Accelerating the Electrocatalytic Performance of NiFe–LDH via Sn Doping toward the Water Oxidation Reaction under Alkaline Condition

Abstract

To generate green hydrogen by water electrolysis, it is vital to develop highly efficient electrocatalysts for the oxygen evolution reaction (OER). The utilization of various 3d transition metal-based layered double hydroxides (LDHs), especially NiFe− LDH, has gained vast attention for OER under alkaline conditions. However, the lack of a proper electronic structure of the NiFe− LDH and low stability under high-pH conditions limit its largescale application. To overcome these difficulties, in this study, we constructed an Sn-doped NiFe−LDH material using a simple wetchemical method. The doping of Sn will synergistically increase the active surface sites of NiFe−LDH. The highly active NiFe−LDH Sn 0 . 015(M) shows excellent OER activity by requiring an overpotential of 250 mV to drive 10 mA/cm 2 current density, whereas the bare NiFe−LDH required an overpotential of 295 mV at the same current density. Also, NiFe−LDH Sn 0 . 015(M) shows excellent long-term stability for 50 h in 1 M KOH and also exhibits a higher TOF value of 0.495 s −1 , which is almost five times higher than that of bare NiFe−LDH. This study highlights Sn doping as an effective strategy for the development of low-cost, effective, stable, self-supported electrocatalysts with a high current density for improved OER and other catalytic applications in the near future.

3D-Printed Hierarchically Micro–Nano-structured NiFe Catalysts for the Stable and Efficient Oxygen Evolution Reaction

“…The process of the OER catalyzed by NiFe 2 O 4 involved the transformation of Fe­(III) to Fe­(IV) promoted by oxygen vacancies (Figure S8). ,, …”

“…The enhanced OER performance of 3D NiFe-HT(urea + NH S8). 19,52,53 Stability is critical to evaluate the catalytic activity of electrodes, and a stability test was conducted for 100 h runs in continuous and intermittent (1 h interval) modes at a constant current of 100 mA cm −2 (Figure 5). The potential is constant during the test period of 100 h (Figure 5a), and the LSV curves after the test do not shift significantly (Figure 5b).…”

“…Self-supported catalysts are of significant interest due to good electrical conductivity, , and commercial Ni foam (NF) is commonly used as the substrate on the surface of which NiFeOH materials are introduced by hydrothermal treatment or electrodeposition using Ni and Fe salts. ,− Such NiFeOH@NF electrocatalysts were reported to exhibit good OER catalytic activity with a low overpotential of 230–300 mV at 10 mA cm –2 , partially due to the numerous interfaces between metals and metal oxides. − NiFe foam was also reported as the substrate to support NiFe-based electrocatalysts by roasting and anodization. , Nevertheless, their stability and catalytic activity were not satisfactory, and it was likely due to the fact that the distribution of active components on the surface of the foam skeleton is not highly uniform and the introduction of other cation impurities from the external sources of Ni and Fe salts may have an adverse effect on the growth and crystallinity of NiFeOH. In this context, we considered that the in situ generation of NiFeOH nanomaterials on a porous NiFe bimetal substrate without the use of external sources of Ni and Fe would avoid such problems.…”

Morphology Modulation and Phase Transformation of Manganese–Cobalt Carbonate Hydroxide Caused by Fluoride Doping and Its Effect on Boosting the Overall Water Electrolysis

“…The problem of global warming and depletion of petroleum resources has increased the demand to investigate and develop clean, renewable, and sustainable energy conversion and regenerative energy sources . Among various candidate devices, water electrolysis is an effective approach and a green route with high efficiency and low cost for energy storage and conversion, which can split water into clean hydrogen fuel from aqueous solutions with zero carbon content and often deemed as a promising energy carrier without emitting any greenhouse gases. − The electrochemical water splitting process includes two half-reactions that generates hydrogen on the cathode and oxygen on the anode with water as its feedstock and can be considered as an abundant and renewable hydrogen source. − However, the practical applications of the water splitting process suffer from some inherent limitations, including the sluggish kinetics of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The anodic oxygen evolution reaction and the cathodic hydrogen evolution reaction are strongly uphill with large overpotentials that hinder the practical applications of water splitting. , The sluggish kinetics of OER and HER in the water splitting process is due to the multistep proton transfer and electron transfer to release both H 2 and O 2 by breaking the O–H bond and forming O–O and/or H–H together.…”

Tailoring Metal–Oxygen Bonds Boosts Oxygen Reaction Kinetics for High-Performance Zinc–Air Batteries

“…The construction of amorphous/crystal heterostructures greatly affects the metal− oxygen bond structure (demonstrated by Raman spectra and XPS and XAS results), weakening the Co−O bond strength with abundant Co defects, and increases the valence state of Co (more Co 3+ ), which optimizes the electronic structure and coordination environment of the catalyst. Moreover, the existence of Sn−O bond will activate nearby Co sites and help to balance their electrons, and the strengthening of Sn−O bond strength can appropriately reduce the oxygen defect concentration to obtain the optimal oxygen defect 52,53. Therefore, we speculate that the optimization of metal− oxygen bond structure (including the tailoring of bond strength and the introduction of Fe−O bond) induced by amorphous/crystalline heterostructure improves the intrinsic catalytic performance, while the increase of specific surface area further increases the number of active sites and synergistically promotes the catalytic performance.…”