Metal Cocatalysts Research Articles

Mixed atomic-scale electronic configuration as a strategy to avoid cocatalyst utilization in photocatalysis

To enhance the activity of photocatalysts for hydrogen production and CO2 conversion, noble metal cocatalysts as electron traps and/or acceptors such as platinum or gold are usually utilized. This study hypothesizes that mixing elements with heterogeneous electronic configurations and diverse electronegativities can provide both acceptor and donor sites of electrons to avoid using cocatalysts. This hypothesis was examined in high-entropy oxides (HEOs), which show high flexibility for atomic-scale compositional changes by keeping their single- or dual-phase structure. A new high-entropy oxide was designed and synthesized by mixing elements with an empty d orbital (titanium, zirconium, niobium and tantalum) and a fully occupied d orbital (gallium). The synthesized oxide had two phases (88 wt% orthorhombic (Pbcn) and 12 wt% monoclinic (I2/m)) with an overall composition of TiZrNbTaGaO10.5. It exhibited UV and visible light absorbance with a low bandgap of 2.5 eV, low radiative electron-hole recombination and oxygen vacancy generation due to mixed valences of cations. It successfully acted as a photocatalyst for CO and CH4 production from CO2 conversion and hydrogen production from water splitting without cocatalyst addition. These findings confirm that introducing heterogeneous electronic configurations and electronegativities can be considered as a design criterion to avoid the need to use cocatalysts.

ZnIn2S4 nanosheets with geometric defects for enhanced solar-driven hydrogen evolution and wastewater treatment

The key to development of high-performance and low cost photocatalysts hydrogen evolution and waste degradation is to realize efficient photo-generated charge carrier separation and surface catalytic reaction simultaneously without noble metal co-catalyst. To achieve this goal, a noble metal free ZnIn2S4 photocatalyst with geometric defects has been constructed, in which [In-S]4 tetrahedral vacancies (named as (InS)v) on the surface are created by removing the In and S atoms. Further mechanistic investigation has revealed that the (InS)v not only works as the active sites for reductive reaction, but also improves photo-generated electron-hole separation. As a result, the solar-driven hydrogen evolution rate reaches 10.70 mmol/gh without co-catalyst after optimizing the densities of the (InS)v. The apparent quantum efficiency at 380 nm, 395 nm, 420 nm, 450 nm and 520 nm is as high as 14.0 %, 17.1 %, 12.1 %, 8.2 % and 2.4 %, respectively. In addition, these photocatalysts also achieve a rate of 97.78 % and 91.27 % of RhB and MO within 3 and 60 min, respectively. This work show-case a novel approach to develop dual functional and noble metal free photocatalysts for efficiently utilizing solar energy for hydrogen generation and wastewater treatment.

(Ag–NiO)/g-C3N4 with enhanced photocatalytic activity for hydrogen evolution under simulated sunlight

g-C3N4 is a promising metal-free photocatalyst for hydrogen production, whose application is difficult due to the low mobility of charge carriers and rapid electron-hole recombination. Here we propose a new route to improve its response to simulated sunlight and prevent electron-hole recombination by grafting mixed Ag–NiO (1:1 nominal Ag/NiO weight ratio) materials, as an alternative to platinum group metal co-catalysts. g-C3N4 was prepared by urea pyrolysis, whereas Ag–NiO was prepared by a co-precipitation method, and then the composites were prepared by physical mixing using sonication-grinding. The presence of Ag–NiO on the surface plays a key role in accepting excited electrons and enhancing their lifetime for a subsequent reduction of protons to hydrogen. Hydrogen production was carried out from the photoreforming of ethanol under simulated sunlight. The results revealed that 2% (Ag–NiO)/g-C3N4 is effective among others with 5.2 times higher H2 production than unmodified g-C3N4. The percentage of ethanol in the ethanol/water ratio is very important as we have found that with increasing its quantity, the evolution of hydrogen becomes significant.

