Photocatalytic hydrogen production in a noble-metal-free system catalyzed by in situ grown molybdenum sulfide catalyst

Light-driven directional decomposition of ammonia nitrogen coupled with proton migration for efficient hydrogen production

The targeted construction of coupled systems, utilizing the unique features of combined photocatalytic redox reactions, is an effective strategy for enhancing catalytic performance. However, the hydrogen source in photocatalytic ammonia-nitrogen oxidation-coupled systems and the multi-electron proton migration pathways in such synergistic systems remain rarely studied. In this study, MoS2/UiOS-MCS composites were synthesized for the photocatalytic conversion of ammonia-nitrogen wastewater into hydrogen. The edge hydrogen evolution effect of MoS2 and the type-II heterojunction formed between both UiO-66-(SH)2 and MnCdS effectively facilitated the separation and transfer of photogenerated charge carriers. The composites exhibited a synergistic hydrogen production rate of 787.42 μmol g-1 h-1, 22 times higher than that of pure MCS, and the nitrogen selectivity is 99.05 %. In situ EPR and controlled experiments identified •NH2 as the intermediate product; Isotope tracing experiments revealed that the protons in hydrogen primarily originate from water, while protons from ammonia nitrogen are transported from the oxidation site to the reduction site. The mechanisms of ammonia nitrogen oxidation, proton transport pathways between reaction sites, and their contributions to hydrogen evolution were elucidated, and new insights were provided for designing photocatalytic synergistic systems and optimizing photocatalyst performance.

In situ self-exsolved ultrasmall Fe2P quantum dots from attapulgite nanofibers as superior cocatalysts for solar hydrogen evolution

Developing highly active, stable, and cost-efficient cocatalysts for photocatalytic H₂ evolution is pivotal in the area of renewable energy conversion. Herein, we present a straightforward, low-temperature phosphidation strategy for in situ exsolving doped Fe ions from natural attapulgite (ATP) nanofibers into a supported Fe₂P cocatalyst for the photocatalytic H₂ evolution reaction (HER). The resulting Fe₂P QDs/ATP features highly dispersed Fe₂P QDs with an average size of <2 nm and a strong interfacial interaction between self-exsolved Fe₂P QDs and the ATP substrate, thus providing ample and stable active sites for the photocatalytic HER. When employed as a cocatalyst, Fe₂P QDs/ATP exhibits superior catalytic activity and notable stability in a molecular system with low-cost xanthene dyes as the photosensitizer under visible light irradiation. More importantly, Fe₂P QDs/ATP can also efficiently and stably catalyze the photocatalytic HER when simply combined with various semiconductor photocatalysts (g-C₃N₄, TiO₂, and CdS). This strategy of exsolving transition metal ions from substrates is an effective yet simple approach for the development of highly active supported HER cocatalysts for renewable and clean energy conversion.

Ni2P nanowire arrays grown on Ni foam as an efficient monolithic cocatalyst for visible light dye-sensitized H2 evolution

Nanostructured H2 evolution cocatalysts are able to promote charge separation and thus enhance the efficiency of the photocatalytic H2 evolution reaction (HER). However, the nanosized cocatalyst particles are easily detached...

Nanostructured Molybdenum Oxides from Aluminium-Based Intermetallic Compound: Synthesis and Application in Hydrogen Evolution Reaction

Characterized by a large surface area to volume ratio, nanostructured metal oxides possess unique chemical and physical properties with applications in electronics, catalysis, sensors, etc. In this study, Mo₃Al₈, an intermetallic compound, has been used as a precursor to obtain nanostructured molybdenum oxides. It was prepared into ribbons by arc-melting and melt-spinning techniques. Single and double-step free corrosion of the as-quenched material have been studied in 1 M KOH, 1 M HF and 1.25 M FeCl₃ at room temperature. In both cases, nanostructured molybdenum oxides were obtained on a surface layer a few microns thick. Two of the as-prepared samples were tested for their electrocatalytic capability for hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ giving low onset potential (−50 mV, −45 mV), small Tafel slopes (92 mV dec⁻¹, 9 mV dec⁻¹) and high exchange current densities (0.08 mA cm⁻², 0.35 mA cm⁻² respectively). The proposed nanostructured molybdenum oxides are cost-effective and sustainable due to the cheap and abundant starting material used and the simple synthetic route, paving the way for their possible application as HER electrocatalysts.

