Enhancing Effect of Fe2+ Doping of Ni/NiO Nanocomposite Films on Catalytic Hydrogen Generation

Nickel atoms of nickel foam simultaneously mediated charge redistribution and firm immobilization of zinc oxide for safe and efficient photocatalytic nitrogen oxide removal

Photocatalytic technology has emerged as a promising solution for air purification of ppb-level nitrogen oxides (NOx), but potential risk of secondary pollution should not be overlooked, which could be triggered by the production of toxic intermediate and the potential release of airborne catalyst particles during reaction processes. Herein, nickel foam (NF) has been introduced as not only carrier material but also performance promoter for zinc oxide (ZnO). The NF supported ZnO sample (Ni-ZnO/NF) demonstrates multifunctional superiority: 66.4 % nitric oxide (NO) removal efficiency, <1.7 % nitrogen dioxide (NO2) byproduct generation, and ultralow photocatalyst loss (<1.2 % mass). Mechanistic investigations combining experimental characterization and theoretical simulations reveal atomic substitution processes where NF-derived Ni atoms replace Zn sites in the ZnO lattice, forming stable Ni-O interfacial bonds, which contributes to enhance interaction between ZnO and NF for firm immobilization and form electron localization zones around Ni-O bond for reactants activation and reactive oxygen species formation. The optimized reaction pathway (NO + e- → NO-, NO- + 1O2 → NO3-) ensures complete oxidation while suppressing hazardous intermediates. This work blueprints next-generation supported photocatalysts through atomic-level interface engineering, advancing practical application of photocatalytic technology for sustainable air purification.

Recent Advances and Perspectives on Supported Catalysts for Heterogeneous Hydrogen Production from Ammonia Borane

Ammonia borane (AB), a liquid hydrogen storage material, has attracted increasing attention for hydrogen utilization because of its high hydrogen content. However, the slow kinetics of AB hydrolysis and the indefinite catalytic mechanism remain significant problems for its large-scale practical application. Thus, the development of efficient AB hydrolysis catalysts and the determination of their catalytic mechanisms are significant and urgent. A summary of the preparation process and structural characteristics of various supported catalysts is presented in this paper, including graphite, metal-organic frameworks (MOFs), metal oxides, carbon nitride (CN), molybdenum carbide (MoC), carbon nanotubes (CNTs), boron nitride (h-BN), zeolites, carbon dots (CDs), and metal carbide and nitride (MXene). In addition, the relationship between the electronic structure and catalytic performance is discussed to ascertain the actual active sites in the catalytic process. The mechanism of AB hydrolysis catalysis is systematically discussed, and possible catalytic paths are summarized to provide theoretical considerations for the designing of efficient AB hydrolysis catalysts. Furthermore, three methods for stimulating AB from dehydrogenation by-products and the design of possible hydrogen product-regeneration systems are summarized. Finally, the remaining challenges and future research directions for the effective development of AB catalysts are discussed.

Water State-Driven Catalytic Hydrolysis of Ammonia Borane on Cu3P-Carbon Dot-Cu Composite

Hydrogen production from ammonia borane (AB) is usually governed by water activation, which is not only energy-intensive but also requires expensive and complicated catalysts. We here propose an integrated photocatalytic-photothermal system that dramatically improves water activation and lowers the transport resistance of H₂ by means of intermediate state water evaporation. This system is constructed by covering nanocomposites (Cu₃P-carbon dots-Cu) upon vertically aligned acetate fibers (VAAFs). As a result of superior hydration effect of VAAFs and local photothermal heating for rapid water evaporation, its hydrogen production efficiency from AB hydrolysis reaches over 10 times the particulate suspension system under solar irradiation. Mechanism analysis reveals that the rapid vaporization of intermediate water promotes the cleavages of O-H bonds in bound water and the adsorption reaction of AB and water molecules at active sites. Therefore, this work provides a novel approach to optimize catalytic reaction in thermodynamics and kinetics for the hydrolysis of AB.

Modulating the Acidic Properties of Mesoporous Mox-Ni0.8Cu0.2O Nanowires for Enhanced Catalytic Performance toward the Methanolysis of Ammonia Borane for Hydrogen Production

Rational construction of inexpensive, highly efficient, and stable catalysts for ammonia borane (AB) methanolysis is in high demand but still remains a great challenge. In this work, we have successfully fabricated uniform Mo_x-Ni_0.8Cu_0.2O nanowires using a simple hydrothermal method followed by a post-calcination treatment and flexibly modulated the acidity of their surface by changing the amount of Mo introduced into Ni_0.8Cu_0.2O. The Mo_0.1-Ni_0.8Cu_0.2O catalyst displayed strong catalytic activity toward AB methanolysis with an ultrahigh turnover frequency of 46.9 mol_H2 mol_cat.^-1 min^-1, which is even higher than some noble metal catalysts. In this work, an equation regarding the relationship between the quantity of moderated acid sites of catalysts and its corresponding activity toward AB methanolysis was first determined. A plausible mechanism for AB methanolysis catalyzed by Mo_x-Ni_0.8Cu_0.2O was proposed, and the benefits of the introduction of MoO₃ to Ni_0.8Cu_0.2O for enhancing the catalytic performance were also discussed. These findings can form a basis for the rational construction of inexpensive catalysts with robust performance toward AB methanolysis for hydrogen production.