Trinuclear iron-oxo cocatalyst regulating new electron transfer pathway in Pt loaded bismuth oxychloride for efficient photocatalytic hydrogen production

BiOCl, a traditional p-type semiconductor, finds extensive application in photocatalytic oxidation and degradation, whereas it is less common in photocatalytic water splitting and hydrogen production. Here, the photocatalytic hydrogen production performance of black BiOCl has been examined by the introduction of noble metal platinum and cocatalyst trinuclear iron-oxo cluster. During the 5-h photocatalytic process, the established system significantly augments the hydrogen production efficiency of black BiOCl by an estimated factor of 8.53. Under illumination, trinuclear iron-oxo clusters provide electron recombination with holes in the valence band of the catalyst, thereby increasing the utilization of photogenerated electrons. Additionally, since the specific energy level structure has a significant impact on the cocatalyst function, trinuclear iron-oxo clusters can be suitable in a variety of photocatalytic systems. This new endeavor might present creative design approaches and low-cost cocatalyst alternatives for the photocatalytic hydrogen evolution from the water splitting of conventional p-type semiconductor materials.

High-Performance Methanol Oxidation via Ni12-Metal8/CNF Catalyst for Fuel Cell Applications

In this work, non-precious electrocatalysts were synthesized using the electrospinning technique. Ni12M8/CNF (M = Cd, Co, and Cu) catalysts were successfully prepared in a fixed ratio to withstand the optimum transition metal co-catalyst in addition to the role of CNFs as support in ion-charge movement through the catalyst surface. The prepared catalysts were physically studied by XRD, SEM, and TEM. The electrochemical activity was verified using different fuel concentrations, different sweeping scan rates, and electrochemical impedance. Ni12Cu8/CNFs showed the highest electrochemical activity reaching 152 mA/cm2 through different methanol concentrations. The outstanding performance is attributed to the large active surface area provided by carbon nanofibrous that eases the charge carrier transfer through the untrapped surface of the catalyst. The electrochemical tests suggest that Ni12Cu8/CNFs have the lowest ohmic impedance resistance ensuring the highest efficiency of the designed catalyst. The obtained results serve as an efficient catalyst for direct methanol electrooxidation reactions and suggest a possible application of a low-cost, easily accessible, and large surface area established via the preparing method.

Enhanced Photocatalytic Paracetamol Degradation by NiCu-Modified TiO2 Nanotubes: Mechanistic Insights and Performance Evaluation.

Anodic TiO2 nanotube arrays decorated with Ni, Cu, and NiCu alloy thin films were investigated for the first time for the photocatalytic degradation of paracetamol in water solution under UV irradiation. Metallic co-catalysts were deposited on TiO2 nanotubes using magnetron sputtering. The influence of the metal layer composition and thickness on the photocatalytic activity was systematically studied. Photocatalytic experiments showed that only Cu-rich co-catalysts provide enhanced paracetamol degradation rates, whereas Ni-modified photocatalysts exhibit no improvement compared with unmodified TiO2. The best-performing material was obtained by sputtering a 20 nm thick film of 1:1 atomic ratio NiCu alloy: this material exhibits a reaction rate more than doubled compared with pristine TiO2, enabling the complete degradation of 10 mg L-1 of paracetamol in 8 h. The superior performance of NiCu-modified systems over pure Cu-based ones is ascribed to a Ni and Cu synergistic effect. Kinetic tests using selective holes and radical scavengers unveiled, unlike prior findings in the literature, that paracetamol undergoes direct oxidation at the photocatalyst surface via valence band holes. Finally, Chemical Oxygen Demand (COD) tests and High-Resolution Mass Spectrometry (HR-MS) analysis were conducted to assess the degree of mineralization and identify intermediates. In contrast with the existing literature, we demonstrated that the mechanistic pathway involves direct oxidation by valence band holes.

Enhanced Photocatalytic Hydrogen Production Activity Driven by TiO2/(MoP/CdS): Insights from Powder Particles to Thin Films.

