A MoS2-Co9S8-NC heterostructure as an efficient bifunctional electrocatalyst towards hydrogen and oxygen evolution reaction

Interface engineering of hollow Janus-structured NiCoP/P-MoS2 heterojunction as self-supported electrode enables boosted alkaline hydrogen evolution reaction

Transition metal phosphorus (TMPs) and sulfides have attracted extensive attention as important candidates to replace noble metal-based hydrogen evolution (HER) catalysts. However, the insufficient specific surface area, low conductivity and easy detachments from electrode seriously affect the HER catalytic activity and stability. Herein, a novel self-supported hollow Janus-structured NiCoP/P-MoS2 heterojunction is designed on carbon cloth (CC) as high-performance electrocatalyst for alkaline HER. The binder-free NiCoP/P-MoS2/CC electrode with well-dispersed hollow structure exhibits acceptable durability and low overpotential, which requires overpotential of 52.6 mV to reach 10 mA cm-2, far superior to that of NiCoP/CC (111.2 mV), P-MoS2/CC (213.3 mV) electrode and also the corresponding NiCoP/P-MoS2 powder catalyst (113.1 mV). Experimental and theoretical results confirm that heterointerface interaction can improve the electronic state, accelerate charge transfer and optimize hydrogen adsorption energy, resulting in boosted HER kinetic process. Additionally, self-supported strategy is conducive to tightly anchoring high-quality active substances with well-organized hollow array structure, which significantly prevents the catalyst agglomeration and shedding, leading to the improved HER stability. This work offers valuable insights into the catalytic mechanisms and provides an avenue for designing hierarchical architecture for highly efficient and stable HER electrocatalysts.

Enhancing the electrochemical activity of zinc cobalt sulfide via heterojunction with MoS2 metal phase for overall water splitting

The integration of diverse components into a single heterostructure represents an innovative approach that boosts the quantity and variety of active centers, thereby enhancing the catalytic activity for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) in the water splitting process. In this study, a novel, hierarchically porous one-dimensional nanowire array comprising zinc cobalt sulfide and molybdenum disulfide (MoS2@Zn0.76Co0.24S) was successfully synthesized on a Ni foam substrate using an efficient and straightforward hydrothermal synthesis strategy. The incorporation of the metallic phase of molybdenum disulfide elevates the electronic conductivity of MoS2@Zn0.76Co0.24S, resulting in impressively low overpotentials. At 20, 50, and 100 mA cm-2, the overpotentials for oxygen evolution reaction (OER) are merely 90 mV, 170 mV, and 240 mV, respectively. Similarly, for hydrogen evolution reaction (HER), the overpotentials are 169 mV, 237 mV, and 301 mV at the same current densities in 1.0 M potassium hydroxide solution. The utilization of the MoS2@Zn0.76Co0.24S /NF electrolyzer demonstrates its exceptional performance as a catalyst in alkaline electrolyzers. Operating at a mere 1.45 V and 10 mA cm-2, it showcases outstanding efficiency. Achieving a current density of 405 mA cm-2, the system generates hydrogen at a rate of 3.1 mL/min with a purity of 99.997%, achieving an impressive cell efficiency of 68.28% and a voltage of 1.85 V. Furthermore, the MoS2@Zn0.76Co0.24S /NF hybrid exhibits seamless integration with solar cells, establishing a photovoltaic electrochemical system for comprehensive water splitting. This wireless assembly harnesses the excellent performance of the hybrid nanowire, offering a promising solution for efficient, durable, and cost-effective bifunctional electrocatalysts in the realm of renewable energy.

