Few-layer MoS2 and Pt nanoparticles Co-anchored on MWCNTs for efficient hydrogen evolution over a wide pH range

Electron rearrangement at the crystalline-amorphous heterogeneous interface boosts alkaline hydrogen production

Modifying the platinum (Pt) local reaction microenvironment is a critical and complex challenge in enhancing electrochemical performance. Herein, amorphous Co(OH)2 and crystalline Pt (labeled as ac-Pt@Co(OH)2) featuring abundant crystalline-amorphous (c-a) interfaces are designed to boost the hydrogen evolution reaction (HER). The engineered structure creates an advantageous chemical environment at the local level, enhancing hydrogen adsorption efficiency and resulting in exceptional HER performance. The ac-Pt@Co(OH)2 achieves a low Tafel slope of 28.5 mV dec-1 and requires merely 95 mV overpotential to reach 200 mA cm-2 in alkaline electrolyte (1 M KOH), surpassing those of conventional Pt/C catalysts (39.4 mV dec-1, 256 mV). In situ advanced characterization investigations reveal dynamic electron rearrangement at the c-a interface, where Co species initially accept electrons from Pt to optimize the adsorption of *H species and then donate electrons to Pt for accelerating reduction kinetics. Theoretical calculations reveal that amorphous Co(OH)2 promotes the dissociation of water molecules to produce active *H, and electron rearrangement at the c-a interface downshifts the d-band center, thereby optimizing the *H adsorption strength and enhancing HER activity. The ac-Pt@Co(OH)2-based alkaline anion-exchange membrane water electrolyzer (AEMWE) maintains a current density of 500 mA cm-2 over 500 h.

An efficient hydrogen evolution catalyst constructed using Pt-modified Ni3S2/MoS2 with optimized kinetics across the full pH range

Electrocatalyst materials play a crucial role in determining the efficiency of the hydrogen evolution reaction (HER), directly influencing the overall effectiveness of energy conversion technologies. Ni3S2/MoS2 heterostructures hold substantial promise as bifunctional catalysts, owing to their synergistic electronic characteristics and plentiful active sites. However, their catalytic efficacy is impeded by the relatively elevated chemisorption energy of hydrogen-containing intermediates, which constrains their functionality in different pH environments. In order to mitigate this limitation, trace amounts of Pt are introduced into the heterostructure, intending to enhance electronic transport and refining chemisorption energies, thereby facilitating significant enhancements in both HER and oxygen evolution reaction (OER) activities over a wide pH range. It is revealed that the Pt-modified catalyst achieves exceptional HER performance, requiring merely 64 mV and 83 mV overpotentials to attain a current density of 100 mA cm-2 in acidic and alkaline media, respectively. Furthermore, theoretical simulations corroborate that Pt modification optimizes local electronic configurations and augments electronic transfer, contributing to its superior catalytic performance. This investigation underscores the pivotal role of Pt modification in propelling the practical application of Ni3S2/MoS2 heterostructures as highly efficient and pH-universal bifunctional catalysts.

Space-Confinement and in Situ Reduction of Pt with 1T-MoS2 for Exceptional Hydrogen Evolution Reaction in Simulated Seawater

Efficient catalysts for hydrogen generation from seawater are essential for advancing clean energy technologies. In this study, we present a straightforward method for producing Pt nanoparticles enclosed within metallic 1T-phase MoS2 nanosheets on graphite paper as a promising catalyst for the hydrogen evolution reaction (HER). The resulting 14.3 wt % Pt-MoS2 nanosheets demonstrate an ultralow onset potential of 65.6 mV vs the reversible hydrogen electrode (RHE) and a minimal Tafel slope of 64 mV/dec with remarkable stability and durability in simulated seawater, offering comparable catalytic performance to the 40 wt % Pt/C commercial catalyst at a lower cost. This exceptional hydrogen production is attributed to the robust reducing ability of 1T-phase MoS2 and the confinement of Pt nanoparticles within the MoS2 interlayers and nanosheets. Our findings highlight the significance of this approach in developing practical and sustainable electrocatalysts for seawater splitting. This research represents a crucial step toward a greener and more sustainable future, leveraging innovative catalyst design strategies for clean energy production.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

Hierarchical SiC-Graphene Composite Aerogel-Supported Ni-Mo-S Nanosheets for Efficient pH-Universal Electrocatalytic Hydrogen Evolution

