Enhanced H2 Generation Research Articles

Pt nanoclusters as co-catalysts for efficient photocatalytic hydrogen evolution

Photocatalytic water splitting for hydrogen production is an ideal strategy to relieve the energy crisis. In this work, Pt nanoclusters are employed as a co-catalyst to modify g-C3N4 for optimizing the photocatalytic hydrogen evolution performance. Compared with the pristine g-C3N4, the Pt nanoclusterss/g-C3N4 nanocomposites exhibit dramatic enhancement toward H2 production, where the H2 evolution rate of CN-Pt-C2 is nearly 425.1 times higher than pristine g-C3N4. The phase structure, morphology, optical properties, and surface chemical states of the fabricated samples are fully investigated. Based on the systematical characterizations, the reason for the enhanced H2 generation performance is disclosed. It is expected this work can provide a valuable reference for the fabrication of a co-catalyst-based photocatalytic system.

MWCNT/Al–Bi–NaCl nanocomposites for enhanced H2 generation

H2 generation through hydrolysis of Al-composites has received eclectic attention for on-demand H2 applications such as low-power proton exchange membrane fuel cells. In this line, we prepared Multi-Walled Carbon Nanotubes (MWCNT)/Al–Bi–NaCl nanocomposites and tested them for enhanced H2 generation. These nanocomposites are prepared using high-energy ball milling followed by uni-axial cold compaction. H2 generation by these nanocomposites was tested using tap water at room temperature. An excellent maximum H2 generation rate of 13.33 mLg−1s−1 with an H2 yield of 98% and an induction time of less than 10 s is achieved. Analysis of different observations shows that adding an optimum percentage of MWCNT to the Al–Bi–NaCl composite results in flaky morphology, which facilitates easily accessible water pathways, enhancing the H2 generation rate of the nanocomposites. Also, an enhanced number of MWCNT/Al–Bi microgalvanic cells, optimum utilization of electrical conductivity of MWCNT, and dissolution of NaCl favored the H2 generation.

Singlet oxygen species induced by colloidal crystalline carbon nitride induced for efficient H2O2 synthesis with in situ antibacterial effect

Solar-driven hydrogen (H2) and hydrogen peroxide (H2O2) generation over visible-light responsive carbon nitride (CN) photocatalysts for in situ efficient sterilization is a promising and eco-friendly strategy. Herein, a colloidal potassium-ion (K+) intercalated crystalline CN nanosheets (KCCN) photocatalyst was constructed for boosting synergetic H2O2 synthesis with isopropanol (IPA) oxidation and in situ antibacterial effect. The surface hydroxyl (−OH) and cyano (−CN) groups induced by molten salt (KCl)-assisted thermal treatments contributed to the colloidal nature of CN, facilitating for high wettability of KCCN in aqueous solution to gain active hydrogen (H+) from water sustainably. Meaningfully, the enhanced high-energy singlet oxygen species (1O2) produced by KCNN-2 were verified by electron paramagnetic resonance (EPR) and 9,10-anthracenediyl-bis(methylene)-dimalonic acid (ABDA)-fluorescent probe, significantly contributing to H2O2 production and antibacterial effect. Consequently, the optimal KCCN-2 exhibited a much enhanced H2 generation of 4.11 mmol g−1 h−1, and H2O2 production activity of 1.82 mmol L−1 h−1 with acetone yield rate of 47.3 mmol g−1 h−1 under visible-light (λ > 420 nm) irradiation in 10 vol% IPA solution. The in-situ generated H2O2 can be activated to produce reactive oxygen species (ROS), especially 1O2, to effectively kill the Escherichia coli, reaching an improved an antibacterial rate of 89.7% under stimulated sunlight irradiation in 1 h. This work could offer a new insight into the photoinduced ROS for aqueous H2O2 photosynthesis and antibacterial application.

Enhanced H2 Generation via Piezoelectric Reforming of Waste Sugars and Fruits Using Au-Decorated g-C3N4

The food industry is responsible for generating considerable amounts of waste, such as excess fruits and leftover sugars, which contribute to resource depletion and pose environmental challenges. This research delves into the application of gold-modified graphitic carbon nitride nanosheets (Au/CN) as a potent catalyst for the transformation of these food wastes into H2 via piezoelectric reforming during sonication. Au/CN demonstrated a superior rate of H2 evolution compared to pristine g-C3N4 (i.e., 1533.3 vs. 364.9 µmol/g/h) and it maintained its efficiency through multiple cycles of use. The catalytic activity was found to be optimal at a neutral pH level and with increased sugar concentrations. The enhanced catalytic performance of Au/CN was ascribed to the efficient segregation of charge carriers as well as the reduced charge transfer distance. This study underscores the viability of using Au/CN as a means for converting food wastes into a sustainable source of H2 energy.

