H2 Production Activity Research Articles

Microalgae gasification over Ni loaded perovskites for enhanced biohydrogen generation

Steam gasification of microalgae upon perovskite oxide-supported nickel (Ni) catalysts was carried out for H2-rich gas production. Ni-perovskite oxide catalysts with partial substitution of B in perovskite structures (Ni/CaZrO3, Ni/Ca(Zr0.8Ti0.2)O3, and Ni/Ca(Zr0.6Ti0.4)O3) were synthesized and compared with those of the Ni/Al2O3 catalyst. The perovskite oxide supports improved Ni dispersion by reducing the particle size and strengthening the Ni-support interaction. Higher gas yields and H2 selectivity were obtained using Ni-perovskite oxide catalysts rather than Ni/Al2O3. In particular, Ni/Ca(Zr0.8Ti0.2)O3 showed the highest activity and selectivity for H2 production because of the synergetic effect of metallic Ni and elements present in the perovskite structures caused by high catalytic activity coupled with enhanced oxygen mobility. Moreover, increasing the temperature promoted the yield of gas and H2 content. Overall, considering the outstanding advantages of perovskite oxides as supports for Ni catalysts is a promising prospect for H2 production via gasification technology.

Controlled Synthesis of Nitro-Terminated Oligothiophene/Crystallinity-Improved g-C3N4 Heterojunctions for Enhanced Visible-Light Catalytic H2 Production

It is highly desired to explore closely contacted polymer semiconductor/g-C3N4 heterojunction photocatalysts with promoted photogenerated-carrier separation and extended visible-light response for efficient visible-light-driven H2 production. Here, we first synthesized the nitro-terminated oligothiophene (OTh) by the controlled copolymerization of thiophene and 2-nitrothiophene monomers, then constructed the nitro-terminated oligothiophene/crystallinity-improved g-C3N4 (OTh/g-C3N4) heterojunctions by a grinding-induced combination strategy. The ratio-optimized 20OTh5/g-C3N4 shows highly efficient H2 production activity up to 3.63 mmol h-1 g-1 under visible-light irradiation, with ∼25.9-time enhancement compared to that of g-C3N4. As verified by time-resolved photoluminescence spectra, surface photovoltage spectra, and the fluorescence spectra related to •OH amounts, the improved photocatalytic activity is due to the promoted photogenerated-carrier transfer and separation in the heterojunctions and the expanded visible-light response. It is also confirmed that the controlled OTh chain length, improved g-C3N4 crystallinity, and tight interface contact dependent on the hydrogen bonds and N···S interactions between OTh and g-C3N4 are reasonable for enhanced photogenerated-carrier separation with the electron transfer from OTh to g-C3N4. This work illustrates a feasible strategy to construct efficient polymer semiconductor/g-C3N4 heterojunction photocatalysts for solar-light-driven H2 production.

Carbon intercalated MoS2 cocatalyst on g-C3N4 photo-absorber for enhanced photocatalytic H2 evolution under the simulated solar light

Despite MoS2 being a promising non-precious-metal cocatalyst, poor electronic conductivity and low activity for hydrogen evolution caused by serious agglomeration have been identified as critical roadblocks to further developing MoS2 cocatalyst for photocatalytic water splitting using solar energy. In this work, the density functional theory calculations reveal that carbon intercalated MoS2 (C-MoS2) has excellent electronic transport properties and could effectively improve catalytic activity. The experiment results show that the prepared tremella-like C-MoS2 nanoparticles have large interlayer spacing along the c-axis direction and high dispersion because of intercalation of the carbon between adjacent MoS2 layers. Furthermore, the heterostructure photocatalyst of C-MoS2@g-C3N4 formed by loading the cocatalyst of C-MoS2 onto g-C3N4 nanosheets exhibits the H2 evolution rate of 157.14 μmolg−1h−1 when containing 5 wt% C-MoS2. The high photocatalytic H2 production activity of the 5 wt% C-MoS2@g-C3N4 can be attributed to the intercalated conductive carbon layers in MoS2, which leads to efficient charge separation and transfer as well as increased activities of the edge S atoms for H2 evolution. We believe that the C-MoS2 will offer great potential as a photocatalytic H2 evolution reaction cocatalyst with high efficiency and low cost.

