Abstract
The design of cost-effective and competent electrochemical water splitting module that is functional in a wide pH range is still a formidable challenge for viable H2 production. Herein, we report control synthesis of Ni/Ni3C nanoparticles (NPs) induced engineering of the nitrogen-enriched carbon-nanotubes (NCNT) of three different sizes/morphologies by the pyrolysis of melamine with Ni(NO3)·6H2O at various stoichiometric ratios (0.5-wt%, 2-wt% and 4-wt% of Ni). The catalytic potential and structural integrity of the in-situ self-assembled hybrid material was explored and found very effective to catalyse both OER and HER in a broad pH range (0-14). Promisingly, the nanostructuring of the Ni/Ni3C NPs and subsequently the diameter of the NCNT hold the catalytic potential, where 0.5-Ni/Ni3C@NCNT (average size ≈ 15–20 nm) showed remarkable activity for OER (ƞ10-base/acid/neutral = 280/400/600 mV, Tafel slopebase = 42 mV/dec) and HER (ƞ10-acid/base/neutral = 210/290/370 mV, Tafel slopeacid = 40 mV/dec). It is anticipated, that favourable electronic modulation of Ni/Ni3C, structural strain of NCNT, and possible concerted synergistic effect of the hybrid/doped nanocarbons with metal-carbide hold a great potential in this regard, and such modular strategies tailoring the structural-performance relationship may provide the guidance towards the designing of commercially viable electrocatalysts in this regard.
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•Ni/Ni3C nanoparticles induced engineering of the N-enriched carbon nanotubes (CNT).•Ni/Ni3C NPs – CNT composites are highly effective bifunctional electrocatalysts both for OER and HER in a wide pH range.•The diameter of Ni/Ni3C NPs and CNT plays a key role to control electrochemical parameters for OER and HER.