Hollow Nickel–Cobalt Layered Double Hydroxide Supported Palladium Catalysts with Superior Hydrogen Evolution Activity for Hydrolysis of Ammonia Borane

Abstract

Although ammonia borane (NH 3 BH 3 ,A B) has been identified as an excellent hydrogen-storage medium, the development of a highly active catalystt hat can function under mild conditions for controllable hydrogen release is still ag reat challenge. The synergistic effect induced by interactions between metal nanoparticles and asupport has been widely applied in thermocatalytic conversion processes. In this work, Pd nanoparticles (NPs) highly dispersed on hollow NiCol ayered double hydroxide (LDH) wered esigned for efficient hydrogen generation from AB at room temperature. During the hydrolytic dehydrogenation of AB, Pd/a-LDH and Pd/b-LDHe xhibited catalytic activities with total turnover frequency (TOF) values of 49.5 and 28.1 min À1 with activation energy (E a )v alues of 20.56 and 37.56 kJ mol À1 ,r espectively,a t2 98 K; thus, these catalysts outperform mostP d-based catalysts. The improved catalytic effect was attributedt ot he controllable size and fine distribution of the Pd NPs and the collaborative effect provided by the hydroxide of a-LDH and the intercalated anions( HO À ). This catalysts design principle can be easily transferred to other catalyst research fields for energy-conversion and -storage purposes.Hydrogen is the simplest and cleanest fuel carrier and is usually utilized in af uel-cell setup to generate power;i tp roduces only water and heat as byproducts. [1,2] Hydrogenp roduces the highest energy per mass amonga ny fuel. Unfortunately,o wing to its low volumetric density under ambient conditions, the major obstacle that prevents the building of hydrogen economy is the development of advanced storagem ethods that have the potentialf or highere nergy density per volume. [3][4][5] Subsequently,i ti sa lso important to develop technologiest hat can release hydrogen in ac ontrollable fashion under mild conditions from said medium. Chemical hydrides are promising candidates owing to their high gravimetric hydrogen densities and favorable thermodynamic and kinetic properties towards dehydrogenation. [6,7] Among them, ammonia borane (NH 3 BH 3 , AB) is considered to be an efficient carrier,w ith superbstability in aqueous and methanol solutions, ah igh volumetric density of 146 gL À1 ,a nd ah ydrogen capacity of 196 gkg À1 . [8,9] Hydrogen stored in AB can be releasedbyeither thermaldecomposition or solvolysis. [10,11] Considering the high energy input of thermald ecomposition (> 100 8C), much research has been focused on the hydrolytic dehydrogenationo fA B[ Eq. (1)] in the presence of metal catalysts under ambient conditions. [12] Hundreds of metal catalysts have been exploited to promote the efficiency of AB dehydrogenation. [13] Amongt hem, Pd nanoparticle (NP)-based catalytic systems serve as favorable catalysts for the hydrolysiso fA Bb ecause they are cheaper than other precious metals and have higher activity than nonnoble metal catalysts. [14,15] It is well known that although smallsized metal NPs can provide more catalytic active sites, such NPs usuallys uffer from deactivation and inst...

Reusability and stability of a novel ternary (Co–Cd–Fe)-LDH/PbI2 photoelectrocatalytst for solar hydrogen production

“…Figure 12 B illustrates the total impedance (Z) vs. the frequency, whilst Fig. 12 displays the behavior of the phase vs. the logarithm of the frequency and shows a resistive regime related to the R ct at low frequency as well as capacitive contributions related to the C dl of the electrode at high frequencies 50 . From Fig.…”

“…The lifetime of the charge carriers can be estimated from Fig. 12 via the relationship = 1/2π ƒ max 50 . The value of the obtained lifetime of the charge carriers for the T-LDH/PbI 2 NC electrode is estimated to be 7.23 s. The obtained parameters indicate a great reduction in the charge recombination at the electrolyte/electrode interfaces.…”

Photocatalytic H2 Evolution from Ammonia Borane: Improvement of Charge Separation and Directional Charge Transmission

“…The photocatalytic H 2 evolution from ammonia borane in this work in comparison with previous reports. [18,19,[53][54][55][56][57][58][59] The photocatalytic AB hydrogen evolution activity maintained a relatively high level even after runs (Figure 9). The photocatalytic hydrogen evolution activity of Co/CoFeÀ Mo was obviously higher than that of Co/CoFeÀ C during the long time photocatalytic recycle.…”

Hydrogen Production from Ammonia Borane over PtNi Alloy Nanoparticles Immobilized on Graphite Carbon Nitride

“…Tremendous efforts, in the past decades, have been made to explore and design hydrogen storage materials such as hydrazine, formic acid, and ammonia borane and so forth [7][8][9][10][11][12][13]. Among various hydrogen storage materials conducted, ammonia borane (AB), a white solid with excellent → NH 4 BO 2 (aq) + 3H 2 (g).…”