Enhanced generation of hydrogen through hydrolysis of biochar-coupled magnesium: Analysis of the performance of biochar-support and the effect of metallic coating on biochar

Hydrolysis is regarded as a safe, efficient and adorable approach to generate hydrogen (H2) from magnesium (Mg) or Mg-based materials. In this work, biochar (BC) and ferric oxide (Fe2O3) coated biochar (magnetic biochar: MBC) were synthesized and applied along with Mg as catalysts for an enhanced H2 generation. The Mg-Xwt%Y (X = 1.0, 3.0, 5.0, 10.0, 15.0 and Y = BC, MBC) composites were prepared via ball milling and employed to investigate their hydrolysis performance through kinetics in seawater. Among employed dosages, 10.0 wt% contents exhibited the best hydrolysis performance. Mg-10.0 wt%BC and Mg-10.0 wt%MBC composites after 1 h ball milling generated 820.03 and 828.02 mL/g (conversion yields of 89.03% and 89.99%) H2 in 40 and 10 min, respectively. Further, 10.0 wt% of BC and MBC decreased the hydrolysis kinetic energy of Mg from 63.9 to 41.07 and 17.16 kJ/mol, respectively. MBC has better catalytic effects for Mg hydrolysis compared with those by BC could be due to relatively more functional groups, providing more channels for water molecules to interact with Mg resulting in subsequent enhanced hydrolysis. Hence, MBC increased the reactivity and galvanic corrosion of Mg as well as prevented the formation of passive layer of magnesium hydroxide (Mg(OH)2) on fresh surface of Mg. The performance of MBC-supported Mg in hydrolysis process is anticipated to be essential for the creation of environmentally-friendly portable H2 generators, the use of clean generation of H2 energy and the reduction of environmentally adverse emissions.

Heterojunction of TiO2 nanotubes arrays/Bi2Se3 quantum dots as an effective and stable photoanode for photoelectrochemical H2 generation

The use of semiconductor materials to split water through photoelectrochemical (PEC) processes is a remarkable technique that can transform solar energy into chemical energy, such as H2, in one step. For enhanced H2 generation, efficient separation of electron–hole (e−/h+) pairs and high photogenerated electron conductivity are required for photoanode substrates. In this study, an effective type II heterojunction between Bi2Se3 quantum dots (QDs) and TiO2 nanotube arrays (TNTAs) was constructed by depositing Bi2Se3 QDs on the TNTAs surface. The performance for PEC H2 generation was also investigated. The TNTAs/Bi2Se3 QDs demonstrated the highest photocurrent density of 1.75 mA cm−2, which is 3.8 times greater than bare TNTAs (0.46 mA cm−2) at 1.23 V vs. RHE. They also achieved a high hydrogen generation quantity of 355.8 μmol after 5 h, which is 3.3 times greater than bare TNTAs (105.3 μmol) at 1.23 V vs. RHE. TNTAs and TNTAs/Bi2Se3 QDs photoanodes both exhibited excellent stability for over 7 h. Compared with bare TNTAs, the TNTAs/Bi2Se3 QDs photoanode demonstrated a higher incident photon-to-current conversion efficiency (IPCE) in the UV region and expanded the light response to the visible region due to its lower charge recombination and larger visible light absorption. The exceptional performance of the TNTAs/Bi2Se3 QDs photoanode is due to its proper bandgap energy, which improves the visible light absorption, and its effective charge carrier transfer, which alleviates the recombination of e−/h+ pairs. The modification of TNTAs with Bi2Se3 QDs as a promising metal chalcogenide for improving visible light absorption and PEC water splitting performance has not yet been studied. Therefore, this work paves the way for a facile approach to construct a stable and high-performance photoanode for PEC H2 generation.

