Heterostructured Ni₂Co Layered Double Hydroxide/Reduced Graphene Oxide Nanosheets for H₂ Production Assisted by Benzylamine Oxidation

Abstract

Hybrid water electrolyzers that use facile organic oxidation reactions (OOR) as an alternative to the sluggish oxygen evolution reaction (OER) are projected as high-value electrolyzers due to the simultaneous production of H 2 and value-added chemicals.In the present study, electro-oxidative dehydrogenation of benzylamine (BAm) to benzonitrile (BN) is carried out as an alternate oxidation reaction to OER, coupled with the hydrogen evolution reaction (HER), in a hybrid water electrolysis system. For this, heterostructures of Ni 2 Co layered double hydroxide (LDH) and reduced graphene oxide (rGO) are synthesized by using flocculation of oppositely surface-charged nanosheets and used for the benzylamine oxidation reaction (BAmOR). The Ni 2 Co-LDH/rGO heterostructures require 1.35 V vs RHE to achieve a current density of 10 mA cm −2 in the presence of BAm, compared to 1.61 V vs RHE without BAm, indicating that BAmOR can be a potential alternate to OER. Upon utilizing Ni 2 Co-LDH/rGO heterostructures as the anode and commercial Pt as the cathode in a hybrid water splitting cell, faradaic efficiencies of ∼94% and ∼85% are achieved for H 2 and BN production, respectively. Additionally, the hybrid electrolysis cell is capable of producing 38.6 μmol cm −2 h −1 H 2 even at a cell voltage of 1.39 V, whereas the traditional water electrolysis cell requires a cell voltage of 1.68 V to yield a similar (34.7 μmol cm −2 h −1 ) amount of H 2 . This clearly suggests that substituting the OER with BAmOR is beneficial for not only achieving high efficiency in H 2 production but also producing valueadded BN.