A low-content CeOx dually promoted Ni3Fe@CNT electrocatalyst for overall water splitting

Abstract

Rational construction of low-cost and high-performance electrocatalysts for water splitting is crucial for the advancement of renewable hydrogen fuel. Hybridizing heterojunctions or noble metals is one typical strategy used to boost the electrocatalytic performance for either the oxygen evolution reaction (OER) or hydrogen evolution reaction (HER). Here, low-content CeO_x (3.74 wt%) is introduced into Ni₃Fe nanoparticle-encapsulated carbon nanotubes (Ni₃Fe@CNTs/CeO_x), with both the OER and HER activities boosted, as a bifunctional electrocatalyst for overall water splitting. The composite is derived by pyrolyzing a mixture of melamine/ternary NiFeCe-layered double hydroxide. The composite electrocatalyst requires low overpotentials of 195 and 125 mV at 10 mA cm⁻² in 1.0 M KOH, respectively, which are superior to those of Ni₃Fe@CNTs/NF (313 and 139 mV) and CeO_x/NF (345 and 129 mV), and in particular, OER overpotentials of 320 and 370 mV at 50 and 100 mA cm⁻², respectively. Moreover, the composite-assembled electrolyzer for overall water splitting requires a current density of 10 mA cm⁻² at a decent cell voltage of 1.641 V. Furthermore, the enhancement is elucidated by the synergistic effect: the dual role of CeO_x in boosting the OER and HER, the highly conductive carbonaceous CNTs, large electrochemically active surface area and low charge-transfer resistance. The results can offer an effective route for designing and preparing low-cost and high-efficiency electrocatalysts for electrocatalytic water splitting.