Fabrication of Porous Hydrophilic CN/PANI Heterojunction Film for High-Efficiency Photocatalytic H2 Evolution

The modulation of surface wettability and morphology are essential to optimize the photocatalytic H2 evolution activity of graphitic carbon nitride (CN)-based photocatalysts. In this work, the porous hydrophilic CN/PANI heterojunction film was prepared via interfacial polymerization and loaded on a porous PCL substrate. The construction of the type-II CN/PANI heterojunction enabled an overall spectrum response and the efficient separation and transportation of photoexcited charge carriers. The fabricated CN/PANI solid-state film in comparison with its powder counterpart elevated the utilization efficiency and maintained the long-term stability of photocatalyst. The porous morphology and hydrophilic surface increased the surface area and enhanced the surface wettability, favoring water-molecule adsorption and activation. The as-prepared CN/PANI heterojunction film exhibited photocatalytic H2 production activity up to 3164.3 μmol·h−1·g−1, which was nearly 16-fold higher than that of pristine CN (569.1 μmol·h−1·g−1).

In situ growth of 1T-WS2 on ultrathin Ti3C2Tx as a hybrid cocatalyst for enhancing the photocatalytic activity of CdS

Accelerating charge transfer and separation is the core mission of promoting photocatalytic H2 production activity. Here, the hybrid cocatalyst Ti3C2Tx/1T-WS2 is synthesized by in situ growth of 1T-WS2 on the ultrathin Ti3C2Tx surface using a solvothermal method for enhancing the photocatalytic activity of CdS. The difference in CB potentials between CdS and 1T-WS2 results in the rapid migration of photogenerated electrons from CdS to 1T-WS2. More importantly, because of the intimate Schottky interfacial contact between Ti3C2Tx and 1T-WS2, the electrons on the 1T-WS2 further rapidly transfer to the surface of Ti3C2Tx, thereby enhancing the separation efficiency of photogenerated electrons. Compared with the single Ti3C2Tx (4.66 mmol∙g−1∙h−1) and 1T-WS2 (10.65 mmol∙g−1∙h−1), the hybrid Ti3C2Tx/1T-WS2 cocatalyst (12.39 mmol∙h−1∙g−1) has more excellent catalytic hydrogen evolution performance. The apparent quantum efficiency (AQE) Ti3C2Tx/1T-WS2/CdS at λ = 420 nm reaches 50.9%. This work is helpful to understand the mechanism of the hybrid cocatalyst to improve charge separation.

Facile preparation of carbon nitride by binary eutectic KNO3/KCl molten salt and its photocatalytic performance evaluation

A facile molten salt-assisted heat-treated carbon nitride via binary eutectic KNO3/KCl was successfully developed. The as-prepared photocatalyst had much improved photocatalytic activity for organic matter photodegradation and H2 production.

Efficient full solar spectrum-driven photocatalytic hydrogen production on low bandgap TiO2/conjugated polymer nanostructures.

The development of photocatalysts that can utilize the entire solar spectrum is crucial to achieving efficient solar energy conversion. The utility of the benchmark photocatalyst, TiO2, is limited only to the UV region due to its large bandgap. Extending the light harvesting properties across the entire spectrum is paramount to enhancing solar photocatalytic performance. In this work, we developed low bandgap TiO2/conjugated polymer nanostructures which exhibit full spectrum activity for efficient H2 production. The highly mesoporous structure of the nanostructures together with the photosensitizing properties of the conjugated polymer enabled efficient solar light activity. The mesoporous TiO2 nanostructures calcined at 550 °C exhibited a defect-free anatase crystalline phase with traces of brookite and high surface area, resulting in the best performance in hydrogen production (5.34 mmol g-1 h-1) under sunlight simulation. This value is higher not only in comparison to other TiO2-based catalysts but also to other semiconductor materials reported in the literature. Thus, this work provides an effective strategy for the construction of full spectrum active nanostructured catalysts for enhanced solar photocatalytic hydrogen production.