Pt clusters in carbon network to enhance photocatalytic CO2 and benzene conversion of WOx/g-C3N4 nanosheets

Noble metals in carbon networks dramatically improve the carrier separation and transfer efficiencies of layered graphic carbon nitride (g-C3N4) based heterostructures for efficient CO2 and benzene photocatalytic conversion. Here, Pt clusters are homogeneously incorporated into ultrathin g-C3N4 nanosheets via multi-step treatment method using the combinations of mechano-chemical pre-reaction and two-step thermal condensation processes. Small Pt nanoparticles with diameters of less than 5 nm are observed and WOx nanobelts with increased oxygen vacancies (as the active sites) are horizontally grown on the thin Pt-g-C3N4 nanosheets. The photocatalytic activities of the constructed composite materials are evaluated under full solar spectrum irradiation condition including water splitting, CO2 photoreduction, and benzene to phenol conversion. The WOx/Pt-g-C3N4 nanosheet heterostructures with optimized preparation condition and without adding any co-catalyst reveals enhanced H2 generation (5267 μmolg−1h−1) and CO2 photoreduction (5.89 and 3.12 μmolg−1h−1 for CO and CH4 conversion rate, respectively), as well as improved benzene to phenol conversion (89.0%) and selectivity (98.2%). The presence of Pt clusters in the heterostructures improves charge transport in-between g-C3N4 and WOx, thus enhances the charge separation efficiency of the composite material. Detailed photocatalytic mechanisms are discussed on the alteration from S-scheme WOx/g-C3N4 heterostructure to Z-scheme WOx/Pt-g-C3N4 heterostructure.

Harmonious Heterointerfaces Formed on 2D‐Pt Nanodendrites by Facet‐Respective Stepwise Metal Deposition for Enhanced Hydrogen Evolution Reaction

AbstractThe performance of nanocrystal (NC) catalysts could be maximized by introducing rationally designed heterointerfaces formed by the facet‐ and spatio‐specific modification with other materials of desired size and thickness. However, such heterointerfaces are limited in scope and synthetically challenging. Herein, we applied a wet chemistry method to tunably deposit Pd and Ni on the available surfaces of porous 2D−Pt nanodendrites (NDs). Using 2D silica nanoreactors to house the 2D‐PtND, an 0.5‐nm‐thick epitaxial Pd or Ni layer (e‐Pd or e‐Ni) was exclusively formed on the flat {110} surface of 2D−Pt, while a non‐epitaxial Pd or Ni layer (n‐Pd or n‐Ni) was typically deposited at the {111/100} edge in absence of nanoreactor. Notably, these differently located Pd/Pt and Ni/Pt heterointerfaces experienced distinct electronic effect to influence unequally in electrocatalytic synergy for hydrogen evolution reaction (HER). For instance, an enhanced H2 generation on the Pt{110} facet with 2D‐2D interfaced e‐Pd deposition and faster water dissociation on the edge‐located n‐Ni overpowered their facet‐located counterparts in respective HER catalysis. Therefore, a feasible assembling of the valuable heterointerfaces in the optimal 2D n‐Ni/e‐Pd/Pt catalyst overcame the sluggish alkaline HER kinetics, with a catalytic activity 7.9 times higher than that of commercial Pt/C.

Harmonious Heterointerfaces Formed on 2D-Pt Nanodendrites by Facet-Respective Stepwise Metal Deposition for Enhanced Hydrogen Evolution Reaction.

The performance of nanocrystal (NC) catalysts could be maximized by introducing rationally designed heterointerfaces formed by the facet- and spatio-specific modification with other materials of desired size and thickness. However, such heterointerfaces are limited in scope and synthetically challenging. Herein, we applied a wet chemistry method to tunably deposit Pd and Ni on the available surfaces of porous 2D-Pt nanodendrites (NDs). Using 2D silica nanoreactors to house the 2D-PtND, an 0.5-nm-thick epitaxial Pd or Ni layer (e-Pd ore-Ni) was exclusively formed on the flat {110} surface of 2D-Pt, while a non-epitaxial Pd or Ni layer (n-Pd or n-Ni) was typically deposited at the {111/100} edge in absence of nanoreactor. Notably, these differently located Pd/Pt and Ni/Pt heterointerfaces experienced distinct electronic effect to influence unevenly in electrocatalytic synergy for hydrogen evolution reaction (HER). For instance, an enhanced H2 generation on the Pt{110} facet with 2D-2D interfacede-Pddeposition and faster water dissociation on the edge-locatedn-Ni overpowered their facet-located counterparts in respective HER catalysis. Therefore, a feasible assembling of the valuable heterointerfaces in the optimal 2D n-Ni/e-Pd/Pt catalyst overcame the sluggish alkaline HER kinetics, with a catalytic activity 7.9 times higher than that of commercial Pt/C.