Visible-light-driven H2 production from heterostructured Zn0.5Cd0.5S–TiO2 photocatalysts modified with reduced graphene oxides

Benefiting from the heterojunction structure and compositional features, the optimized 0.5%RGO/50%Zn0.5Cd0.5S–TiO2 composites exhibited considerable photocatalytic activities for H2 evolution.

Recent Advancements and Future Prospects in Ultrathin 2D Semiconductor-Based Photocatalysts for Water Splitting

Ultrathin two-dimensional (2D) semiconductor-mediated photocatalysts have shown their compelling potential and have arguably received tremendous attention in photocatalysis because of their superior thickness-dependent physical, chemical, mechanical and optical properties. Although numerous comprehensions about 2D semiconductor photocatalysts have been amassed up to now, low cost efficiency, degradation, kinetics of charge transfer along with recycling are still the big challenges to realize a wide application of 2D semiconductor-based photocatalysis. At present, most photocatalysts still need rare or expensive noble metals to improve the photocatalytic activity, which inhibits their commercial-scale application extremely. Thus, developing less costly, earth-abundant semiconductor-based photocatalysts with efficient conversion of sunlight energy remains the primary challenge. In this review, it begins with a brief description of the general mechanism of overall photocatalytic water splitting. Then a concise overview of different types of 2D semiconductor-mediated photocatalysts is given to figure out the advantages and disadvantages for mentioned semiconductor-based photocatalysis, including the structural property and stability, synthesize method, electrochemical property and optical properties for H2/O2 production half reaction along with overall water splitting. Finally, we conclude this review with a perspective, marked on some remaining challenges and new directions of 2D semiconductor-mediated photocatalysts.

Confining Mo-activated CoSx active sites within MCM-41 for highly efficient dye-sensitized photocatalytic H2 evolution

Although transition-metal-based sulfides have been identified as efficient catalysts to replace expensive noble metal catalysts for photocatalytic H₂ evolution reaction (HER), their activities are still unsatisfied and could be further improved by controlling their microstructures and electronic structures. Herein, we present an effective strategy to confine highly active Mo-activated CoS_x (Mo-CoS_x) active sites within MCM-41 frameworks by sulfurization of Co-doped MCM-41 during the in situ photoreduction of [MoS₄]^2- in Erythrosin B-triethanolamine (ErB-TEOA) system. It is found that Co-MCM-41 offers not only abundant coordinatively unsaturated Co sites to be activated by Mo and S but also large surface area to effectively disperse the in situ generated amorphous Mo-CoS_x active sites. Under 520 nm irradiation, the most efficient Mo-CoS_x/MCM-41-100 (Si/Co = 100) catalyst exhibits ~7, 3, and 4 times higher H₂ evolution activity than free MoS_x, free Mo-CoS_x, and CoS_x/MCM-41-100, respectively, and an apparent quantum yield (AQY) of 12.3% for H₂ evolution. Furthermore, when Mo-CoS_x/MCM-41-100 was sensitized with a more stable fluorescein (FL) dye, the photocatalytic system shows a sustainable H₂ evolution activity in a 20 h reaction, showing the good stability of Mo-CoS_x/MCM-41-100 catalyst. This work provides a new insight into the design and development of highly active hybrid H₂ evolution catalysts based on transition metals for highly efficient and large-scale solar energy conversion to clean H₂ energy.

Novel dealloying-fabricated NiCo2S4 nanoparticles with excellent cycling performance for supercapacitors

In this work, NiCo₂S₄ nanoparticles for supercapacitors are successfully synthesized with a top-down strategy, using a novel dealloying method with an ion exchange reaction. The surface morphology and x-ray diffraction investigations demonstrated that NiCo₂S₄ nanoparticles are interconnected by ligaments of the synthesized sample. The dealloyed NiCo₂S₄ shows an enhanced electrochemical performance of about 1132.5 F g^-1 at 0.5 A g^-1; kinetic analysis implies a surface-controlled contribution from NiCo₂S₄ (53.86% capacitive contributions). Notably, the NiCo₂S₄//AC (active carbon) device displays a comparatively high energy density (22.83 Wh kg^-1), maximum power density (1327.1 W kg^-1) and superior cycling performance (capacitance retention of 108% after 30 000 cycles).

In situ growth and activation of an amorphous MoSx catalyst on Co-containing metal–organic framework nanosheets for highly efficient dye-sensitized H2 evolution

In situ grown amorphous MoS_x on Co-containing MOF nanosheets could efficiently catalyze visible light H₂ evolution in an ErB-sensitized system.

Insight into the factors influencing the photocatalytic H2 evolution performance of molybdenum sulfide

The specific surface area and composition are found to be the key factors influencing the photocatalytic performance of MoS_2+x.

Ultrasound-assisted Synthesis of Ag-ZnS/rGO and its Utilization in Photocatalytic Degradation of Tetracycline Under Visible Light Irradiation

Recent improvements based on heterojunction nanocomposites have opened new possibilities in photocatalysis. In this research, an ultrasound-assisted coprecipitation method was used to fabricate silver, zinc sulfide and reduced graphene oxide (Ag-ZnS/rGO) nanocomposite, and characterization results indicated that 3% Ag-ZnS spherical nanoparticles are successfully embedded in rGO matrix. The potential of the Ag-ZnS/rGO, as a visible light active photocatalyst, was assessed through optimizing degradation of Tetracycline (TC) by response surface methodology. It was found that the photocatalytic degradation of TC increased with an increase in the amount of nanocomposite and irradiation time, whereas it decreased with increasing the initial TC concentration. Under the optimal conditions (10 mg L^-1 of TC, 1.25 g L^-1 of Ag-ZnS/rGO, at pH = 7, and irradiation duration 110 min), more than 90% of the TC was degraded. The study of the mechanism of the photocatalytic process disclosed that the synergistic role of surface plasmon resonance (SPR) induced by Ag nanoparticles and p-type semiconductor feature of rGO leads to ZnS semiconductor stimulation in the visible light region. Eventually, a pseudo-first order kinetics model was developed based on the proposed mechanism. The obtained results highlight the role of Ag-ZnS/rGO nanophotocatalyst toward degradation of some antibiotics under visible light.

CoAl-layered double hydroxide nanosheets as an active matrix to anchor an amorphous MoSx catalyst for efficient visible light hydrogen evolution

CoAl LDH nanosheet supported MoS_x efficiently catalyzes H₂ evolution from an erythrosin B–triethanolamine molecular system under visible light (≥420 nm).

High-performance Förster resonance energy transfer-based dye-sensitized photocatalytic H2 evolution with graphene quantum dots as the homogeneous energy donor

A highly efficient dye sensitized photocatalytic H₂ evolution system based on Förster resonant energy transfer has been developed by employing N,S codoped graphene quantum dots as energy donor.

Highly active dye-sensitized photocatalytic H2 evolution catalyzed by a single-atom Pt cocatalyst anchored onto g-C3N4 nanosheets under long-wavelength visible light irradiation

A single-atom Pt cocatalyst anchored onto g-C₃N₄ nanosheets could efficiently catalyze H₂ evolution from an Eosin Y-sensitized system under 520 nm irradiation.