Transitioning from powder photocatalysts to thin film photocatalysts is one of the necessary steps toward industrializing photocatalytic hydrogen production. Herein, we reported the integration of non-noble metal cocatalyst MoP decorated with TiO2 and CdS, forming TiO2/(MoP/CdS) for ultraviolet-visible light utilization. The designed powder TiO2/(MoP/CdS) composites achieved a superior hydrogen production rate of 42.2 mmol g-1 h-1, which is 30.1 times that of TiO2/CdS, performing the highest activity among the TiO2-CdS-based composite photocatalysts. Moreover, we fabricated a thin film from TiO2/(MoP/CdS) powder, which exhibited comparable photocatalytic activity for hydrogen production, achieving 35.5 mmol g-1 h-1 and maintaining long-term stability for 150 h. The outstanding performance was attributed to the ability of the TiO2/(MoP/CdS) composite photocatalysts to absorb both visible and ultraviolet light. Additionally, the heterojunction formed between TiO2 and CdS also played a significant role in the overall photocatalyst activity. This cost-effective catalyst holds promise for future large-scale industrial applications.

Unraveling the Microstructure‐Property Relationship of Fe Single‐Atoms via Introducing Asymmetric P‐Coordination for Photocatalytic Hydrogen Evolution

AbstractThe local atomic environments of single‐atom photocatalysts play a decisive role in determining the solar‐to‐hydrogen energy conversion efficiency. However, controllably modulating the microstructure of single‐atom sites to enhance catalytic activity and deeply understanding the structure‐property relationship remain great challenges. Herein, electron‐rich P atoms are introduced to accurately regulate the local coordination environment and electronic configuration of Fe single atoms and construct a unique asymmetrical FeN3P2 motif into carbon nitride (FeN3P2‐CN) for significantly improving the photocatalytic H2 evolution activity and stability. Specifically, in the absence of noble metal cocatalyst and photosensitizer, the FeN3P2‐CN achieves a remarkable H2 evolution rate of 2668.5 µmol g−1 h−1 under visible light irradiation (λ > 420 nm), more than 105 times higher than that of unregulated FeN4 sample. Systematic characterizations and theoretical calculations unveil that the FeN3P2 single‐atom sites not only significantly broaden the photoabsorption region and facilitate the charge separation and interfacial transfer, but also efficiently promote adsorption and activation of H2O. This work paves a promising pathway to design novel single‐atom photocatalysts at the atomic level for achieving highly efficient water‐splitting performance.

M/BiOCl-(M=Pt, Pd, and Au) Boosted Selective Photocatalytic CO2 Reduction to C2 Hydrocarbons via *CHO Intermediate Manipulation.

Selective CO2 photoreduction to C2 hydrocarbons is significant but limited by the inadequate adsorption strength of the reaction intermediates and low efficiency of proton transfer. Herein, an ameliorative *CO adsorption and H2O activation strategy is realized via decorating bismuth oxychloride (BiOCl) nanostructures with different metal (Pt, Pd, and Au) species. Experimental and theoretical calculation results reveal that distinct *CO binding energies and *H acquisition abilities of the metal cocatalysts mediate the CO2 reduction activity and hydrocarbon selectivity. The relatively moderate *CO adsorption and *H supply over Pd/BiOCl endows it with the lowest free energy to generate *CHO, leading to its highest activity of hydrocarbon production. Specifically, the Pt cocatalyst can efficiently participate in H2O dissociation to deliver more *H for facilitating the protonation of the *CHO and *CHOH, thereby favoring CH4 production with 76.51% selectivity. A lower *H supply over Pd/BiOCl and Au/BiOCl results in a large energy barrier for *CHO or *CHOH protonation and thus a more thermodynamically favored OC─CHO coupling pathway, which endows them with vastly increased C2 hydrocarbon selectivity of 81.21% and 92.81%, respectively. The understanding of efficient C2 hydrocarbon production in this study sheds light on how materials can be engineered for photocatalytic CO2 reduction.

Direct Operando Identification of Reactive Electron Species Driving Photocatalytic Hydrogen Evolution on Metal-Loaded Oxides.

Performing operando spectroscopy under practical reaction conditions and extracting spectral components correlating with reaction activity are crucial in elucidating the reactive species in photocatalysis. However, the observation of weak signals corresponding to reactive photogenerated species is frequently hampered under reaction conditions owing to intense background signals originating from thermally induced species unrelated to the photoinduced reactions. Herein, by synchronizing the millisecond periodic excitations of photocatalysts with a Michelson interferometer used for FT-IR spectroscopy, we succeeded in significantly suppressing the signals derived from thermally excited electrons and observing the reactive photogenerated electrons contributing to the photocatalytic hydrogen evolution. This demonstration was achieved for metal-loaded oxide photocatalysts under steam methane reforming and water splitting conditions. Although it has long been conventionally believed that loaded metal cocatalysts function as sinks for reactive photogenerated electrons and active sites for reduction reactions, we found that the free electrons in the metal cocatalysts were not directly involved in the reduction reaction. Alternatively, the electrons shallowly trapped in the in-gap states of oxides contributed to enhancing the hydrogen evolution rate upon the loading of metal cocatalysts. We verified that the electron abundance in the in-gap states was clearly correlated to the reaction activity, suggesting that metal-induced semiconductor surface states formed in the periphery of the metal cocatalyst play key roles in the photocatalytic hydrogen evolution. Our microscopic insights shift a paradigm on the traditionally believed role of metal cocatalysts in photocatalysis and provide a fundamental basis for rational design of the metal/oxide interfaces as promising platforms for nonthermal hydrogen evolution.

Joule heating assisted solvothermal growth of C3N4 on carbon paper for effective photothermal-photocatalytic water splitting for hydrogen evolution

Photocatalysis combined with photothermal effect has become a promising process for highly-efficiently production of H2. In this work, C3N4 was solvothermally grown on carbon paper and further construction of vacancies by fast Joule heating treatment. The substrate carbon paper could increase the photothermal evaporation of water, and the fabricated vacancies could accelerate the charge separation. Furthermore, the temperature increased because of the photothermal synergistic effect, which was favorable for the H2 evolution reaction. Based on the above, the CP/SCN-NVs system achieved efficient H2 evolution in deionized water without sacrificial agent and precious metal co-catalysts, with a hydrogen evolution rate of 2248.83 μmol m-2 h−1, which was 41.3 times higher than the C3N4 suspension system. Overall, this work offered a new approach for efficient H2 evolution in photothermal-photocatalytic dual-phase systems.

Enhanced hydrogen production performance via noble-metal-free amorphous NiZnSx-CS co-catalyst with novel gradient coating structure

In photocatalytic water splitting for hydrogen production, co-catalyst is a key factor in enhancing the efficiency of photocatalyst. Various inexpensive co-catalysts besides noble metal co-catalysts have been developed; however, the illumination of the relationship between the structure and performance remains a challenge. Here, we present a bimetallic sulfide co-catalyst denoted as NiZnSx-CS with amorphous and gradient coating structures to achieve highly efficient hydrogen production activity. Upon coupling the co-catalyst with CdS, the hydrogen production rate of CdS loaded with NiZnSx-CS reaches 38.0 mmol/g/h, 11.0, 40.0 and 161.0 times higher than that loaded with bulk NiZnSx, 1.0 %Pt and naked CdS, respectively. The co-catalyst with an amorphous and gradient coating structure shows large capacitance and thus facilitates efficient storage, transfer, and separation of photo-excited electrons of semiconductors, effectively reducing the over-potential of hydrogen production. The co-catalyst also has a large specific surface area and excellent hydrophilicity attributed to the abundant active sites and intimate contact with the reactant. Additionally, the coordination structure and chemical environment of NiZnSx-CS elucidated using X-ray absorption spectroscopy (XAS). The intermediates and the role of lactic acid and water on the surface of NiZnSx-CS after irradiation are determined by in situ Fourier transform infrared spectroscopy (in situ FT-IR). This work proposes a strategy to develop a highly efficient special structure co-catalyst with suitable capacitance, specific surface area and hydrophilicity.

