption-desorption, and H-2 temperature programmed desorption. The characterized results show that ultrafine Ru nanoparticles (NPs) of around 2 nm are effectively embedded in the center of well-proportioned spherical and porous silica nanospheres (25 nm in diameter). Interestingly, the number of Ru NPs increases inside the spherical particles of SiO2 as the increase of Ru loading. The as-synthesized Ru@SiO2 exhibits high catalytic activity and good durability for hydrogen generation from the aqueous of ammonia borane (AB) complex under ambient atmosphere at room temperature. The hydrolysis activation energy of Ru@SiO2 was estimated to be about 38.2 kJ mol(-1), which is lower than most of the reported activation energy values for the same reaction using many different Ru-based and other noble metal containing catalysts, indicating the superior catalytic performance of these core shell structured nanospheres. (C) 2014 Elsevier B.V. All rights reserved.

In this work, a series of new Cu 1− x Fe x alloy nanoparticles (NPs) have been successfully in situ synthesized by a very simple method and used as catalysts for hydrogen generation from the aqueous solution of ammonia borane (AB) under ambient atmosphere at room temperature. The prepared nanoalloys exhibit excellent catalytic activity, especially for Cu 0.33 Fe 0.67 sample outperform the activity of monometallic counterparts, and even of Cu@Fe core–shell NPs. By using an external magnet, these catalysts can be readily separated from the solution for recycle purpose, and can keep the high activity even after 8 times of recycle under ambient atmosphere. The hydrolysis activation energy for the Cu 0.33 Fe 0.67 alloy NPs was measured to be approximately 43.2 kJ/mol, which is lower than most of the reported activation energy values for the same reaction using many different catalysts except for some noble-metal containing catalysts, indicating the superior catalytic performance of Cu 0.33 Fe 0.67 nanocatalysts.

Highly dispersed Pt-CeO2 hybrids arched on reduced graphene oxide (Pt-CeO2 /rGO) were facilely synthesized by a combination of the reverse micelle technique and a redox reaction without any additional reductant or surfactant. Under a N2 atmosphere, the redox reaction between Ce3+ and Pt2+ occurs automatically in alkaline solution, which results in the formation of Pt-CeO2 /rGO nanocomposites (NCs). The as-synthesized Pt-CeO2 /rGO NCs exhibit superior catalytic performance relative to that shown by the free Pt nanoparticles, Pt/rGO, Pt-CeO2 hybrid, and the physical mixture of Pt-CeO2 and rGO; furthermore, the nanocomposites show significantly better activity than the commercial Pt/C catalyst toward the hydrolysis of ammonia borane (NH3 BH3 ) at room temperature. Moreover, the Pt-CeO2 /rGO NCs have remarkable stability, and 92 % of their initial catalytic activity is preserved even after 10 runs. The excellent activity of the Pt-CeO2 /rGO NCs can be attributed not only to the synergistic structure but also to the electronic effects of the Pt-CeO2 /rGO NCs among Pt, CeO2 , and rGO.

Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)−1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol−1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively.