Regulating Complex Transition Metal Oxyhydroxides Using Ni₃S₂: 3D NiCoFe(oxy)hydroxide/Ni₃S₂/Ni Foam for an Efficient Alkaline Oxygen Evolution Reaction

Abstract

In electrochemical decomposition of water, the slow kinetics of the anodic oxygen evolution reaction (OER) is a challenge for efficient hydrogen production. Heterointerface engineering is a desirable way to rationally design electrocatalysts for the OER. Herein, we designed and fabricated a nanoparticle flower-like NiCoFe(oxy)hydroxide catalyst in situ grown on the surface of Ni 3 S 2 /NF to construct a heterojunction via combining hydrothermal and electrodeposition methods. The heterostructure exhibits a smaller overpotential of 254 mV at a large current density of 100 mA cm −2 in 1 M KOH than that of pristine NiCoFeO x H y /NF (356 mV) and Ni 3 S 2 /NF (471 mV). Tafel and electrochemical impedance spectroscopy further showed a favorable kinetics during electrolysis. The role of the substrate Ni 3 S 2 was explored via density functional theory calculations. Our calculations found that SO x on the Ni 3 S 2 surface is a strong nucleophilic group and the synergy effect between Fe and SO x could break *OOH to reduce the Gibbs energy. We also found that the contribution of SO x in sulfates to the OER activity could be negligible. Furthermore, a series of comparative samples were prepared to test this synergy effect. Our experiments indicated that the introduction of Ni 3 S 2 is beneficial. The present contribution provides an important helpful insight into the design and fabrication of novel and highly efficient heterostructure electrocatalysts by introducing nucleophilic groups at the interface.

Synergistic Coupling of Charge Extraction and Sinking in Cu5FeS4/Ni3S2@NF for Photoassisted Electrocatalytic Oxygen Evolution

“…The other two peaks at 44.5 and 51.8° come from the metallic Ni foam (JCPDS no. 70-1849) . Notably, the diffraction peaks of both Cu 5 FeS 4 and Ni 3 S 2 show a slight shift to the higher angle, which can be attributed to the lattice distortion caused by the intimate combination between Cu 5 FeS 4 and Ni 3 S 2 . , In addition, to further demonstrate the actual composition of Cu 5 FeS 4 /Ni 3 S 2 @NF, the energy-dispersive X-ray (EDX) spectrum was measured.…”

“…The other two peaks at 44.5 and 51.8°come from the metallic Ni foam (JCPDS no. 70-1849) 27. Notably, the diffraction peaks of both Cu 5 FeS 4 and Ni 3 S 2 show a slight shift to the higher angle, which can be attributed to the lattice…”

“…Before test, the samples were covered on a Pt network (1.0 × 1.0 cm 2 ) and employed as working electrodes, and Pt wire was used as the counter electrode, from which the TPV signal was recorded by an oscilloscope after processing by an amplifier. 27 Notably, the diffraction peaks of both Cu 5 FeS 4 and Ni 3 S 2 show a slight shift to the higher angle, which can be attributed to the lattice 28,29 In addition, to further demonstrate the actual composition of Cu 5 FeS 4 /Ni 3 S 2 @NF, the energydispersive X-ray (EDX) spectrum was measured. As shown in Figure S1, the atomic ratios of Cu, Fe, Ni, and S are 8.15, 1.24, 58.41, and 32.20%, respectively, in which the high content of Ni mainly comes from NF.…”