Engineering Double Sulfur-Vacancy in CoS1.097@MoS2 Core-Shell Heterojunctions for Hydrogen Evolution in a Wide pH Range

Heterostructured nanomaterials have arisen as electrocatalysts with great potential for hydrogen evolution reaction (HER), considering their superiority in integrating different active components but are plagued by their insufficient active site density in a wide pH range. In this report, double sulfur-vacancy-decorated CoS1.097@MoS2 core-shell heterojunctions are designed, which contain a primary structure of hollow CoS1.097 nanocubes and a secondary structure of ultrathin MoS2 nanosheets. Taking advantage of the core-shell type heterointerfaces and double sulfur-vacancy, the CoS1.097@MoS2 catalyst exhibits pH-universal HER performance, achieving the overpotentials at 10 mA cm-2 of 190, 139, and 220 mV in 0.5 M H2SO4, 1.0 M KOH, and 1.0 M PBS, respectively. Systematic theoretical results show that the double sulfur-vacancy can endow the CoS1.097@MoS2 core-shell heterojunctions with promoted electron/mass transfer and enhanced reactive kinetics, thus boosting HER performance. This work clearly demonstrates an indispensable role of double sulfur-vacancy in enhancing the electrocatalytic HER performance of core-shell type heterojunctions under a wide pH operating condition.

Microflower-like Co9S8@MoS2 heterostructure as an efficient bifunctional catalyst for overall water splitting

The development of a distinguished and high-performance catalyst for H₂ and O₂ generation is a rational strategy for producing hydrogen fuel via electrochemical water splitting. Herein, a flower-like Co₉S₈@MoS₂ heterostructure with effective bifunctional activity was achieved using a one-pot approach via the hydrothermal treatment of metal-coordinated species followed by pyrolysis under an N₂ atmosphere. The heterostructures exhibited a 3D interconnected network with a large electrochemical active surface area and a junctional complex with hydrogen evolution reaction (HER) catalytic activity of MoS₂ and oxygen evolution reaction (OER) catalytic activity of Co₉S₈, exhibiting low overpotentials of 295 and 103 mV for OER and HER at 10 mA cm⁻² current density, respectively. Additionally, the catalyst-assembled electrolyser provided favourable catalytic activity and strong durability for overall water splitting in 1 M KOH electrolyte. The results of the study highlight the importance of structural engineering for the design and preparation of cost-effective and efficient bifunctional electrocatalysts.

A flower-like Co₉S₈@MoS₂ heterostructure was prepared as efficient bifunctional electrocatalyst for overall water splitting by a sample one-pot approach.

Electronic modulation of cobalt-molybdenum oxide via Te doping embedded in carbon matrix for superior overall water splitting

Developing heteroatom incorporation into the lattice of host materials as bifunctional electrocatalysts is an effective strategy to promote electrochemical water splitting but challenges remain for catalytic activity modulation. Herein, Te-doped...

Nitrogen-Doped Mixed-Phase Cobalt Nanocatalyst Derived from a Trinuclear Mixed-Valence Cobalt(III)/Cobalt(II) Complex for High-Performance Oxygen Evolution Reaction

Because of a continuous increase in energy demands and environmental concerns, a focus has been on the design and construction of a highly efficient, low-cost, environmentally friendly, and noble-metal free electrocatalyst for energy technology. Herein we report facile synthesis of the mixed-valence trinuclear cobalt complex 1 by the reaction of 2-amino-1-phenylethanol and CoCl₂·6H₂O in methanol as the solvent at room temperature. Further, 1 was reduced by using aqueous N₂H₄ as a simple reducing agent, followed by calcination at 300 °C for 3 h, yielding a nitrogen-doped mixed phase cobalt [β-Co(OH)₂ and CoO] nanocatalyst (N@MPCoNC). Both 1 and N@MPCoNC were characterized by various physicochemical techniques. Moreover, 1 was authenticated by single-crystal X-ray diffraction studies. The hybrid N@MPCoNC reveals a unique electronic and morphological structure, offering a low overpotential of 390 mV for a stable current density of 10 mA cm^-2 with high durability. This N@MPCoNC showed excellent electrocatalytic as well as photocatalytic activity for oxygen evolution reaction compared to 1.