Thiomolybdate [Mo3S13]2−nanocluster: a molecular mimic of MoS2active sites for highly efficient photocatalytic hydrogen evolution

As a MoS₂edge site mimic, the [Mo₃S₁₃]²⁻nanocluster can efficiently catalyze H₂evolution from a Ru(bpy)₃²⁺–H₂A molecular system under visible light.

In-Situ Fixation of All-Inorganic Mo-Fe-S Clusters for the Highly Selective Removal of Lead(II)

The selective adsorption by suitable substrate materials is considered one of the most economical methods. In this work, an all-inorganic bimetallic Mo-Fe-S cluster is facilely achieved through in situ chemical fixation of tetrathiomolybdate (TTM) on Fe₃O₄ nanoparticles (NPs) at room temperature (donated as FeMoS NPs). The bimetallic building blocks on the obtained FeMoS NPs possess a monovacancy species of sulfur, endowing FeMoS NPs with a selectivity order of Zn²⁺, Mn²⁺, Ni²⁺ < Cd²⁺ ≪ Cu²⁺ < Pb²⁺ for metal-ion adsorption, a novel application for the Mo-Fe-S clusters. Particularly, with the highest selectivity for Pb²⁺ (K_d ≈ 10⁷), which is about 3 × 10³-1 × 10⁶ times higher than those for other ions and has exceeded that of a series of outstanding sorbents reported for Pb²⁺, FeMoS NPs can efficiently reduce the concentration of Pb²⁺ from ∼10 ppm to an extremely low level of ∼1 ppb. This facile and rational fabrication of the Mo-Fe-S cluster with Fe₃O₄ represents a feasible approach to cheaply develop novel and efficient materials for the selective removal of lead(II).

Recent advances in 2D materials for photocatalysis

Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.

Efficient photocatalytic hydrogen production over eosin Y-sensitized MoS2

An uncapped and agglomerated MoS₂ catalyst was solvothermally synthesized and exhibited excellent hydrogen production activity under sensitization of eosin Y.

Water-soluble MoS3 nanoparticles for photocatalytic H2 evolution

Polyvinylpyrrolidone (PVP)-modified MoS3 nanoparticles with unusual water solubility up to 1.0 mg mL(-1) were synthesized through a facile hydrothermal method in the presence of thioacetic acid. The amorphous nanoparticles wrapped by PVP have sizes of around 2.5 nm, which represent the smallest MoS3 clusters reported. The photocatalytic performance of the MoS3 nanoparticles was evaluated under visible light for H2 evolution using xanthene dyes as photosensitizers. The quantum efficiency of the optimized system for H2 evolution under green light irradiation (520 nm) is up to 36.2 %, which is comparable with those of other excellent photocatalytic systems involving earth-abundant catalysts. The excellent photocatalytic activity can be attributed to its good dispersion in water, amorphous nature and limited layers with abundant surface active sites, and possibly higher conduction band potential for proton reduction and larger indirect band gap for a longer lifetime of the excited electrons.

Polypyrrole-Ru(2,2'-bipyridine)3(2+)/MoSx structured composite film as a photocathode for the hydrogen evolution reaction

The development of photoelectrochemical devices for solar light-driven water splitting and H2 production requires new strategies for the fabrication of materials that combine the necessary photoredox and catalytic properties, to allow the hydrogen evolution reaction (HER) to take place at a low overvoltage under visible light irradiation. We report the first example of a structured composite, synthesized by electrodeposition of MoSx cocatalyst into a photosensitive Ru complex film deposited onto carbon electrodes by electropolymerization of a pyrrole-functionalized Ru(II)(2,2'-bipyridine)3(2+). Composite films show efficient photocatalytic activity for HER. Our study highlights the great simplicity of this versatile electrochemical procedure to synthesize photocathodes.

Low loaded palladium nanoparticles on ethylenediamine-functionalized cellulose as an efficient catalyst for electrochemical hydrogen production

In this study, for the first time, a carbon paste electrode was modified with palladium nanoparticles supported on ethylenediamine-functionalized cellulose, and its performance for electrocatalytic hydrogen production was examined.