A novel 1D/2D core/shell CdS@SnS2 heterostructure for efficient piezocatalytic hydrogen evolution and pollutant degradation

A CdS@SnS2 core/shell heterostructure is constructed by in situ growth of SnS2 nanosheets on CdS nanorods for boosting piezocatalytic activity of H2 production and dye degradation.

Photothermal catalytic H2 production over hierarchical porous CaTiO3 with plasmonic gold nanoparticles

The synergistic promotion by photocatalysis and thermocatalysis is a promising approach for sustainable hydrogen (H2) production. Herein, we rationally design a perovskite-based catalyst with three-dimensionally ordered macroporous structure (3DOM CaTiO3-Au) for photothermal catalytic H2 production from different substrates. The hierarchical 3DOM structure facilitates light harvesting and mass diffusion of the substrates, while the gold nanoparticles (Au NPs) promote charge separation. The photogenerated and hot electrons are oriented accumulated on the surface of Au NPs. The non-metallic gold species [Au(I)] show more activity for H2 evolution. As a result, 3DOM CaTiO3-Au exhibits excellent activity for H2 production from glycerol and other substrates with hydroxyl groups. The present work demonstrates a feasible approach to improve sustainable H2 production by rationally designing and fabricating efficient photothermal catalysts.

Electrocatalytic hydrogen production activity with a copper(ii)-dipyridylamine complex in acidic water

A water-stable and structurally characterised earth-abundant copper(ii)-dipyridylamine complex was synthesized and evaluated for electrocatalytic H2 production activity in water using acetic acid as a proton source.

Enhancing the photo-driven seawater splitting performance of hierarchical TiO2 through rich surface hydroxyl and oxygen vacancy design

Hierarchical TiO2 nanofibers exhibit excellent H2 production activity and stability in seawater owing to the enhanced charge transfer and fast H+ adsorption by the synergistic effects of surface hydroxyls and oxygen vacancies.

Enhanced photocatalytic hydrogen production activity of Ni modified TiO2/GO nanosheet composites

Ni modified TiO2/GO nanosheet composites were prepared using a hydrothermal method, and exhibited an enhanced photocatalytic H2-production activity.

Photobio-electrocatalytic production of H2 using fluorine-doped tin oxide (FTO) electrodes covered with a NiO-In2S3 p-n junction and NiFeSe hydrogenase

Clean energy vectors are needed towards a fossil fuel-free society, diminishing both greenhouse effect and pollution. Electrochemical water splitting is a clean route to obtain green hydrogen, the cleanest fuel; although efficient electrocatalysts are required to avoid high overpotentials in this process. The combination of inorganic semiconductors with biocatalysts for photoelectrochemical H2 production is an alternative approach to overcome this challenge. N-type semiconductors can be coupled to a co-catalyst for H2 production in the presence of a sacrificial electron donor in solution, but the replacement of the latter with an electrode is a challenge. In this work we attach a NiFeSe-hydrogenase with high activity for H2 production with the n-type semiconductor indium sulfide, which upon visible irradiation is able to transfer its excited electrons to the enzyme. In order to enhance the transfer of the generated holes towards the electrode for their replenishment, we have explored the inclusion of a p-type material, NiO, to induce a p-n junction for H2 production in a photoelectrochemical biocatalytic system in absence of sacrificial reagents.

“O-S” Charge Transfer Mechanism Guiding Design of a ZnIn2S4/SnSe2/In2Se3 Heterostructure Photocatalyst for Efficient Hydrogen Production

The purposeful regulation of the charge transfer pathway is of great significance for efficient H2 evolution activity. Herein, a ZnIn2S4 (DZIS)-based heterostructure of ZnIn2S4/SnSe2/In2Se3 (DZIS/SnSe2/In2Se3) was fabricated in which the “O-S” charge transfer was realized by constructing an Ohmic-like junction between DZIS and SnSe2, as well as a Schottky-like junction between SnSe2 and In2Se3. The Ohmic-like junction promoted the electrons in DZIS to transfer to SnSe2, whereas the Schottky-like junction accelerated the holes in In2Se3 to transfer to SnSe2. Benefiting from the peculiar “O-S” charge transfer, a large number of highly active photogenerated electrons were resolved in the conduction band of In2Se3, which contributed to the enhancement of H2 production activity. Under visible light irradiation, the optimized DZIS/SnSe2/In2Se3 exhibits a H2 evolution rate of 86.91 mmol·h–1·g–1 and an apparent quantum efficiency of 20.97% at 420 nm. This work reports an advanced prototype for realizing the desired charge transfer route through artificial heterointerface designing in an all-in-one photocatalyst.