Ferroelectric polarization-electric field promoted S-scheme CdSe/BaxSr1-xTiO3 for highly efficient solar hydrogen evolution

Coupling the ferroelectric polarization and internal electric field to realize effective separation and migration of photogenerated charges is highly attractive for accomplishing efficient photocatalytic hydrogen production. In this work, an internal electric field modulated S-scheme heterostructure was fabricated by depositing CdSe on ferroelectric BaxSr1-xTiO3 (BxST) through an in-situ growth method. Because of the oriented powerful electron transport driven by the strong spontaneous polarization and internal electric field, the as-synthesized CdSe/BxST heterojunctions demonstrated excellent solar to H2 performance. Without the addition of noble metal cocatalyst, 7% CdSe/B0.8ST exhibited a H2 evolution rate of 1971.8 µmol g-1 h−1 with an apparent quantum yield of 12.1% at 365 nm. Moreover, the obtained heterojunction catalysts exhibit good stability after 12 h continuous irradiation. This work provides a viable strategy on the utilization of ferroelectric polarization and internal electric field strategy to promote charge transfer and separation of S-scheme photocatalysts.

Stable loading of MOF-derived carbon skeleton encapsulated Ni and BiOBr on carbonized cellulose fibers for fabricating high-performance and recyclable photocatalytic paper

The highly dispersed small-size metal co-catalysts can effectively improve the photocatalytic efficiency of semiconductor photocatalysts by separating photogenerated electrons and enriching active sites. However, this system tends to aggregate in the absence of carrier, resulting in the decrease of active sites. Here, MOF-derived carbon skeleton (MDCS) encapsulated Ni nanoparticles (Ni@MDCS) and BiOBr was loaded onto carbonized cellulose fibers (CCF) with the help of polydopamine (PDA) to construct high-performance and recyclable photocatalytic paper for photocatalytic degradation of organic dyes in water. The characterization results showed that MDCS promoted good dispersion of Ni nanoparticles and provided sufficient active sites. And Ni@MDCS as a co-catalyst accelerated the separation of photogenerated carriers in BiOBr. The PDA improved the loading state of Ni@MDCS on CCF and converted into N-doped C in the carbonization process for further increasing the transfer efficiency of photogenerated electrons. In the composite paper, the stable loading of Ni@MDCS/BiOBr hybrid on CCF improved the dispersion and reusability of photocatalyst. The degradation rate of rhodamine B on CCF/PDA-C/Ni@MDCS/BiOBr paper was as high as 94.6 % after 60 min visible light irradiation, which was about 2.5 times higher than that of CCF/BiOBr paper. During 10 cycles, CCF/PDA-C/Ni@MDCS/BiOBr paper maintained high photocatalytic efficiency and good structural stability. This study provides a new way for developing high-performance and recyclable photocatalytic paper.

Induced-aggregates in photocatalysis: An unexplored approach to reduce the noble metal co-catalyst content

Photocatalysis has emerged as a promising and environmentally sustainable solution to produce high-purity hydrogen through ethanol photoreforming. It is commonly accepted that adding co-catalysts, especially noble metals, significantly enhances the catalytic activity of semiconductors. However, the high cost of noble metals such as Pt may limit the real application of this emerging technology. Here we evaluate the possibility of reducing the noble metal loading by creating the appropriate interface between pre-formed semiconductor nanoparticles. Commercial titania (P25) was selected as the semiconductor due to its commercial availability, facilitating the straightforward validation and corroboration of our results. Pt was selected as co-catalyst because one of the most efficient photocatalysts for the ethanol photo-reforming is still based on the use of P25 in combination with Pt. We report that the creation of induced aggregates dramatically improves the total hydrogen produced when very low loadings (≤0.05 wt%) of Pt are used. We have developed a pioneering reactor designed for conducting photoluminescence studies under authentic operational conditions of nanoparticle suspensions in the liquid phase. This approach allows us to obtain the average photoluminescence emission from the P25 agglomerates what it would be impossible to obtain by using standard solid samples holders. Thanks to this equipment, we can conclude that this remarkable improvement of the activity is mainly due to creation of an interface that favors the charge transfer between the particles of the aggregates. According to this, the titania nanoparticles of the agglomerates act as an antenna to collect the photons of the sun-light and produce the photo-excited electrons that will be transferred to the platinum nanoparticles located in the same agglomeration. In contrast, raw P25 with low loadings of Pt would have a high number of titania nanoparticles without platinum, and therefore, inactive. This result would be especially relevant in the case of immobilized photocatalytic systems for real future photocatalytic reactors because the immobilization of the semiconductors would generate similar interactions to the one created by our method. Consequently, the initial semiconductor immobilization followed by the subsequent photo-deposition of the co-catalyst emerges as a promising approach for a substantial reduction of the co-catalyst content.

