Pd-CNT-SiO2 nanoskein: composite structure design for formic acid dehydrogenation

Bimetallic PdCo Nanoparticles Loaded in Amine Modified Polyacrylonitrile Hollow Spheres as Efficient Catalysts for Formic Acid Dehydrogenation

Polyacrylonitrile hollow nanospheres (HPAN), derived from the polymerization of acrylonitrile in the presence of polystyrene emulsion (as template), were modified by surface amination with ethylenediamine (EDA), and then used as support for loading Pd or PdCo nanoparticles (NPs). The resultant bimetallic catalyst (named PdCo0.2/EDA-HPAN) can efficiently catalyze the additive-free dehydrogenation of formic acid with very high activity, selectivity and recyclability, showing turnover frequencies (TOF) of 4990 h−1 at 333 K and 915 h−1 at 303 K, respectively. The abundant surface amino groups and cyano group as well as the hollow structure of the support offer a suitable environment for achieving high dispersion of the Pd-based NPs on the surface of EDA-HPAN, thus generating ultra-small bimetallic NPs (bellow 1.0 nm) with high stability. The addition of a small portion of Co may adjust the electronic state of Pd species to a certain extent, which can further improve their capability for the dehydrogenation of formic acid. In addition, the surface amino groups may also play an important role in synergistically activating formic acid to generate formate, thus leading to efficient conversion of formic acid to hydrogen at mild conditions.

Photocatalytic selective H2release from formic acid enabled by CO2captured carbon nitride

The selective decomposition of formic acid (FA) traditionally needs to be carried out under high temperature with the noble metal-based catalysts. Meanwhile, it also encounters a separation of H₂and CO₂for pure H₂production. The photocatalytic FA dehydrogenation under mild conditions can meet a growing demand for sustainable H₂generation. Here, we reported a photocatalytic selective H₂release from FA decomposition at low temperature for pure H₂production by Pt/g-C₃N₄. Low-cost and easy-to-obtained urea was utilized to produce carbon nitride as the metal-free semiconductor photocatalyst, along with a photodeposition to obtain Pt/g-C₃N₄. The electrochemical evidences clearly demonstrate the photocatalytic activity of Pt/g-C₃N₄to produce H₂and CO₂in one-step FA decomposition. And, the impedance is the lowest under simulated solar light of 70 mW cm^-2with a faster electron transfer kinetic. Under simulated solar light, H₂production rate is up to 1.59 mmol · h^-1· g^-1for FA with concentration at 2.65 mol l^-1, 1700 000 times larger than that under visible light and 1928 times under ultraviolet (UV) light. DFT calculations further elucidate that nitrogen (N) active site at the g-C₃N₄has an excellent adsorption towards CO₂molecule capture. Then, H₂molecules are selectively released to simultaneously separate H₂and CO₂in solution. Platinum (Pt) at Pt/g-C₃N₄as the catalytic site contributes into the acceleration of H₂production.

Recent developments of nanocatalyzed liquid-phase hydrogen generation

Hydrogen is the most effective and sustainable carrier of clean energy, and liquid-phase hydrogen storage materials with high hydrogen content, reversibility and good dehydrogenation kinetics are promising in view of "hydrogen economy". Efficient, low-cost, safe and selective hydrogen generation from chemical storage materials remains challenging, however. In this Review article, an overview of the recent achievements is provided, addressing the topic of nanocatalysis of hydrogen production from liquid-phase hydrogen storage materials including metal-boron hydrides, borane-nitrogen compounds, and liquid organic hydrides. The state-of-the-art catalysts range from high-performance nanocatalysts based on noble and non-noble metal nanoparticles (NPs) to emerging single-atom catalysts. Key aspects that are discussed include insights into the dehydrogenation mechanisms, regenerations from the spent liquid chemical hydrides, and tandem reactions using the in situ generated hydrogen. Finally, challenges, perspectives, and research directions for this area are envisaged.