Plasma surface treatment facilitated visible light-driven H2 production over TiO2

TiO2 precursors were treated by plasma technology in three atmospheres (N2, Ar, H2). Interstitial N-doping can be facilely realized in N2 atmosphere, the light absorption range of N2-TiO2 is enlarged, and the surface oxygen vacancies (OVs) are significantly increased. Surface OVs enhance the efficient separation of photogenerated e−/h+ pairs in TiO2. The microscopic oxide layer on the surface of TiO2 is destroyed, bringing about Ti3+ defects and formation of more surface OVs in H2 and Ar atmosphere. Ti3+ defects, high concentration of surface OVs and the Ti3+-OVs defect energy level significantly reduce the photogenerated electron excitation energy. The photocatalytic H2 production activity of TiO2 treated via plasma technique in the different atmospheres was evaluated under visible light irradiation. Consequently, the H2 production efficiency on N2-TiO2 is 103.6 umolh−1 g−1, which is 2.1 times, 1.6 times, and 1.3 times of that on the pristine TiO2, H2-TiO2, and Ar-TiO2, respectively. The apparent quantum efficiency (AQE) of H2 generation on N2-TiO2 is 0.08%, which is 1.6 times of that over the reference TiO2 under 420 nm monochromatic light irradiation. The photocatalytic mechanisms for H2 production over all the photocatalysts were discussed according to a series of characterizations.

Cadmium (II) Organo Tetrakis-[1,2]-Oxathiin (CdOTOT): A 3D sandwiched frameworks with efficient hydrogen production

For over a decade, the structure, reactivity, and mechanism of graphene based photocatalysts have been of great interest for hydrogen (H2) generation. Several studies have been done on the edge side groups (ESGs) of graphene oxide (GO), but the basal plane groups (BPGs)-epoxide and hydroxide have acquired far less attention. This is because the GO layers are strongly held with van der waals forces as well as H-bonding which prevents the foreign body from entering inside the layers. To overcome these problems, this study presents the successful synthesis and application of four coordinated sandwiched (FCS) Cadmium (II) Organo Tetrakis-[1,2]-Oxathiin (CdOTOT) in rGO-CdS composite (A 3D sandwiched framework). Additionally, experimental outcomes have been further supported using density functional theory (DFT), which suggest that CdOTOT is more stable than its precursors as well as thermodynamically favourable. The CdOTOT shows high H2 production activity ∼ 67.5 mmol/g or 13.5 mmol/g/h in presence of 1 % Pt cocatalyst and sacrificial reagents (Na2S/Na2SO3). It is around 33 times higher than pristine CdS, and stable up to around 15 hrs without adding any cocatalyst. This mesmerising outcome is over with reported various CdS-rGO based photocatalysts. The higher activity was further explained through the proposed mechanism and observed low electronic work function of CdOTOT. This innovative and extendable (with other metals) approach provides a revolutionary impact on numerous cutting-edge research applications like photocatalysis, water splitting, solar cell, etc.

Solution combustion synthesis of CoSx, MoSx, CoSx-MoSx and their catalytic activity in H2 production from H2S decomposition

Production of hydrogen from H2S is desirable and can meet partly the ever-increasing demand on cheaper and greener hydrogen as a cleaner energy resource since it makes better use of H2S than the various Claus processes. Medium temperature effective catalysts for H2S decomposition would help developing a sulfur looping process to overcome the thermodynamic limitation for H2S decomposition. However, developing such medium temperature catalyst for direct H2S decomposition is still a great challenge. This work adapts solution combustion synthesis (SCS) method to synthesize oxide and sulfide of molybdenum and cobalt with fine crystalline and their activities in H2S decomposition were investigated. The in-situ sulfurization with thiourea in SCS process leads to higher surface area and higher activity of the resultant catalysts. The presence of CoSx enchances the activity of MoSx in H2S decomposition. The H2S decomposition activity of the CoSx-MoSx composite is higher than that of each single component one. The H2S decomposition kinetics analysis shows that an activation energy of 43.3 kJ/mol was achieved on 20%CoSx-MoSx which is much lower than that reported in literatures.