Photocatalytic Activity of Metal- and Non-Metal-Anchored ZnO and TiO2 Nanocatalysts for Advanced Photocatalysis: Comparative Study

This review article provides useful information on TiO2 and ZnO photocatalysts and their derivatives in removing organic contaminants such as dyes, hydrocarbons, pesticides, etc. Also, the reaction mechanisms of TiO2 and ZnO photocatalysts and their derivatives were investigated. In addition, the impact of adding metallic (e.g., Ag, Co, Pt, Pd, Cu, Au, and Ni) and non-metallic (e.g., C, N, O, and S) cocatalysts to their structure on the photodegradation efficiency of organic compounds was thoroughly studied. Moreover, the advantages and disadvantages of various synthesis procedures of ZnO and TiO2 nanocatalysts were discussed and compared. Furthermore, the impact of photocatalyst dosage, photocatalyst structure, contaminant concentration, pH, light intensity and wavelength, temperature, and reaction time on the photodegradation efficiency were studied. According to previous studies, adding metallic and non-metallic cocatalysts to the TiO2 and ZnO structure led to a remarkable enhancement in their stability and reusability. In addition, metallic and non-metallic cocatalysts attached to TiO2 and ZnO demonstrated remarkable photocatalytic efficiency in removing organic contaminants.

Unraveling active sites regulation and temperature-dependent thermodynamic mechanism in photothermocatalytic CO2 conversion with H2O

In the photothermal synergistic catalytic conversion of CO2 and H2O, the catalyst harnesses solar energy to accumulate heat, thereby elevating the reaction system’s temperature. The influence of this temperature effect on surface chemical reactions remains an underexplored area. Here the impact of temperature on the surface-level thermodynamic reactions and conversion of CO2 with H2O on oxide semiconductors at the atomic scale was investigated using first-principle calculations. 13 different metal oxides and 5 transition metal clusters were used to introduce surface functional sites on the TiO2 supporting catalyst. The potential metal oxide cocatalysts that could be most beneficial to the following conversion of CO2 by H2O were initially screened by calculating the degrees of promotion of CO2 adsorption and activation of surface H to provide protons. The proton donation and hydrogen evolution difficulty from H2O were further analyzed, identifying transition metal cocatalysts that promote direct CO2 hydrogenation. Upon introducing bifunctional sites to facilitate adsorption and reduction, the production of CH3OH and CH4 could be further enhanced through the facilitation of the proton donation process of H2O. The results of Gibbs free-energy calculations revealed that increasing temperature enhances the reaction thermodynamics for each C1 product formation at different surface sites to varying degrees. These findings offer valuable theoretical insights for designing and regulating active sites on oxide semiconductor surfaces for efficient photothermal catalytic CO2 reduction by H2O.

Steering Photooxidation of Methane to Formic Acid over A Priori Screened Supported Catalysts.

