Two-dimensional mica nanosheets supported Fe nanoparticles for NH3 decomposition to hydrogen

Support Effect of Boron Nitride on the First N-H Bond Activation of NH3 on Ru Clusters

Support effect is an important issue in heterogeneous catalysis, while the explicit role of a catalytic support is often unclear for catalytic reactions. A systematic density functional theory computational study is reported in this paper to elucidate the effect of a model boron nitride (BN) support on the first N-H bond activation step of NH3 on Run (n = 1, 2, 3) metal clusters. Geometry optimizations and energy calculations were carried out using density functional theory (DFT) calculation for intermediates and transition states from the starting materials undergoing the N-H activation process. The primary findings are summarized as follows. The involvement of the model BN support does not significantly alter the equilibrium structure of intermediates and transition states in the most favorable pathway (MFP). Moreover, the involvement of BN support decreases the free energy of activation, ΔG≠, thus improving the reaction rate constant. This improvement is more obvious at high temperatures like 673 K than low temperatures like 298 K. The BN support effect leading to the ΔG≠ decrease is most significant for the single Ru atom case among all three cases studied. Finally, the involvement of the model BN may change the spin transition behavior of the reaction system during the N-H bond activation process. All these findings provide a deeper insight into the support effect on the N-H bond activation of NH3 for the supported Ru catalyst in particular and for supported transition metal catalysts in general.

Nickel Nanoparticles Anchored on Activated Attapulgite Clay for Ammonia Decomposition to Hydrogen

Ammonia decomposition to hydrogen technique is an effectively way to solve the problems associated with the storage and transportation of hydrogen, but the development of a high-performance catalyst for ammonia decomposition is a great challenge. Ni species supported on activated attapulgite clay (AATP) is prepared by a homogeneous precipitation method for ammonia decomposition to COx-free H2. The structural properties of the Ni/AATP catalysts are characterized by thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy, H2 temperature-programmed reduction, and N2 sorption technique. It is revealed that the porous structure and high surface area of rod-like symmetric AATP results in highly dispersed NiO particles because the presence of a strong interaction between AATP and NiO particles. In particular, the Si-OH in AATP can react with Ni species, forming Si-O-Ni species at the interface between Ni and AATP. The Ni/AAPT catalysts are used for ammonia decomposition, the 20%-Ni/ATTP catalyst shows a 95.3% NH3 conversion with 31.9 mmol min−1 gcat−1 H2 formation rate at 650 °C. This study opens a new way to utilize natural minerals as an efficient support of catalysts towards ammonia decomposition reaction.

Catalytic ammonia reforming: alternative routes to net-zero-carbon hydrogen and fuel

Ammonia is an energy-dense liquid hydrogen carrier and fuel whose accessible dissociation chemistries offer promising alternatives to hydrogen electrolysis, compression and dispensing at scale. Catalytic ammonia reforming has thus emerged as an area of renewed focus within the ammonia and hydrogen energy research & development communities. However, a majority of studies emphasize the discovery of new catalytic materials and their evaluation under idealized laboratory conditions. This Perspective highlights recent advances in ammonia reforming catalysts and their demonstrations in realistic application scenarios. Key knowledge gaps and technical needs for real reformer devices are emphasized and presented alongside enabling catalyst and reaction engineering fundamentals to spur future investigations into catalytic ammonia reforming.

Noble-metal-free nanocatalysts for hydrogen generation from boron- and nitrogen-based hydrides

We focus on the recent advances in non-noble metal catalyst design, synthesis and applications in dehydrogenation of chemical hydrides (e.g. NaBH₄, NH₃BH₃, NH₃, N₂H₄, N₂H₄BH₃) due to their high hydrogen contents and CO-free H₂ production.

Enhanced Catalysis of Pt3 Clusters Supported on Graphene for N–H Bond Dissociation

We report an in-depth study of catalytic N–H bond dissociation with typical platinum clusters on graphene supports. Among all the pristine graphene- and defective graphene-supported Pt clusters of different sizes that were studied, the Pt 3/G cluster possesses the highest reactivity and lowest activation barriers for each step of N–H dissociation in the decomposition of ammonia. In analyzing the reaction coordinates and projected density of states of the outermost orbitals, we found that the standing triangular Pt 3 on graphene creates prominent Lewis acid/base pair sites, which accommodate the adsorption and subsequent dissociation of *NH x . In comparison, Pt 1 lacks complementary active sites (CAS), causing it to be adverse to nucleophilic reactions, and in contrast, the Pt 13 cluster has weakened interactions and depleted charge density from the support, resulting in the elimination of the CAS effect. A stable pyramid-structured Pt 4 also develops Lewis acid/base sites, especially on defective graphene, but the density of states is still lower than the stand-up Pt 3/G. These findings strongly demonstrate the importance and necessity of cluster active sites for catalytic reactions of polar molecules, novel three-atoms metal cluster catalysis, and the selectivity and catalytic performance in the designing of ammonia fuel cells.