Highest H2 Production Research Articles

PtOx deposited Fe3O4-ZnO/TiO2 nanocomposites for photocatalytic H2 production under visible light

In this work, TiO2 nanotubes, Fe3O4-ZnO, nanocomposites of Fe3O4-ZnO and TiO2 were synthesized by varying the amount (5, 10 and 15 wt%) of Fe3O4-ZnO. The obtained nanocomposites were decorated with PtOx (1.0 wt%) nanoparticles via green synthesis method using Chamomile flowers extract. The synthesized samples were thoroughly characterized by XRD, SEM, HRTEM, FT-IR, DRUV-vis, PL N2-physisorption and XPS spectroscopy measurements. The XRD, FT-IR, XPS spectroscopy and microscopy results revealed the existence of strong interaction between Fe3O4-ZnO and TiO2 nanotubes. Deposition of PtOx on the surface of TiO2, Fe3O4-ZnO and Fe3O4-ZnO/TiO2 nanocomposite samples resulted in a decrease in the bandgap to 3.26 eV, 1.90 eV and 1.80 eV respectively. Further, Fe3O4-ZnO/TiO2 nanocomposites exhibited relatively high surface area (95 m2g−1) and pore volume (0.174 cm3g−1) than Fe3O4-ZnO sample. The presence of surface PtOx species resulted in delaying the recombination of e-/h+ pairs. Different reaction conditions such as pH of solution, methanol/H2O ratio and catalyst mass were optimized to obtain high photocatalytic H2 production. The highest photocatalytic H2 production [485μmol/(gcatalysth)−1] was observed in case of Pt@Fe3O4-ZnO/TiO2-3 catalyst under visible light irradiation at 80 °C. In addition, the synthesized PtOx deposited nanocomposite materials could be separated easily from the reaction mixture and reused five times without considerable loss of photocatalytic activity.

Molecular Engineering in D-π-A-A-Type Conjugated Microporous Polymers for Boosting Photocatalytic Hydrogen Evolution.

Conjugated microporous polymer (CMP) photocatalysts with donor-π-acceptor (D-π-A) or donor-acceptor (D-A) structures have garnered great attention for solar-driven hydrogen generation because of their inherent charge separation nature and high surface area. Herein, we design a series of D-π-A-A-type CMP photocatalysts to uncover the influence of the content of the dibenzo[b,d]thiophene-S-S-dioxide (BTDO) acceptor on the photocatalytic activity. The results demonstrate that the acceptor content in the D-π-A-A-type CMP photocatalysts affects the electronic structure, the availability of reaction sites, and the separation between light-generated electrons and holes, which mainly determine the photocatalytic performance for H2 release. Benefiting from the synergy of light absorption, hydrophilicity, and active sites, the bare polymer PyT-BTDO-2 with an optimized BTDO content exhibits a high H2 production rate of 230.06 mmol h-1 g-1 under simulated sunlight, manifesting that the strategy of D-π-A-A structural design is efficacious for boosting the photocatalytic performance of CMP photocatalysts.

Recent advances and prospects in high purity H2 production from sorption enhanced reforming of bio-ethanol and bio-glycerol as carbon negative processes: A review

Hydrogen has wide applications in the chemical and petroleum industries and is a clean energy carrier for electrical power generation and transportation. However, in current industries, H2 is mainly obtained from the steam reforming of natural gas and coal gasification, which resulted in huge emissions of CO2 (greenhouse gasses) and high energy consumption for H2 purification. Hence, developing H2 production technology in sustainable routes with low carbon emissions is still urgent. Sorption-enhanced steam reforming of bio-ethanol (SESRE) and sorption-enhanced steam reforming of bio-glycerol (SESRG), which coupled in-situ CO2 capture with the steam reforming of bio-ethanol or bio-glycerol, are promising strategies to yield high purity of H2 without emitting CO2 into the atmosphere. In these strategies, high purity of H2 can be produced when the high energy-consumption process such as H2 purification is avoided; besides, negative CO2 emissions can be achieved when the captured CO2 is used or sequestered. The catalysts play a pivotal role in the steam reforming processes, and the dual-functional materials (DFMs) are well regarded as the most promising solid catalysts that contribute to high-purity H2 production and CO2 capture. Thus far, there is no criterion to guide DFMs engineering for H2 generation in the SESRE and SESRG processes. Hence, in this work, a comprehensive review of the recent advances and prospects in SESRE and SESRG is presented, which provides constructive insight into the development of SESRE and SESRG technology. The optimum operating conditions in the SESRE and SESRG systems are analyzed via thermodynamics and kinetics, and the recent research progress of the DFMs is critically reviewed. Furthermore, the reforming reaction pathways and reaction mechanisms were discussed to improve the understanding of DFMs design. Finally, the prospect and challenges in the SESRE and SESRG strategies are outlooked.