Efficient methane photooxidation to formic acid (HCOOH) has emerged as a sustainable approach to simultaneously generate value-added chemicals and harness renewable energy. However, the persistent challenge lies in achieving a high yield and selectivity for HCOOH formation, primarily due to the complexities associated with modulating intermediate conversion and desorption after methane activation. In this study, we employ first-principles calculations as a comprehensive guiding tool and discover that by precisely controlling the O2 activation process on noble metal cocatalysts and the adsorption strength of carbon-containing intermediates on metal oxide supports, one can finely tune the selectivity of methane photooxidation products. Specifically, a bifunctional catalyst comprising Pd nanoparticles and monoclinic WO3 (Pd/WO3) would possess optimal O2 activation kinetics and an intermediate oxidation/desorption barrier, thereby promoting HCOOH formation. As evidenced by experiments, the Pd/WO3 catalyst achieves an exceptional HCOOH yield of 4.67 mmol gcat-1 h-1 with a high selectivity of 62% under full-spectrum light irradiation at room temperature using molecular O2. Notably, these results significantly outperform the state-of-the-art photocatalytic systems operated under identical condition.

A novel noble-metal-free FeS2/Mn0.5Cd0.5S heterojunction for enhancing photocatalytic H2 production activity: Carrier separation, light absorption, active sites

BackgroundThe development of efficient and noble-metal-free photocatalysts is greatly essential for photocatalytic hydrogen production. However, the photocatalytic activity of a single photocatalyst is usually limited for various reasons. MethodsHerein, FeS2/Mn0.5Cd0.5S (FSMCS) heterojunctions were constructed by a simple solvent evaporation method. The morphological characterizations revealed a raspberry-like hollow microsphere structure for FeS2 and irregular granularity for Mn0.5Cd0.5S. Photoluminescence (PL) and electrochemical experiments indicated that the FSMCS composite effectively facilitated the separation of photogenerated electron-hole pairs. The UV–vis diffuse reflectance spectrum (DRS) showed that, in FSMCS composite, the visible light absorption range was effectively expanded to the full visible light. Significant findingsExcellent photocatalytic activity in FSMCS heterojunctions without loading noble metals because FeS2 could serve an active site for hydrogen production. The optimum FSMCS composite had excellent photocatalytic hydrogen production activity (6.1 mmol·g−1·h−1), which was 5.6 and 2.3 times higher than that of the pristine Mn0.5Cd0.5S (1.1 mmol·g−1·h−1) and Mn0.5Cd0.5S-1 %Pt (2.7 mmol·g−1·h−1). Meanwhile, in four round-robin tests, the activity of the 5FSMCS photocatalyst did not significantly decrease. This work proved that combining Mn0.5Cd0.5S and non-precious metal cocatalysts to construct heterojunctions is a promising strategy for photocatalytic hydrogen production.

Fast carrier separation induced by the metal-like O-doped MoS2/CoS cocatalyst for achieving photocatalytic and photothermal hydrogen production

Full solar-spectrum-driven hydrogen (H2) production from water-splitting is highly desirable but remains a great challenge. A heterojunction composite photocatalyst with a full-spectrum absorption range of up to 1020 nm was constructed by introducing 2D/2D metallic oxygen-doped MoS2/CoS (O-MC) nanosheets onto 1D Zn0.1Cd0.9S nanorods (ZCS NR) for photocatalytic and photothermal H2 production. Consequently, the optimal ZMC1.5 heterojunction exhibited a significantly improved H2 production activity of 95.5 mmol g−1 h−1 under 420 nm monowavelength irradiation, which is 13.84 times higher than that of pristine ZCS NR. Even under 1020 nm monowavelength irradiation, the catalyst also shows an expressive H2 generation rate of 0.202 mmol g−1 h−1. Moreover, it gives an apparent quantum yield (AQY) of 39.5% at 420 nm. Femtosecond transient absorption spectroscopy (Fs-TAS) results reveal the multiple intraband and interband excited-charge transitions in the partially occupied band of O-MC and interfacial electron transfer between O-MC and ZCS NR result in the enhancement H2 evolution rate. This study highlights the extended light absorption and special partially occupied energy bands of metallic cocatalysts, which hold great potential for the design and synthesis of efficient full solar-spectrum (UV–vis-NIR light) responsive photocatalysts.