Cu_xCo_1−xO Nanoparticles on Graphene Oxide as A Synergistic Catalyst for High‐Efficiency Hydrolysis of Ammonia–Borane

Abstract

Ammonia-borane (AB) is an excellent material for chemical storage of hydrogen. However,t he practical utilization of AB for production of hydrogen is hindered by the need of expensive noble metal-based catalysts.H ere,w er eport Cu x Co 1Àx Onanoparticles (NPs) facilely deposited on graphene oxide (GO) as alow-cost and high-performance catalyst for the hydrolysis of AB.T his hybrid catalyst exhibits an initial total turnover frequency (TOF) value of 70.0 (H 2 )m ol/(Cat-metal) mol·min, which is the highest TOFe ver reported for noble metal-free catalysts,and agood stability keeping 94 %activity after 5c ycles.S ynchrotron radiation-based X-ray absorption spectroscopy( XAS) investigations suggested that the high catalytic performance could be attributed to the interfacial interaction between Cu x Co 1Àx ON Ps and GO.M oreover,t he catalytic hydrolysis mechanismw as studied by in situ XAS experiments for the first time,w hichr eveal asignificant water adsorption on the catalyst and clearly confirm the interaction between AB and the catalyst during hydrolysis.Controlled storage and release of hydrogen are well-known challenges in establishing av iable fuel-cell-based hydrogen economy. [1][2][3] Recently,the chemical storage of hydrogen was considered as af easible way for practical applications. [1][2][3][4][5][6][7][8] Among the chemical hydrogen-storage materials,a mmoniaborane (AB) has been regarded as aleading contender owing to its high hydrogen content (19.6 wt %), high stability in both aqueous solutions and air at room temperature,a nd nontoxicity. [1][2][3][4][5][6][7][8][9] However,u ntil now,e ffective catalysts for the hydrolysis of AB are typically based on expensive and rare noble metals (such as Pt, Ru), [4,7,8] which has largely hampered applications. [3,5,7] Thus,a lternate catalysts for high-efficiencyh ydrolysis of AB based on inexpensive nonnoble metal elements are highly required and intensely studied. [3,5,7] Despite many catalysts for the hydrolysis of AB,h igh-performance noble metal-free catalyst with practical efficiency and sustainability remains unavailable and adaunting challenge.T he catalytic mechanism regarding the electronic structure changes of the catalysts is also unclear and has largely limited the design of high-efficiencycatalysts.Graphene is an outstanding supporting material for efficient catalysts,b ecause it can enhance the catalytic performance with synergetic effects. [10][11][12][13][14][15][16][17][18] Recently,g raphene was used to support various non-noble metal nanoparticles (NPs) for efficient catalysts for the hydrolysis of AB. [14][15][16] Although the hybrids showed enhanced catalytic properties, their performance remained insufficient and their electronic structure had not been well studied. [14][15][16] Herein we report af acile way to prepare the hybrids of Cu x Co 1Àx ON Ps on graphene oxide (GO). Theo ptimized hybrid (Cu x Co 1Àx O-GO) shows superior catalytic performance in the hydrolysis of AB with ah igh initial TOF value of 70.0 (H 2 )m ol/(Catmetal) mol...

Selective CO2‐to‐CH4 Photoconversion in Aqueous Solutions Catalyzed by Atomically Dispersed Copper Sites Anchored on Ultrathin Graphdiyne Oxide Nanosheets

“…Figure 3d reveals that the oxidized state of Cu in the Cu 2+ /GDYO nanosheets is consistent with the Cu 2+ ions in Cu(NO 3 ) 2 . [ 46 ] However, the Cu L ‐edge shifts to higher photon energies, further confirming that Cu 2+ ions receive electrons from the GDYO nanosheets.…”

Synthesis of a binary alloy nanoparticle catalyst with an immiscible combination of Rh and Cu assisted by hydrogen spillover on a TiO2 support

“…Feng et al observed changes of the Cu state during AB hydrolysis using in situ XAFS, which showed that AB molecules interact with the catalyst rstly and water can approach both the catalyst and AB to attack the N-B bond. 61 Peng et al demonstrated the plausible AB hydrolysis mechanism using DFT calculations. 57 Thus, we show the possible mechanism of AB hydrolysis in Fig.…”

Operando Analyses of Highly Enhanced Water Splitting by Electronically Modulated Non-noble Metal Carbides

“…When Ni in +2 oxidation state substitutes W or Mo (in +4 oxidation state) in the carbide lattice, 81 an incumbent need to maintain the charge balance can trigger the Mo and W to attain a higher partial oxidation state, as observed from the XPS ( Figure S4a, b, S4b) and XANES spectra ( Figure S19a-b). XANES measurements at the Ni (K-edge, 8.33 keV), Mo (K-edge, 19.99 keV) and W (LIII edge, 10.207 keV) edges ( Figure S19a, S19b, and Figure 6) show a prominent increase in the white line intensity of the Mo/W centres upon Ni substitution ( Figure S19a, S19b) which is indicative of the increase in unoccupied states of the d-orbitals., 43,82 Interestingly, the Mo edge shows the appearance of an edge peak ( Figure S19b), corresponding to an 1s → 4 transition, presumably arising from a breaking in symmetry around the local coordination of Mo centres upon Ni substitution. The possibility of charge transfer between the electronically linked Ni & W/Mo ions is expected to optimize the electrochemical adsorption desorption processes resulting in enhanced electrocatalytic activity.…”