Ni Single Atoms and Ni Phosphate Clusters Synergistically Triggered Surface‐Functionalized MoS₂ Nanosheets for High‐performance Freshwater and Seawater Electrolysis

Abstract

Two‐dimensional metal dichalcogenides have been evidenced as potential electrocatalysts for hydrogen evolution reaction (HER); however, their application is limited by a poor oxygen evolution reaction (OER) activity due to insufficient number/types of multi‐integrated active sites. In this study, we report a novel bifunctional catalyst developed by simultaneous engineering of single nickel atoms (NiSA) and nickel phosphate clusters (NiPi) to synergistically trigger surface‐functionalized MoS2 nanosheets (NSs) resulting in high reactivities for both HER and OER. The NiSA‐NiPi/MoS2 NSs material exhibits a fairly Pt‐like HER behavior with an overpotential of 94.0 mV and a small OER overpotential of 314.0 mV to reach 10 mA cm−2 in freshwater containing 1.0 M KOH. Experimental results of the catalyst are well supported by theoretical study, which reveals the significant modulation of electronic structure and enrichment of electroactive site number/types with their reasonably adjusted free adsorption energy. For evaluating practicability, the NiSA‐NiPi/MoS2 NSs‐based electrolyzer delivers effective operation voltage of 1.62, 1.52, and 1.66 V at 10 mA cm−2 and superior long‐term stability as compared to Pt/C//RuO2 system in freshwater, mimic seawater, and natural seawater, respectively. The present study indicates that the catalyst is a promising candidate for the practical production of green hydrogen via water electrolysis.

Nanorod Array-Based Hierarchical NiO Microspheres as a Bifunctional Electrocatalyst for a Selective and Corrosion-Resistance Seawater Photo/Electrolysis System

“…As shown in Figure a, the comparison of LSV responses between the NRAHM-NiO (−, +) electrolyzer with Pt/C (−) ||Pt/C (+) and Pt/C (−) ||IrO 2(+) pairs confirm that the NRAHM-NiO-based electrolyzer shows excellent overall water-splitting performance in mimic seawater medium, requiring small cell voltages of 1.66 and 2.01 V to drive current densities of 100 and 500 mA cm –2 , respectively. Such catalytic activity is not only superior compared to the benchmark Pt/C (−) ||IrO 2(+) (1.78 and 2.31 V, respectively) and Pt/C (−) ||Pt/C (+) (1.89 and 2.73 V, respectively) paired systems but also superior to those of previously reported catalysts for the overall electrochemical water splitting in mimic seawater displayed in Figure b. ,,,,− In addition, such efficiency even outperforms that of most efficient precious metal-free bifunctional electrocatalysts for overall alkaline freshwater splitting (complete details are provided in Table S6, Supporting Information). Since catalysts usually work at high temperatures in industrial conditions (60–80 °C), measuring overall water electrolysis stability at high temperatures is of significant importance for realizing industrial applications.…”

“…The Tafel slope can be used to analyze the rate-determining step (RDS) of the OER using the Butler–Volmer equation . The Tafel slope values of NRAHM-NiO indicate a rapid OER catalytic kinetic process resulting in an improvement in the rate of the OER, which could involve a combination of three different mechanistic pathways, including the adsorbate evolution mechanism (AEM) with the Eley–Rideal type, the lattice oxygen mechanism at the oxygen site (LOM-O), and the lattice oxygen mechanism at the metal site (LOM-M). ,− Therefore, the dominant type of active site determines which step is the RDS since multiple types of active sites can coexist on the same catalyst. Electrochemical impedance spectroscopy (EIS) analysis is performed to study the charge-transfer resistance between each catalyst and the electrolyte (Figure d).…”

“…HER/OER electrocatalysts based on Ni have drawn immense attention as promising earth-abundant water-splitting electrocatalysts. , An effective bifunctional electrocatalyst requires the modification of Ni-based electrodes, which can be accomplished through different strategies, including morphology engineering and active atom doping. − Another main issue in water-splitting approaches is the scarcity of freshwater. In fact, freshwater is the main source of electrolytes for water electrolysis, and there will be a heavy strain on freshwater resources if we run large-scale hydrogen generation .…”

Highly efficient and durable P, Ru–CeO2 self-supporting electrodes toward industrial-level hydrogen production

“…To date, there have been significant advances in developing efficient electrolytic saline-alkali water catalysts, including metal nitrides, 25,26 phosphides, 27,28 sulfides, 29,30 and so on. To reach the level of industrial water splitting, the electrode material must meet the following requirements: (1) low cost; (2) exceptional catalytic activity (>1000 mA cm −2 ); (3) excellent long-term stability (>100 h and >300 mA cm −2 ) and corrosion resistance to Cl − (>3.5%).…”

Bimetallic Atom Dual-Doped MoS2-Based Heterostructures as a High-Efficiency Catalyst To Boost Solar-Assisted Alkaline Seawater Electrolysis

“…Usually, SA catalysts are favorably stabilized by coordination to heteroatom (N, P, and S)-doped nanocarbons, which are low cost, robust, and tunable. , However, the powder form of products requires a polymer binder to make an electrode, thus significantly reducing catalytic activities and stability. Some emerging supports, , especially two-dimensional (2D) MoS 2 nanosheet (NS)-based hybrids, − have recently been reported as respective alternatives to stabilize SA catalysts, along with the successful construction of effective binder-free electrodes. Furthermore, the introduction of SAs into the inert in-plane domain of 2D MoS 2 can stimulate the formation of coordinatively unsaturated S atoms, thus favorably triggering its edge and in-plane area activities .…”