A Co-MOF-derived Co9S8@NS-C electrocatalyst for efficient hydrogen evolution reaction

The exploitation of efficient hydrogen evolution reaction (HER) electrocatalysts has become increasingly urgent and imperative; however, it is also challenging for high-performance sustainable clean energy applications. Herein, novel Co9S8 nanoparticles embedded in a porous N,S-dual doped carbon composite (abbr. Co9S8@NS-C-900) were fabricated by the pyrolysis of a single crystal Co-MOF assisted with thiourea. Due to the synergistic benefit of combining Co9S8 nanoparticles with N,S-dual doped carbon, the composite showed efficient HER electrocatalytic activities and long-term durability in an alkaline solution. It shows a small overpotential of -86.4 mV at a current density of 10.0 mA cm-2, a small Tafel slope of 81.1 mV dec-1, and a large exchange current density (J 0) of 0.40 mA cm-2, which are comparable to those of Pt/C. More importantly, due to the protection of Co9S8 nanoparticles by the N,S-dual doped carbon shell, the Co9S8@NS-C-900 catalyst displays excellent long-term durability. There is almost no decay in HER activities after 1000 potential cycles or it retains 99.5% of the initial current after 48 h.

Activating the hydrogen evolution activity of Pt electrode via synergistic interaction with NiS2

Electrocatalytic hydrogen evolution reaction (HER) is a green approach to produce high-quality hydrogen fuel. Developing efficient electrocatalyst is the key to realize cost-effective HER. Pt is the state-of-the-art HER catalyst so far. However, the use of Pt for HER is limited by its high cost. Thus, it is essential to lower down the usage of Pt in the electrocatalyst by improving the intrinsic activity of Pt. In this work, we propose to achieve this goal by introducing synergistic interaction between Pt and substrate material (NiS₂). The favorable synergy interaction can modify the d band structure of Pt (111) facet and modulate the hydrogen adsorption on Pt (111), which enhances the intrinsic electrocatalytic activity of Pt. The effectiveness of this strategy is demonstrated with both experimental and theoretical investigations.

Highly efficient electrocatalysts for overall water splitting: mesoporous CoS/MoS2 with hetero-interfaces

Mesoporous CoS/MoS2 with abundant heterogeneous interfaces was faciley synthesized from a bimetallic hybrid zeolitic imidazolate framework, which showed excellent catalytic activity and reaction kinetics in both the HER and OER in 1 M KOH. Meanwhile, as a cathode and anode in water splitting electrocatalysis, it delivers a low cell voltage of 1.61 V at 10 mA cm-2 and excellent durability.

Flower-like nanosheets directly grown on Co foil as efficient bifunctional catalysts for overall water splitting

Hydrogen generation through electrochemical water decomposition is a promising method to address the global energy crisis. Herein, we report the synthesis of a series of flower-like Mo₃S₄/Co_1-xS composites on Co foil (Mo₃S₄/Co_1-xS@CF) as high-performance electrochemical water-splitting catalysts in an alkaline environment. The flower-like array structure of Mo₃S₄/Co_1-xS@CF not only increases the electrochemically active surface area of ​​the catalyst, but also facilitates the release of bubbles generated, resulting in enhanced catalytic activity. For the hydrogen evolution reaction, the Mo₃S₄/Co_1-xS@CF electrode exhibits good stability and excellent catalytic activity in 1.0 M KOH (η₁₀ = 105 mV), 1.0 M PBS (η₁₀ = 92 mV) and 0.5 M H₂SO₄ (η₁₀ = 68 mV) solutions. For the oxygen evolution reaction, the electrode displays excellent stability and catalytic activity in 1.0 M KOH solution (η₁₀ = 215 mV). When used for overall water splitting in 1.0 M KOH solution, Mo₃S₄/Co_1-xS@CF achieves a current density of 10 mA cm^-2 at a low potential of 1.58 V and maintains it stably for 40 h. This study presents a simple method for preparing transition metal-based bimetallic composite catalysts for efficient hydrogen production.