Incorporating Ni-Polyoxometalate into the S-Scheme Heterojunction to Accelerate Charge Separation and Resist Photocorrosion for Promoting Photocatalytic Activity and Stability.

The emerging polyoxometalate (POM) nanomaterials are transition metal oxygen anion clusters with d0 electronic configurations, which could be attractive and potential photocatalysts. Hence, a nickel (Ni)-substituted polyoxometalate K6Na4[Ni4(H2O)2(PW9O34)2]·32H2O (Ni4POM)-incorporating step (S)-scheme heterojunction was developed to promote photocatalytic activity and stability in H2 and H2O2 production. The multielectron transfer through variable valence metal centers in Ni4POM would facilitate the recombination of invalid charges through the S-scheme pathway. Moreover, incorporating Ni4POM into the S-scheme heterojunction can broaden the light absorption range and meanwhile lead to resistance to photocorrosion to promote the optical and chemical stability of Cd0.5Zn0.5S (CZS). The optimized CZSNi-70 exhibited a H2 evolution rate of 42.32 mmol g-1 h-1 under visible-light irradiation with an apparent quantum yield of 32.27% at 420 nm and a H2O2 production rate of 295.4 μmol L-1 h-1 under 420 nm light-emitting diode irradiation. This work can provide a new view for the development of transition metal-substituted POM-based stable and efficient S-scheme photocatalysts.

Boosting interfacial S-scheme charge transfer and photocatalytic H2-production activity of 1D/2D WO3/g-C3N4 heterojunction by molecular benzene-rings integration

A novel benzene-ring engineered 1D/2D WO3/g-C3N4 S-scheme photocatalyst (BCNW) was rationally designed and successfully synthesized by the electrostatic self-assembly method. Experimental and Density Functional Theory results reveal that the integration of molecular benzene-ring in the framework of g-C3N4 can not only narrow its bandgap and accelerate charge separation by forming a mid-state at the top of its valence band but more importantly open up a new additional bridge for speeding up the interfacial S-scheme charge transfer in BCNW. Benefitting from those multiple positive effects of benzene-ring integration, as expected, BCNW S-scheme photocatalysts show superior photocatalytic H2-production activity and reach 2971 μmol h–1 g–1 under visible-light illumination, which is 3.35 times WO3/g-C3N4 S-scheme photocatalyst without benzene-ring integration. This work supplies an innovative strategy for the design of a high-efficiency S-scheme photocatalytic system by constructing a facile and additional molecular charge transfer channel at the interface.

Oxygen vacancy and p-n junction synergistically boosting photocatalytic hydrogen evolution in alkaline solution for a 2D lamellar Co3O4/K7HNb6O19

The exploration of efficient alkaline hydrogen evolution photocatalysts is very meaningful in overall water splitting due to the fact that the high O2 evolution performance is usually obtained under alkaline conditions. Herein, we successfully prepared a kind of photocatalysts with excellent H2 production activity in an alkaline environment by combining Lindqvist-type polyoxoniobate K7HNb6O19 with Co3O4. The hydrogen production performance of the optimal sample could reach 5394.17 μmol g−1 under highly alkaline conditions. The superior H2 evolution activity is mainly endowed by p-n heterojunction creating an internal-built electric field on the interface of the two semiconductors, which realizes the effective spatial separation of electron-hole pairs. Simultaneously, the increased oxygen vacancies and lamellar structure of catalysts also respectively endow samples with a high H2O adsorption capacity and efficient photoinduced carrier separation rate. The work will be instructive for designing high-efficiency and stable HER catalyst in alkaline conditions for practical applications.