A facile synthesis of sub-10 nm Ni2P/g-C3N4 photocatalytic composite with ohmic contact for clean H2-energy generation under visible light irradiation

It is very attractive to find a cheap and efficient cocatalyst for enhancing the H2 generation of graphitic carbon nitride (CN) under visible light. To achieve that, we proposed a novel two-step method to deposit sub-10 nm metallic Ni2P particles on the surface of CN sheets for a maximized interfacial contact. Characteristic results confirmed the establishment of ohmic heterojunction upon Ni2P-modification of CN, which deemed to be an effective measure to alleviate photo-charges recombination. In addition to facilitating spatial separation of charges, Ni2P could also enhance the optical properties of CN while reducing its impedance for interfacial electron shuttling. Better still, the P-end of Ni2P is highly electronegative, offering desirable H+-capturing capability for enhanced H2 generation. These give rise to an improved H2 production of Ni2P/CN composite, optimally at 645.3 μmol g−1·h−1 as compared to immeasurable H2 yielded by the pristine CN. Such photocatalytic performance is even comparable to the Pt-modified CN photocatalyst (640.6 μmol g−1·h−1). In recyclability test, a notable activity suppression of 33.17% was recorded after four reaction cycles. This can be ascribed to the pronounced photo-corrosion of the Ni2P cocatalyst during photoreaction. Nonetheless, a remarkably high H2 generation (1328.6 μmol g−1 in 3 h) was still attained at 4th cycle. This justifies the effectiveness of our synthesized Ni2P cocatalyst in enhancing H2 generation of CN under visible light irradiation.

Ti3C2/Mn0.5Cd0.5S composite photocatalyst for enhanced H2 generation

In this paper, Ti3C2/Mn0.5Cd0.5S (TCMCS) photocatalysts were synthesized through a hydrothermal process. As-prepared samples were characterized through XRD, TEM, XPS, PL and other methods. Due to intimate contact between Mn0.5Cd0.5S (MCS) nanoparticles and Ti3C2 interface, photoinduced electrons could availably transmit from MCS to Ti3C2, promoting the transfer of photoinduced charge. Meanwhile, TCMCS exhibited better light absorption capacity and lower hydrogen precipitation overpotential. When TCMCS was applied for splitting water to H2, compared with bare MCS (543.31 μmol h−1 g−1), the prepared TCMCS composites showed a higher hydrogen precipitation rate (2046.25 μmol h−1 g−1), and stable hydrogen precipitation ability. Therefore, in the field of developing efficient photocatalysts for hydrogen precipitation, this work brings a reference.

Sulfur vacancy and p-n junction synergistically boosting interfacial charge transfer and separation in ZnIn2S4/NiWO4 heterostructure for enhanced photocatalytic hydrogen evolution

Constructing a p-n heterojunction with vacancy is advantageous for speeding up carrier separation and migration due to the synergy of the built-in electric field and electron capture of the vacancy. Herein, a sulfur vacancy riched-ZnIn2S4/NiWO4 p-n heterojunction (VZIS/NWO) photocatalyst was rationally designed and fabricated for photocatalytic hydrogen evolution. The composition and structure of VZIS/NWO were characterized. The existence of sulfur vacancy was confirmed through X-ray photoelectron spectroscopy, high-resolution transmission electron microscope, and electron paramagnetic resonance technology. The p-n heterojunction formed by ZnIn2S4 and NiWO4 was proved to provide a convenient channel to boost interfacial charge migration and separation. By reducing the band gap, the vacancy engineer can improve light absorption as well as serve as an electron trap to improve photo-induced electron-hole separation. Benefiting from the synergy of p-n heterojunction and vacancy, the optimal VZIS/NWO-5 catalyst exhibits dramatically enhanced H2 generation performance, which is about 10-fold that of the pristine ZnIn2S4. This work emphasizes the synergy between p-n heterojunction and sulfur vacancy for enhancing photocatalytic hydrogen evolution performance.

Construction of PdS@MIL-125-NH2@ZnS type-II heterostructure with efficient charge separation for boosted photocatalytic hydrogen evolution

A new photocatalyst, PdS@NH2-MIL-125(Ti)@ZnS (PdS/M125/ZnS) heterojunction is fabricated for photocatalytic H2 generation for the first time, where PdS nanoparticles are anchored in the pore of M125 by utilizing its confinement effect, and the ZnS is closely wrapped on the surfaces of the MOFs. The optimal photocatalyst exhibits a significantly enhanced H2 generation rate of 1164.2 μmol/g/h, while the pure M125 only displays a H2 generation rate of 16.7 μmol/g/h. The resultant improvement can be ascribed to the following comprehensive advantages. The hierarchical structure built by PdS, M125, and ZnS can form lots of intimate interfaces, offer abundant sites for reaction, and smooth channels for charge carriers due to the porous characteristics of MOFs. Moreover, M125 and ZnS with inner defect levels form an analogous type-II heterojunction assisted by PdS co-catalyst, which greatly promotes charge separation. This work may supply a new avenue to design MOFs photocatalysts for energy conversion.

