Bottom-up self-assembly strategy to construct ternary MoxC/Ni3Fe@GL as efficient water splitting electrocatalyst

Abstract

Efficient and robust bifunctional non-precious metal electrocatalysts, used for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), are crucial to develop water splitting commercial applications. Herein, a bottom-up self-assembly strategy is proposed to construct ternary electrocatalysts of nitrogen-doped graphene-like carbon layers encapsulated MoxC (x = 1, 2) and Ni3Fe alloy nanoparticles (MoxC/Ni3Fe@GL) for efficient water electrolysis. The optimized sample (0.27MoxC/Ni1.5Fe@GL, 0.27 represent the mass of ammonium molybdate in the precursor) requires overpotentials (η10) of 88 and 150, 265 mV in 0.5 M H2SO4 for HER and 1.0 M KOH for HER and OER, respectively. Furthermore, as a bifunctional electrocatalyst in a two-electrode cell, 0.27MoxC/Ni1.5Fe@GL requires only 1.523 V at 10 mA cm−2, which surpasses the noble metal RuO2(+)||Pt/C(−) in 1.0 M KOH electrolyte, and shows excellent stability by working at 20 mA cm−2 long as 150 h. The superior electrocatalytic performance can mainly originate from MoxC and Ni3Fe alloys synergistically effected results. The partial doping of Ni or Fe atoms into Mo2C optimizes the electronic structure, making the intrinsic activity enhanced. On the other hand, the incorporation of MoxC heterophases effectively inhibits the Ni3Fe nanoparticles agglomeration, benefitting to expose more active sites. Moreover, the protection of encapsulated thin N-doped graphene-like carbon layers for the nanoparticles against corrosion, guarantees the long-time durability. This work provides a potential general bottom-up self-assembly approach to construct high-performance electrocatalysts with multiphase heterostructures with enriched abundant active sites and enhanced intrinsic activity for energy coversion fields.