MoS₂ exhibits good prospects in electrocatalytic hydrogen evolution. Whereas, the electrocatalytic property of MoS₂ is restrained by its insufficient active sites, low electrical conductivity, and slow water dissociation processes. Herein, an aerogel composed of silicon carbide (SiC) and graphene (SiCnw-RGO) was constructed by growing SiC nanowires (SiCnw) in the graphene aerogel (RGO) via the CVD method, and then Ni-Mo-S nanosheets were hydrothermally synthesized on the SiCnw-RGO composite aerogel to develop an efficient pH-universal electrocatalyst. Ni-Mo-S nanosheets supported on SiCnw-RGO (Ni-Mo-S@SiCnw-RGO) exhibit an interesting hierarchical three-dimensional interconnected structure of composite aerogel. The optimal Ni-Mo-S@SiCnw-RGO electrocatalyst exhibits excellent catalytic performance with low Tafel slopes of 60 mV/dec under acidic conditions and 90 mV/dec under alkaline conditions. Density functional theory calculations demonstrate a composite catalyst exhibits advantageous hydrogen adsorption free energy and water dissociation energy barrier. This study provides a reference to design an efficient hierarchical aerogel electrocatalyst.

Engineering Rich Active Sites and Efficient Water Dissociation for Ni-Doped MoS2/CoS2 Hierarchical Structures toward Excellent Alkaline Hydrogen Evolution

Besides improving charge transfer, there are two key factors, such as increasing active sites and promoting water dissociation, to be deeply investigated to realize high-performance MoS₂-based electrocatalysts in alkaline hydrogen evolution reaction (HER). Herein, we have demonstrated the synergistic engineering to realize rich unsaturated sulfur atoms and activated O-H bonds toward the water for Ni-doped MoS₂/CoS₂ hierarchical structures by an approach to Ni doping coupled with in situ sulfurizing for excellent alkaline HER. In this work, the Ni-doped atoms are evolved into Ni(OH)₂ during alkaline HER. Interestingly, the extra unsaturated sulfur atoms will be modulated into MoS₂ nanosheets by breaking Ni-S bonds during the formation of Ni(OH)₂. On the other hand, the higher the mass of the Ni precursor (m_Ni) for the fabrication of our samples, the more Ni(OH)₂ is evolved, indicating a stronger ability for water dissociation of our samples during alkaline HER. Our results further reveal that regulating m_Ni is crucial to the HER activity of the as-synthesized samples. By regulating m_Ni to 0.300 g, a balance between increasing active sites and promoting water dissociation is achieved for the Ni-doped MoS₂/CoS₂ samples to boost alkaline HER. Consequently, the optimal samples present the highest HER activity among all counterparts, accompanied by reliable long-term stability. This work will promise important applications in the field of electrocatalytic hydrogen evolution in alkaline environments.

Electrocatalytic Water Splitting: From Harsh and Mild Conditions to Natural Seawater

Electrocatalytic water splitting is regarded as the most effective pathway to generate green energy-hydrogen-which is considered as one of the most promising clean energy solutions to the world's energy crisis and climate change mitigation. Although electrocatalytic water splitting has been proposed for decades, large-scale industrial hydrogen production is hindered by high electricity cost, capital investment, and electrolysis media. Harsh conditions (strong acid/alkaline) are widely used in electrocatalytic mechanism studies, and excellent catalytic activities and efficiencies have been achieved. However, the practical application of electrocatalytic water splitting in harsh conditions encounters several obstacles, such as corrosion issues, catalyst stability, and membrane technical difficulties. Thus, the research on water splitting in mild conditions (neutral/near neutral), even in natural seawater, has aroused increasing attention. However, the mechanism in mild conditions or natural seawater is not clear. Herein, different conditions in electrocatalytic water splitting are reviewed and the effects and proposed mechanisms in the three conditions are summarized. Then, a comparison of the reaction process and the effects of the ions in different electrolytes are presented. Finally, the challenges and opportunities associated with direct electrocatalytic natural seawater splitting and the perspective are presented to promote the progress of hydrogen production by water splitting.

Facile Synthesis of 1T-Phase MoS2 Nanosheets on N-Doped Carbon Nanotubes towards Highly Efficient Hydrogen Evolution

1T-phase molybdenum disulfide is supposed to be one of the non-precious metal-based electrocatalysts for the hydrogen evolution reaction with the highest potential. Herein, 1T-MoS₂ nanosheets were anchored on N-doped carbon nanotubes by a simple hydrothermal process with the assistance of urea promotion transition of the 1T phase. Based on the 1T-MoS₂ nanosheets anchored on the N-doped carbon nanotubes structures, 1T-MoS₂ nanosheets can be said to have highly exposed active sites from edges and the basal plane, and the dopant N in carbon nanotubes can promote electron transfer between N-doped carbon nanotubes and 1T-MoS₂ nanosheets. With the synergistic effects of this structure, the excellent 1T-MoS₂/ N-doped carbon nanotubes catalyst has a small overpotential of 150 mV at 10 mA cm⁻², a relatively low Tafel slope of 63 mV dec⁻¹, and superior stability. This work proposes a new strategy to design high-performance hydrogen evolution reaction catalysts.