Dual-Cation-Coordinated CoFe-Layered Double-Hydroxide Nanosheets Using the Pulsed Laser Ablation Technique for Efficient Electrochemical Water Splitting: Mechanistic Screening by In Situ/Operando Raman and Density Functional Theory Calculations

Abstract

Cation modulation engineering is employed to tune the intrinsic activity and electronic structure of electrocatalysts for water electrolysis. Here, we designed two-dimensional cobalt–iron-layered double-hydroxide (CoFe-LDH) ultrathin nanosheets by pulsed laser ablation in an aqueous medium. The CoFe-LDH nanosheets exhibited abundant electrochemically active sites and a large surface area. The optimal Co0.5Fe0.5-LDH exhibited a low overpotential of 270 mV during half-cell oxygen evolution reactions (OERs), whereas Co0.25Fe0.75-LDH delivered 365 mV at 10 mA/cm2 during hydrogen evolution reactions (HERs). The bifunctional electrocatalyst exhibited an outstanding water electrolyzer performance at a cell voltage of ∼1.89 V at 10 mA/cm2 and admirable stability for long-run repetitive cycles. The synergistic effect between the modulated cations resulted in better conductivity, and the mass transfer facilitated the HER and OER. We demonstrated that this facile approach can facilitate the engineering of a highly stable and efficient electrode for renewable electrochemical energy conversion reactions.

Modulating the Electronic Structure of Ni/NiO Nanocomposite with High‐Valence Mo Doping for Energy‐Saving Hydrogen Production via Boosting Urea Oxidation Kinetics

“…The iR (a potential drop owing to solution resistance) compensation of linear sweep voltammetry polarization (LSV) curves depicted in Figure 4a shows that Ni/MNO-10 exhibited an excellent OER performance, which requires only 283 and 374 mV to attain current densities of 10 and 100 mA cm À2 , respectively. These values are considerably lower than that of other as-synthesized samples and similar to the state-of-the-art IrO [34] The Tafel slope and EIS characterizations results imply that the Mo doping can enhance the efficiency of the charge transfer process, which could ultimately lead to an effective OER process. [51] Besides, the mass activity of each electrocatalyst was measured at various potential values (1.50-1.60 vs RHE) to demonstrate the intrinsic activity of catalysts during reactions (Figure 4e).…”

“…As the potential value increased, R ct decreased, indicating the high absorption of the OER intermediate and resulting in an expansion in the OER rate. [ 34 ] The Tafel slope and EIS characterizations results imply that the Mo doping can enhance the efficiency of the charge transfer process, which could ultimately lead to an effective OER process. [ 51 ]…”

“…In particular, we mainly focused on the potential of the PLA technique to create different nanostructured materials with varying morphologies and sizes by regulating the laser condition and reaction solution parameters, which were then used for electrocatalytic applications. [32,[34][35][36] However, few reports are only available for the synthesis of Ni/NiO and NiO nanoparticles via the pulsed laser ablation (PLA) technique. [37,38] According to our knowledge, no reports are available, specifically on the Mo-doped Ni/NiO nanoparticles fabricated using the PLA-assisted technique and their UOR performances.…”

Constructing an n–n junction between CoFe-LDH and NiCoP as bifunctional electrocatalysts for efficient overall water splitting

“…3a) was split into four characteristic peaks corresponding to Fe 2+ (710.4/725.9 eV), Fe 3+ (714.2/ 729.5 eV), and two satellite peaks (720.9/734.4 eV) of the Fe 2p 3/2 and Fe 2p 1/2 core levels, respectively. 38,39 In the highresolution Co 2p spectrum, the peak at 776.2 eV was assigned to Co 2p 3/2 of metal phosphide (Fig. 3b).…”

Role of aluminium hydrides in localised corrosion of aluminium revealed by operando Raman spectroscopy

“…26,27 Two studies have investigated FFC in situ, 31 or quasi in situ, 10 by infrared spectroscopy on aluminium. In situ and operando vibrational spectroscopy gives on the other hand significant advantages for obtaining direct insight into reactions mechanisms and processes, 32,33 such as the study of solvation, 34,35 reaction intermediates in electrocatalysis or corrosion, [36][37][38][39] oxides forming in electrocatalytical processes, [40][41][42] corrosion and oxidation products, [43][44][45][46][47][48] cathodic delamination, 49 or corrosion inhibitors. 50,51 Raman spectroscopy as a vibrational spectroscopic method in a confocal microscope combines the possibility of optical imaging with information related to chemical composition of corrosion products on the mm length scale; it can be applied in the field, 52 and is a popular tool, e.g.…”