MoS₂ Decoration Followed by P Inclusion over Ni-Co Bimetallic Metal–Organic Framework-Derived Heterostructures for Water Splitting

Abstract

Demonstrating a highly efficient non-noble bifunctional catalyst for complete water electrolysis remains challenging because of kinetic limitations and crucial importance for future energy harvesting. Herein, a low-cost, integrated composite of a Ni–Co metal–organic framework decorated with thin MoS2 nanosheets was synthesized by a simple hydrothermal method followed by carbonization and phosphorization for electrochemical oxygen and hydrogen evolution reactions. Such a composite heterostructure exhibits outstanding performance in the electrocatalysis process with a lower overpotential of 184 mV for the oxygen evolution reaction (OER) and 84 mV for the hydrogen evolution reaction (HER) in 1.0 M KOH and 0.5 M H2SO4 electrolytes to reach a current density of 10 mA cm–2, with a slight Tafel slope of 63 mV dec–1 for the OER and 96 mV dec–1 for the HER. The obtained results are far better than those of the commercial benchmark catalyst. Furthermore, online gas chromatography quantifies the amount of hydrogen generation in a symmetric cell as equal to 0.002121 moles with an energy efficiency of about 2.237 mg/kWh. Thus, the composite electrode’s remarkable performance is further demonstrated as a potentially viable alternative non-noble electrocatalyst for energy conversion reactions.

Metal‐Thiolate Framework for Electrochemical and Photoelectrochemical Hydrogen Generation

“…This is indicative of the Volmer‐Tafel mechanism of H 2 generation in acidic media. Other Cu‐sulfide‐based materials that have reported faster kinetics have shown considerably high overpotential, such as Cu 2 S micro‐hexagons, which have a Tafel slope of 28 mV dec −1 but η (@10 mA cm −2 ) of 312 mV RHE , or Cu 2 NRs@CoS/CF, which has a Tafel slope of 31 mV dec −1 but η (@10 mA cm −2 ) of 235 mV RHE [31,32] . The surface exchange current density of the electrode system was 1.5×10 −2 mA cm −2 .…”

“…Other Cu-sulfide-based materials that have reported faster kinetics have shown considerably high overpotential, such as Cu 2 S micro-hexagons, which have a Tafel slope of 28 mV dec À 1 but η(@10 mA cm À 2 ) of 312 mV RHE , or Cu 2 NRs@CoS/CF, which has a Tafel slope of 31 mV dec À 1 but η(@10 mA cm À 2 ) of 235 mV RHE . [31,32] The surface exchange current density of the electrode system was 1.5 × 10 À 2 mA cm À 2 . To understand the electrochemical active surface area (ECSA), the double-layer capacitance (C dl ) of MTF-1 was calculated at À 0.03 V RHE (Figure 7c,d).…”

“…It is pertinent to mention that metal sulfides are often used as single standing electrodes or composites for electrochemical/PEC HER. [31][32][33] However, they show substantial corrosion during electrolysis. Further, incorporation of organic linkers in the cluster of metal sulfides can change the redox properties as well as conductivity of the material, [34] which could lead to reduced photocorrosion.…”

“…By tuning the framework composition, the morphology, architecture, surface interaction, and/or adsorption/diffusion of proton can be largely enhanced. It is pertinent to mention that metal sulfides are often used as single standing electrodes or composites for electrochemical/PEC HER [31–33] . However, they show substantial corrosion during electrolysis.…”

Self-supported CoMoO4/NiFe-LDH core–shell nanorods grown on nickel foam for enhanced electrocatalysis of oxygen evolution

“…15 In this situation of progressively depleted resources, a suitable, efficient and pollution-free industrial technology is urgently needed to manufacture hydrogen and oxygen in massive amounts. 16 The most promising technology for producing hydrogen and oxygen is electrolysis of water, 17,18 due to its no pollution, high efficiency, and a simple concept and operation.…”