Boosting Hydrogen Evolution Reaction by Phase Engineering and Phosphorus Doping on Ru/P-TiO2.

Synergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster anchored on a trace P-doped defective TiO2 substrate (Ru/P-TiO2 ) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C-like geometric activity and an excellent mass activity of 9984.3 mA mgRu -1 at -0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2 , respectively. Experimental and theoretical studies indicated that using a rutile-TiO2 -crystal-phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile-TiO2 facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+ with P5+ enhanced H2 generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity.

Boosting Hydrogen Evolution Reaction by Phase Engineering and Phosphorus Doping on Ru/P‐TiO2

AbstractSynergistic optimization of the elementary steps of water dissociation and hydrogen desorption for the hydrogen evolution reaction (HER) in alkaline media is a challenge. Herein, the Ru cluster anchored on a trace P‐doped defective TiO2substrate (Ru/P‐TiO2) was synthesized as an electrocatalyst for the HER; it exhibited a commercial Pt/C‐like geometric activity and an excellent mass activity of 9984.3 mA mgRu−1at −0.05 V vs. RHE, which is 34.3 and 18.7 times higher than that of Pt/C and Ru/TiO2, respectively. Experimental and theoretical studies indicated that using a rutile‐TiO2‐crystal‐phase substrate enhanced the HER activity more than the anatase phase. Rich surface oxygen vacancies on rutile‐TiO2facilitated the adsorption and dissociation of water, while the partial substitution of Ti4+with P5+enhanced H2generation by facilitating hydrogen spillover from the Ru site to the surface P site, synergistically enhancing the HER activity.

Intensified effect of K adhering to hematite involved in the sulfurous chemical looping gasification

When sulfur in petroleum coke (petcoke) converts to H2S instead of SO2, it is the resource which can be recovered by Claus process. Chemical looping gasification (CLG) is capable of achieving petcoke conversion and sulfur recovery. To simultaneously overcome the obstacles of low gasification reactivity and improve H2 and H2S production, hematite modified by K as oxygen carrier (OC) was involved in the high-sulfur system to investigate the effect on sulfur conversion via batch fluidized bed in petcoke CLG process. K enhanced H2 generation beyond expectation because K not only improved the petcoke gasification but also enhanced the steam oxidation of deep reductive OC. Especially when using 10 % KNO3-hematite, H2 yield increased by 3.9 times as compared to 0 % K, with the carbon conversion efficiency of 99.92 % in the 22nd minute. The different K sources had a different H2 selectivity. The sulfur fate had been originally studied using K-modified hematite OC. H2S was the main phase of sulfur release and the high H2 yield also assisted H2S production. Introducing K contributed to in-situ sulfur capture forming K-Fe-S compounds in the OCs due to the deep reduction of Fe. 10 % KNO3-hematite exhibited excellent cyclic stability with a H2 volume fraction of more than 65 % in 21 cycles. Furthermore, the mechanism of hematite modified by K involved in sulfur-containing system was summarized in petcoke CLG process.

Plasmonically Enhanced Hydrogen Evolution with an Al–TiO2-Based Photoelectrode

Photoelectrochemical water splitting, as a method for producing clean hydrogen, could benefit from both plasmon-enhanced processes and the incorporation of earth-abundant materials in photoelectrode design. Here we report a n-TiO2/aluminum (Al) nanodisk/p-GaN photoelectrode sandwich device that exhibits enhanced H2 generation efficiencies due to a combination of plasmon-enhanced processes. Hot electrons generated in the illuminated Al nanodisk are injected into the conduction band of the TiO2 layer, subsequently transferring into water molecules adsorbed on the TiO2 surface, driving H2 evolution. The photocurrent densities we observe are nearly an order of magnitude higher than in an equivalent device with the Al nanodisk replaced with a Au nanodisk of the same size and are on par or better than previous reports of plasmonic photoelectrodes using Au nanoparticles in combination with cocatalyst species.

Water-Enabled H2 Generation from Hydrogenated Silicon Nanosheets for Efficient Anti-Inflammation.

