One-pot synthesis of graphene hydrogel-anchored cobalt-copper nanoparticles and their catalysis in hydrogen generation from ammonia borane.

Önder Metin,Ibtihel Zaier

doi:10.3906/kim-2107-32

Abstract

We reported a facile one-pot synthesis of bimetallic CoCu nanoparticles (NPs) anchored on graphene hydrogel (GH-CoCu) as catalysts in hydrogen generation from the hydrolysis of ammonia borane (HAB). The presented novel one-pot method composed of the reduction of the mixture of graphene oxide, cobalt(II), and copper(II) acetate tetrahydrates by aqueous ethylene glycol solution in a teflon-coated stainless-steel reactor at 180 °C. The structure of the yielded GH-CoCu nanocatalysts was characterized by TEM, SEM, XRD, XPS, and ICP-MS. This is the first example of both the synthesis of bimetallic CoCu NPs anchored on GH and the testing of a hydrothermally prepared noble metal-free GH-bimetallic nanocomposites as catalysts for the HAB. The presented in situ synthesis protocol allowed us to prepare different metal compositions and investigating their catalysis in the AB hydrolysis, where the best catalytic activity was accomplished by the GH-Co33Cu67 nanocatalysts. The obtained GH-CoCu nanocatalysts exhibited a remarkable catalytic performance in the HAB by providing the highest hydrogen generation rate of 1015.809 ml H2 gcatalyst-1 min-1 at room temperature. This study has a potential to pave a way for the development of other GH-based bimetallic nanocatalysts that could be used in different applications.

Highlights

One of the current global concerns is focused on how to manage the continuously growing energy demand with the existing fossil fuel supplies which are likely to face shortages in the future as well as they are pointed as the origin of the environmental problems.the search for alternative energy sources that might be utilized all over the world regardless of the geographic position has been an attractive research topic
It was reported that the use of graphene-based support materials improves the catalytic activity of CoCu nanocatalysts in the ammonia borane (AB) hydrolysis [53,54,55,56]. When these CoCu-based nanocatalyst systems were examined, it could be seen that they were mostly prepared by using two-step protocol involving the impregnation of metal precursors into the support material followed by chemical reduction using mostly NaBH4 as the reducing agent
The presented one-pot protocol for the synthesis of graphene hydrogel (GH)-CoCu nanocomposites included two simultaneous processes, namely the reduction and the self-assembly of graphene oxide (GO) layers into the GH and the reduction of metal precursors into the metallic NPs supported on the formed GH network (Figure 1)

Summary

Introduction

One of the current global concerns is focused on how to manage the continuously growing energy demand with the existing fossil fuel supplies which are likely to face shortages in the future as well as they are pointed as the origin of the environmental problems. It was reported that the use of graphene-based support materials improves the catalytic activity of CoCu nanocatalysts in the AB hydrolysis [53,54,55,56]. When these CoCu-based nanocatalyst systems were examined, it could be seen that they were mostly prepared by using two-step protocol involving the impregnation of metal precursors into the support material followed by chemical reduction using mostly NaBH4 as the reducing agent. The GH-CoCu nanocatalysts provided a relatively high catalytic activity with the highest hydrogen generation rate of 1015.809 ml H 2 gcatalyst-1 min-1 , which is higher than those of their monometallic counterparts

Materials and methods

Results and discussion

Conclusion

B: Environmental