Preparation of 3D nanostructured MnCo₂S₄ as a robust electrocatalyst for overall water splitting

Abstract

The exploitation and use of efficient and inexpensive electrochemical catalysts accelerate overall water splitting, which rapidly produces oxygen and hydrogen. In this work, MnCo2S4 is grown on nickel foam by a two‐step method, hydrothermal and sulfuration method. Experiments have shown that the resulting MnCo2S4/NF exhibits a low overpotential of 310 mV to achieve a current density of 50 mA cm−2 in 1.0 M potassium hydroxide for oxygen evolution reaction (OER). In addition, the MnCo2S4/NF exhibits a low overpotential of only 167 mV at 10 mA cm−2 for hydrogen evolution reaction (HER). Furthermore, MnCo2S4/NF is acted as a bifunctional water splitting catalyst, and in 1.0 M potassium hydroxide, in order to maintain a current of 10 mA cm−2, a low battery voltage of 1.61 V is required. The nanostructure, which provides a large specific surface area, which in turn increases the reactive sites, facilitates contact of large areas of water with the catalyst, and rapid transfer of electrons. At the same time, through a series of characterization (XRD, SEM and XPS), it is proved that the catalyst is efficient and stable under alkaline condition.

Metal–Organic Framework-Derived Cu-Doped Co9S8 Nanorod Array with Less Low-Valence Co Sites as Highly Efficient Bifunctional Electrodes for Overall Water Splitting

“…The catalytic activity of Cu-Co 9 S 8 -6h is greatly improved, only need 260 mV overpotential to drive 50 mA cm –2 , which is 60, 130, 140, 180, and 200 mV lower than those of Co 9 S 8 -6h (320 mV), Cu-Co 9 S 8 -8h (390 mV), Cu-Co 9 S 8 -4h (400 mV), Cu-Co-MOF/NF (440 mV), and Cu-Co­(CO 3 ) (OH)/NF (460 mV), respectively (Figure d). Compared with the previously reported noble-free metal electrode, the Cu-Co 9 S 8 -6h catalyst showed excellent electrochemical activity than that of the reported materials, for example, Cu 3 P/CF (∼412 mV), carbonate-Co­(OH) 2 /NF (∼337 mV), MnCo 2 S 4 NA/TM (∼325 mV), NiFe-LDH@NiFe-Bi/CC (∼294 mV), Al-CoP/NF (∼280 mV), and RuO 2 (330 mV) (Figure S10). The dynamics of catalytic materials are reflected by the Tafel slope (Figure b), the Cu-Co 9 S 8 -6h has a lower Tafel slope (76.7 mV/dec) than those of Cu-Co 9 S 8 -8h (79.3 mV/dec), Cu-Co 9 S 8 -4h (106.4 mV/dec), Cu-Co-MOF/NF (141.9 mV/dec), and Cu-Co­(CO 3 )­(OH)/NF (284.7 mV/dec) (Figure b).…”

Controlled Synthesis of Cr‐Co0.85Se Nanoarrays for Water Splitting at an Ultralow Cell Voltage of 1.43 V

“…The set voltage is −1.06 V–1 V, the scan is increased from 10 mV/s to 50 mV/s in increments of 10 mV each time for HER. The standard hydrogen electrode voltage (NHE) in all test environments is converted to a reversible hydrogen electrode potential (RHE) by the following equation, E[V versus normal hydrogen electrode (NHE)]=E(V versus Ag/AgCl)+0.197 (1) and E(V versus RHE)=E(V versus NHE)+0.059 × pH (2), (1) and (2) are combined to give: E(V versus RHE)=E(V versus Ag/AgCl)+0.197+0.059 × pH and the final measurement data was corrected by IR . The Tafel equation is calculated from the Tafel slope: η = b log j + a , where η is the overpotential, b is the Tafel slope and j is the current density.…”

“…The standard hydrogen electrode voltage (NHE) in all test environments is converted to a reversible hydrogen electrode potential (RHE) by the following equation, E[V versus normal hydrogen electrode (NHE)] = E(V versus Ag/AgCl) + 0.197 (1) and E(V versus RHE) = E(V versus NHE) + 0.059 × pH (2), (1) and (2) are combined to give: E(V versus RHE) = E(V versus Ag/AgCl) + 0.197 + 0.059 × pH and the final measurement data was corrected by IR. [16] The Tafel equation is calculated from the Tafel slope: η = b log j + a, where η is the overpotential, b is the Tafel slope and j is the current density. The overpotential η is calculated as follows: η = E vs. RHEÀ 1.23 V. The electrochemical double layer capacitor (C dl ) is fitted by different rate images obtained in cyclic voltammetry.…”

Ultrathin NiCo-LDH regulated by CuNiCo trimetallic spinel sulfides as highly active and stable electrocatalysts for overall water splitting

“…12,28 Due to excellent electrochemical performances, bimetallic spinel sulfides have drawn much interest and further been extensively utilized in various fields, such as supercapacitors, 29,30 Li-ion batteries, 31 and electrocatalysts. 32,33 A lot of research shows that NiCo 2 S 4 can be used as an excellent bifunctional electrocatalyst for overall water splitting. [34][35][36] The conductivity and stability can be further improved by polymetallic synergy.…”