Defect‐Rich Co−CoO_x‐Graphene Nanocatalysts for Efficient Hydrogen Production from Ammonia Borane

Abstract

Chemical hydrogen storage ammonia borane has attracted extensive attention as a method of efficient utilization of hydrogen energy. The high-efficiency catalysts are the main factor restricting the hydrogen production of ammonia borane. In this paper, the synergistic effect of Co and CoO x supported on graphene (named CoÀ CoO x @GO-II) promotes the efficient hydrogen production of ammonia borane, and its catalytic hydrogen production rate can reach 5813 mL min À 1 g Co À 1 at 298 K, the corresponding TOF is 15.33 min À 1. After five stability tests, CoÀ CoO x @GO-II maintained 65% of its original catalytic performance. The synergy of metal and metal oxide and the defects in the atomic arrangement ensure the catalytic activity, the large specific surface area of graphene ensures the dispersion and fixation. This strategy may provide a possibility to design highperformance transition metal catalysts.

The Hydrogen‐Storage Challenge: Nanoparticles for Metal‐Catalyzed Ammonia Borane Dehydrogenation

“…180 Thus, the specific surface area of the acid-etched catalyst increased from 72 m 2 g -1 (Co/Cu) to 175 m 2 g -1 (SCo/Cu), and the particle average size decreased from ca 16.2 nm to 6.7 nm, while experimental measured εd value shifted to −3.90 eV and TOF reached 5.7 min -1 in a 198% increase. A recent promising approach for innovative nanocomposites exploitation in hydrolytic AB dehydrogenation is the synthesis of oxides, 181,182 phosphides, 183,184 and borides, 185 Other oxidized composites have been reported and used as nanocatalysts for AB hydrolytic dehydrogenation at 25 °C, notably defect-rich Co-CoOx@graphene (Co material was not completely oxidized), 182 and Co-Co 3 O 4 @carbon dots, 186 188 These catalysts achieved for AB hydrolysis a TOF of 129 min -1 at room temperature. The recyclability of these system was tested over five runs with a notable progressive deactivation (25% of original activity at the 5 th run).…”

“…A recent promising approach for innovative nanocomposites exploitation in hydrolytic AB dehydrogenation is the synthesis of oxides, [ 181,182 ] phosphides, [ 183,184 ] and borides, [ 185 ] bi‐ or monometallic cobalt catalysts. Inspired by CuMoO 4 and CoMoO 4 materials, known in the literature as supercapacitor and anode materials for lithium‐ion batteries, and CoCu nanoalloys known as active catalysts for AB hydrolysis, the molybdenum oxide bimetallic Co x Cu 1− x MoO 4 microsphere catalysts were formed from hydrothermal treatment at 165 °C of dispersion of CoCl 2 , CuCl 2 , and molybdic acid into aqueous urea solution.…”

“…Other oxidized composites have been reported and used as nanocatalysts for AB hydrolytic dehydrogenation at 25 °C, notably defect‐rich Co–CoO x @graphene (Co material was not completely oxidized), [ 182 ] and Co–Co 3 O 4 @carbon dots, [ 186 ] which achieved consistent TOF about 15 to 18 min −1 for this reaction. Other high dimension yolk‐shell structured materials Co 3 O 4 @Co 3 O 4 (and copper‐doped derivatives Co x Cu 1− x Co 2 O 4 @Co y Cu 1− y Co 2 O 4 ) were formed as microspheres with typical diameters between 2 to 4 µm by hydrothermal reaction followed by high temperature calcination process.…”

Co-Based Nanoparticles Fabricated on Ni Foams for Efficient Hydrogen Generation from Ammonia Borane

“…Thus, it is speculated that the synergistic effect between Co 0 and CoO x species has optimistic improvement for NH 3 BH 3 hydrolysis. 41 The doped N in the carbon matrix regulates the binding and coordination of Co NPs and carbon to modulate its stability. 22 The graphitic carbon helps incorporate and disperse the active sites to offer high resistance against corrosion, improving the catalytic activity and stability of the catalyst for long-term operations.…”

“…Additionally, the increase in Co 2+ species after NH 3 BH 3 hydrolysis confirms the partial conversion of Co 0 into CoO x during the reaction (Figure S9). Thus, it is speculated that the synergistic effect between Co 0 and CoO x species has optimistic improvement for NH 3 BH 3 hydrolysis …”