Integrated biohydrogen production and dairy manure wastewater treatment via a microalgae platform

The present study aimed to investigate the feasibility of sustainable biohydrogen production from dairy manure wastewater using a microalgae platform to achieve simultaneous wastewater treatment and clean energy production. Compared to single-stage microalgae cultivation, two-stage cultivation of indigenous wastewater bacteria and carbohydrate-rich microalgae Chlorella vulgaris ESP-6 achieved satisfactory removal of nutrients and chemical oxygen demand. The resulting biomass, with high carbohydrate content (48.8 ± 2.3%), was used as alternative feedstock for biohydrogen production by Clostridium butyricum CGS5 via dark fermentation after thermal acid pretreatment. The implementation of an automatic pH control strategy significantly promoted H2 generation, resulting in a hydrogen yield of 211 mL/g VS and a maximum productivity of 391.1 mL/L/h. To the best of our knowledge, this is the first integrated study of dairy manure wastewater treatment and biohydrogen production with high H2 yield and productivity comparable to those reported in the literature.

Discovering a Single‐Atom Catalyst for CO2 Electroreduction to C1 Hydrocarbons: Thermodynamics and Kinetics on Aluminum‐Doped Copper

AbstractThe electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a potential option to achieve carbon neutrality. Although copper (Cu) shows the highest activity for the CO2 reduction reaction (CO2RR) to hydrocarbons among metals, high reaction overpotentials and significant H2 production limit its use. We investigate single‐atom alloys (SAAs) of ten metals (Ag, Au, Fe, Ir, Ni, Pd, Pt, Rh, Ru, Al) on Cu(111), which is the most‐favored facet on Cu for methane production, using density functional theory. We examined the dopants’ ability to lower the free energy of the elementary reaction, *CO to *CHO, which is the potential‐determining step (PDS). Out of the SAAs studied, only Al‐doped Cu demonstrated a lowering of the PDS free energy. Additionally, weaker adsorption energies of *CO and *H on Al−Cu(111) suggest a preference for C1 hydrocarbons and inhibition of H2 evolution. Finally, activation barrier calculations for the PDS on Al−Cu(111) involving an explicitly hydrated proton indicated better intrinsic activity for C1 hydrocarbons compared to pure Cu(111). We also confirmed the stability of Al−Cu SAA compared to small Al clusters. Through a comprehensive study of both thermodynamics and kinetics, our study presents Al−Cu SAA as a promising catalyst for CO2 electroreduction to C1 hydrocarbons.

Anaerobic co-digestion of food waste, bio-flocculated sewage sludge, and cow dung in CSTR using E(C2)Tx synthetic consortia

In the current study, a E(C2)Tx synthetic consortia was tested for anaerobic co-digestion of food waste (FW), bio-flocculated sewage sludge (BFS)/ raw wastewater (RW) and cow dung (CD) at varying proportions in 0.25 L and 6.5 L mesophilic continuously stirred tank reactors. Anaerobic co-digestion of FW with CD and RW at the ratio of 1:1:8 in 0.25 L batch-reactor with E(C2)Tx inoculum resulted in the highest H2 production with least CO2 release. The microbial dynamics of FW:CD:RW samples were studied using 16S metagenomic sequencing which indicated a predominance of hydrolysing microbes at the end point of the digestion cycle. Subsequently, the experiments were scaled up in two continuous digesters, namely, R1 (fed with 50% FW and 50% BFS) and R2 (fed with 2% FW and 98% BFS) with 6.5 L working volume at 2.5 g VS L−1D−1 organic loading rate (OLR) for 120 days. The highest VFA production of 19,183 mg L−1 and 3,265 mg L−1 with maximum bio-methane yield of 142.21- and 225.03-mL CH4g−1 VSadded were recorded in reactors R1 and R2, respectively. In addition, a numerical analysis was conducted to visualize the mixing and temperature distribution within the digesters, and the velocity and temperature profiles were obtained using Ansys Fluent.

