Reversible, carbon dioxide mediated chemical hydrogen storage was first demonstrated using a heterogeneous Pd catalyst supported on mesoporous graphitic carbon nitride (Pd/mpg-C 3 N 4 ). The Pd nanoparticles were found to be uniformly dispersed onto mpg-C 3 N 4 with an average size of 1.7 nm without any agglomeration and further exhibit superior activity for the dehydrogenation of formic acid with a turnover frequency of 144 h À1 even in the absence of external bases at room temperature. Initial DFT studies suggest that basic sites located at the mpg-C 3 N 4 support play synergetic roles in stabilizing reduced Pd nanoparticles without any surfactant as well as in initiating H 2 -release by deprotonation of formic acid, and these potential interactions were further confirmed by X-ray absorption near edge structure (XANES). Along with dehydrogenation, Pd/mpg-C 3 N 4 also proves to catalyze the regeneration of formic acid via CO 2 hydrogenation. The governing factors of CO 2 hydrogenation are further elucidated to increase the quantity of the desired formic acid with high selectivity.

The electrochemical synthesis of NH 3 by the nitrogen reduction reaction (NRR) at low temperature (<65 °C) and atmospheric pressure using nanosized γ-Fe 2 O 3 electrocatalysts were demonstrated. The activity and selectivity of the catalyst was investigated both in a 0.1 M KOH electrolyte and when incorporated into an anion-exchange membrane electrode assembly (MEA). In a half-reaction experiment conducted in a KOH electrolyte, the γ-Fe 2 O 3 electrode presented a faradaic efficiency of 1.9% and a weight-normalized activity of 12.5 nmol h −1 mg −1 at 0.0 V RHE . However, the selectivity toward N 2 reduction decreased at more negative potentials owing to the competing proton reduction reaction. When the γ-Fe 2 O 3 nanoparticles were coated onto porous carbon paper to form an electrode for a MEA, their weight-normalized activity for N 2 reduction was found to increase dramatically to 55.9 nmol h −1 mg −1 . However, the weight-and area-normalized N 2 reduction activities of γ-Fe 2 O 3 decreased progressively from 35.9 to 14.8 nmol h −1 mg −1 and from 0.105 to 0.043 nmol h −1 cm −2 act , respectively, during a 25 h MEA durability test. In summary, a study of the fundamental behavior and catalytic activity of γ-Fe 2 O 3 nanoparticles in the electrochemical synthesis of NH 3 under low temperature and pressure is presented.

The strong non-nucleophilic base bis(dimethylamino)naphthalene (Proton Sponge, PS) has been found to promote the rate and extent of H(2)-release from ammonia borane (AB) either in the solid state or in ionic-liquid and tetraglyme solutions. For example, AB reactions in 1-butyl-3-methylimidazolium chloride (bmimCl) containing 5.3 mol % PS released 2 equiv of H(2) in 171 min at 85 degrees C and only 9 min at 110 degrees C, whereas comparable reactions without PS required 316 min at 85 degrees C and 20 min at 110 degrees C. Ionic-liquid solvents proved more favorable than tetraglyme since they reduced the formation of undesirable products such as borazine. Solid-state and solution (11)B NMR studies of PS-promoted reactions in progress support a reaction pathway involving initial AB deprotonation to form the H(3)BNH(2)(-) anion. This anion can then initiate AB dehydropolymerization to form branched-chain polyaminoborane polymers. Subsequent chain-branching and dehydrogenation reactions lead ultimately to a cross-linked polyborazylene-type product. AB dehydrogenation by lithium and potassium triethylborohydride was found to produce the stabilized Et(3)BNH(2)BH(3)(-) anion, with the crystallographically determined structure of the [Et(3)BNH(2)BH(3)](-)K(+).18-crown-6 complex showing that, following AB nitrogen-deprotonation by the triethylborohydride, the Lewis-acidic triethylborane group coordinated at the nitrogen. Model studies of the reactions of [Et(3)BNH(2)BH(3)](-)Li(+) with AB show evidence of chain-growth, providing additional support for a PS-promoted AB anionic dehydropolymerization H(2)-release process.

The Ti-based heterogeneous catalysts TiSBA15, Bu cap TiSBA15, TS-1, and [Ti,Al]-MFI were investigated with respect to controlling factors for the competitive decomposition of aqueous H2O2 during selective catalytic oxidations. DRUV–vis spectroscopy revealed that the titanium species in these materials exist mainly in isolated, tetrahedral coordination environments. The observed rates of H2O2 decomposition at 65 °C in acetonitrile decreased in the following order: Bu cap TiSBA15 > TiSBA15 and TS-1 > [Ti,Al]-MFI. The decompositions of H2O2 were also monitored in the presence of inorganic additives and Brønsted acids and bases, in benzene/aqueous biphasic solutions. Significant retardation of the decomposition rates with the KH2PO4 additive was found with TiSBA15, which suggests that the KH2PO4 stabilizer may be useful for optimization of hydrogen peroxide efficiency in catalytic oxidations. DRUV–vis spectroscopy was employed to identify possible catalytically active intermediates, proposed to be Ti(IV)(OOH) species that are produced upon reaction of the Ti-based materials and H2O2. Density Functional Theory (DFT) studies starting from a molecular model, (HO)Ti[OSi(OH)3]3, suggest that three Ti(IV)(OOH) intermediates are in equilibrium, and the formation of Ti–O• and HOO• radical species may be involved in the H2O2 decomposition. In addition, the potential role of KH2PO4 in the H2O2 decomposition process, as a proton acceptor in a [Ti(OO)(HOP(O)(OH)2)] complex, has been investigated.