As an emerging therapeutic gas, hydrogen (H2) is gifted with excellent biosafety, high tissue permeability, and radical-trapping capacity and is extensively considered as a highly promising antioxidant in clinics. However, a facile and effective strategy of H2 production for major inflammatory disease treatments is still lacking. In this study, by a facile wet-chemical exfoliation synthesis, a hydrogen-terminated silicon nanosheet (H-silicene) has been synthesized, which can favorably react with environmental water to generate H2 rapidly and continuously without any external energy input. Furthermore, theoretical calculations were employed to reveal the mechanism of enhanced H2 generation efficacy of H-silicene nanosheets. The as-synthesized H-silicene has been explored as a flexible hydrogen gas generator for efficient antioxidative stress application for the first time, which highlights a promising prospect of this two-dimensional H-silicene nanomaterial for acute inflammatory treatments by on-demand H2 production-enabled reactive oxygen species scavenging. This study provides a novel and efficient modality for nanomaterial-mediated H2 therapy.

Exploring the Polarization Photocatalysis of ZnIn2S4 Material toward Hydrogen Evolution by Integrating Cascade Electric Fields with Hole Transfer Vehicle

AbstractSluggish charge kinetics in photocatalysts and slow hole transfer in oxidation half‐reaction severely limit the photocatalytic activity of hydrogen evolution. ZnIn2S4 with an asymmetrical layered structure of [S–In]–[S–In–S]–[Zn–S] unit cell is a promising material offering asymmetrical crystal polarization to overcome the limitation; however, the polarization‐induced internal electric field by this material remains largely unexplored. Herein, the polarization‐induced internal electric field of ZnIn2S4 by engineering the polarity intensity in microscopic units is demonstrated for the first time. Specifically, ultrathin ZnIn2S4 nanosheets are employed to establish a Ni12P5/ZnIn2S4‐O (NP/ZIS‐O) system with powerful bulk and interface cascade electric field by the oxygen doping and ohmic junction. Enabled by such a design, the photogenerated electrons can rapidly migrate to NP active sites, suppressing the photogenerated electron‐hole pair recombination on ZIS‐O. To further overcome the inefficient hole transfer in oxidation half‐reaction, the preferential dehydrogenation of the α‐CH bond in benzyl alcohol is utilized as a vehicle to facilitate hole transfer. As a result, a remarkably enhanced H2 generation of 15.79 mmol g–1 h–1 is achieved on NP/ZIS‐O, which is 8.16‐fold higher than that of pristine ZnIn2S4. Meanwhile, as a value‐added oxidation product, benzaldehyde can be produced at the rate of 17.63 mmol g–1 h–1. This work presents a collaborative strategy for engineering charge behavior in photocatalysts with polarization features, and provides insights into materials design toward photocatalytic hydrogen production and organic synthesis from the angle of charge kinetics.

Energy funneling and charge separation in CdS modified with dual cocatalysts for enhanced H2 generation

Anchoring molecular cocatalysts on semiconductors has been recognized as a general strategy to boost the charge separation efficiency required for efficient photocatalysis. However, the effect of molecular cocatalysts on energy funneling (i.e., directional energy transfer) inside semiconductor photocatalysts has not been demonstrated yet. Here we prepared CdS nanorods with both thin and thick rods and anchored the conjugated molecules 2-mercaptobenzimidazole (MBI) and cobalt molecular catalysts (MCoA) sequentially onto the surface of nanorods. Transient absorption measurements revealed that MBI molecules facilitated energy funneling from thin to thick rods by the electronic coupling between thin and thick nanorods, which is essentially a light-harvesting antenna approach to enhance the charge generation efficiency in the reaction center (here the thick rods). Moreover, MBI and MCoA molecules selectively extracted photogenerated holes and electrons of CdS nanorods rapidly, leading to efficient charge separation. Consequently, CdS/MBI/MCoA displayed 15 times enhanced photocatalytic H 2 evolution (1.65 mL) than pure CdS (0.11 mL) over 3 h of illumination. The amount of H 2 evolution reached 60 mL over 48 h of illumination with a high turnover number of 26294 and an apparent quantum efficiency of 71% at 420 nm. This study demonstrates a novel design principle for next-generation photocatalysts. For CdS/MBI/MCoA, the MBI and MCoA molecules selectively extracted photogenerated holes and electrons from CdS nanorods rapidly. Additionally, the MBI molecules facilitated energy funneling from thin to thick rods, endowing CdS/MBI/MCoA elevated photocatalytic H 2 evolution.