Synergistic integration of MXene nanosheets with CdS@TiO2 core@shell S-scheme photocatalyst for augmented hydrogen generation

In order to ensure continuous and stable production of hydrogen (H2), the development of hierarchical nanostructures within a few-layer Mxene nanosheet, incorporating an ultrathin TiO2 shell material, is essential. This shell material plays a crucial role in maintaining the long-term stability of the core and preventing photo-corrosion, thus enabling uninterrupted H2 generation. To evaluate their potential as visible-driven photocatalysts for high H2 production, we conducted a comparative analysis of CdS cores covered with three different shell transition metal oxides (TiO2@NiO@ZnO), supported by Mxene. Structural and morphological characterizations through XRD and TEM confirmed the formation of pure CdS@TiO2@NiO@ZnO core–shell nanostructures, characterized by spherical shapes with a core diameter of 187 nm and a shell thickness of 19.2 nm. XPS experiments demonstrated the structural integrity of the individual elements within the nanocomposite, existing in their respective oxidation states within the core@shell structure. The hierarchical nanostructure exhibited optical characteristics with an absorption edge ranging from 480 to 580 nm. Among the three different shell materials, TiO2 displayed the highest photocatalytic activity under visible light irradiation, followed by NiO and ZnO. Based on our findings, the CdS@TiO2 core@shell photocatalyst supported by Mxene exhibited the highest efficiency, with a production rate of 16.2 mmol.h−1.g-1cat. This can be attributed to enhanced charge separation, the spatial distribution of carriers, and favorable structural properties. Our DFT calculations further supported the efficacy of coupling Mxene with CdS/TiO2, as it facilitated efficient water splitting, with CdS favoring H2O dissociation and Mxene favoring HER. These results highlight the potential of developing highly efficient photocatalysts for water splitting by integrating Mxene with CdS/TiO2. Additionally, The prepared CDTM (Mxene@CdS/TiO2) photocatalyst existing S-scheme heterojunction for efficient water splitting. This underscores the system's effective functioning across diverse sceneries, Overall, our study presents a feasible and effective strategy for constructing an S-scheme heterojunction system that utilizes photo charge carrier separation to enhance the utilization and conversion of solar energy.

Highly efficient releasing of hydrogen from aqueous-phase reforming of methanol over Cu-SP/Al2O3–ZnO catalyst by carbon layer encapsulated hierarchical porous microsphere strategy

Highly efficient releasing of hydrogen by aqueous-phase reforming of methanol (APRM) is of great significance to promote the development of stationary and mobile H2 power supply for polymer electrolyte membrane fuel cells (PEMFCs). However, highly active catalysts with excellent performance of in situ releasing H2 from APRM still face challenges. Herein, we report a Cu-SP/Al2O3–ZnO (Cu-SP/AZ) catalyst prepared by carbon layer encapsulated hierarchical porous microsphere strategy, which enhanced Cu dispersion (52.8 wt% loading, ∼5 nm particle size) on Al2O3–ZnO (AZ) microsphere. The proposed catalyst exhibited high H2 production rate (base-free) of 64.23 μmolH2/gcat/s at 210 °C, which was nearly the same as that of 20% Pt/C catalyst (63.86 μmolH2/gcat/s) and 2.6-fold higher than that of commercial CuO/ZnO/Al2O3 catalyst (24.62 μmolH2/gcat/s). The characterization results demonstrated that its high activity in APRM could be ascribed to the strategy of carbon layer encapsulated hierarchical porous microsphere as well as coordination of hydroxyl functional group of SP with Cu2+.

Construction of multi-interfacial charge transfer paths in the NiS/CdS@CuS composite for efficient and broadband visible light photocatalytic H2 production

Broad-spectrum response and high charge separation are two important prerequisites and also challenges for a photocatalyst to achieve excellent activity. Herein, we developed a closely-contacted NiS/CdS@CuS hybrid photocatalyst to construct multi-interfacial charge transfer paths to address these two challenges. Different from previously reported, limited charge transfer for the CdS system, the synergy between photoinduced interfacial charge transfer (IFCT) at the intimate CdS/CuS interface and the superior H2 production cocatalyst (NiS) enables a multi-interfacial charge transfer, which greatly accelerates charge separation and achieves broadband H2 production. The optimal NiS/CdS@CuS composite exhibits the high H2 production activity of 25.02 mmol g−1 h−1 with an apparent quantum efficiency of 27.21% at 420 nm. This activity is even higher than that of the optimized Pt/CdS system. The creation of photoinduced IFCT allows the photocatalytic H2 production of CdS extended to 610 nm. Multiple comparison systems are constructed to understand the reaction mechanisms and highlight the importance of synergy between the three components. This work supplies a paradigm for fabricating efficient H2 production photocatalyst with both enhanced charge transfer dynamics and expanded light response range.

Interface-hydroxyl enabling methanol steam reforming toward CO-free hydrogen production over inverse ZrO2/Cu catalyst

Methanol steam reforming (MSR), as an ideal on-site hydrogen production process, is urgently calling for a groundbreaking catalyst with ultralow or even no CO formation. Herein, we report a promising inverse ZrO2/Cu catalyst system obtained by oxalate sol-gel co-precipitation and subsequent calcination/H2-reduction treatment, boosting the MSR process toward CO-free hydrogen production. The preferred ZrO2-0.1/Cu (Zr/Cu molar ratio of 0.1) achieves a high H2 productivity of 190 mmolH2 gcat−1 h−1 with undetectable CO production at 200 °C for a feed of CH3OH/H2O (1/1, mol/mol), while showing no deactivation throughout 200-h test by taking advantage of high sintering resistance of the inverse structure. As experimentally and theoretically unveiled, the specific ZrO(OH)-(Cu+/Cu) interfacial structure is formed during the reaction, offering highly reactive interfacial -OH to convert HCHO* (formed on Cu+/Cu sites from methanol; decomposable to CO/H2) into H2 and CO2 via HCOOH* intermediate. These findings will be instrumental to tailor more-advanced MSR catalysts.

Extraordinary Catalytic Performance of Nickel Half‐Metal Clusters for Light‐Driven Dry Reforming of Methane

AbstractGlobal warming and the energy shortage due to the burning of fossil fuels are two major challenges. A strategy of light‐driven catalytic dry reforming of methane (DRM) using inexhaustible solar energy has provided an effective approach to tackle these challenges. Loaded metallic Ni nanoparticles have been identified as promising catalysts as alternatives to noble metals for DRM. However, they suffer from quick deactivation caused by severe coking due to thermodynamically inevitable side‐reactions. Herein, a unique nickel half‐metal catalyst of monolayer nickel clusters stabilized by alumina is reported, with 100% atomic utilization efficiency and extraordinary catalytic performance for light‐driven DRM, dramatically different from its counterpart of conventional metallic Ni nanoparticles. It has extremely high specific H2 and CO production rates of 8572.96 and 9614.26 mmol min−1 gNi−1, more than one order of magnitude higher than those of Ni nanoparticles. No detectable coke is formed due to the alteration of kinetic processes for DRM, resulting in the inhibition of coke deposition. It is discovered that light not only significantly enhances catalytic activity, but also enables quick thermocatalytic deactivation to be durable due to the oxidation of carbon species and the desorption of strongly adsorbed CO2 and CO being dramatically promoted by light.

Construction of Tri‐Functional HOFs Material for Efficient Selective Adsorption and Photodegradation of Bisphenol A and Hydrogen Production

AbstractThis study proposes the construction of porous nanomaterial (HOFs@Fe3+) which anchors non‐noble metal ions Fe3+ onto nanoscale rod‐like hydrogen‐bonded organic frameworks (HOFs) by electrostatic and coordination interactions. The high specific surface area and the abundance of hydrogen‐bond adsorption active sites in pore structure of HOFs@Fe3+ facilitate strong interactions with the double OH in bisphenol A (BPA), resulting in the highest saturation adsorption of BPA that has been reported so far (452 mg g‐1). In addition, the ordered conjugate stacking framework structure and hydrogen bond of HOFs@Fe3+ and the variable valence properties of Fe3+ create new pathways for efficient separation of photogenerated carriers. The results show that HOFs@Fe3+ can completely adsorb and photodegrade 50 ppm BPA within 20 min, owing to the abundant hydrogen bond that acts both as adsorption sites to accelerate the mass transfer process and as catalytic sites to ensure adsorption and photodegradation can be matched synergistically. Meanwhile, the efficiency of photocatalytic H2 production by HOFs@Fe3+ reaches 21.55 mmol g‐1 h‐1 with non‐noble metal Fe3+ as co‐catalyst. This tri‐functional material with high adsorption capacity, high photodegradation efficiency, and high photocatalytic H2 production activity can be successfully used to solve the long‐standing conflict between environment and energy.

Performance of red mud oxygen carriers in chemical-looping hydrogen production using different components of plastic waste pyrolytic gas

This study proposed plastic waste-fueled Chemical-looping Hydrogen Production (CLHP) based on the concept of three-reactor chemical-looping process for the purposes of sustainable treatment of plastic wastes while producing high purity H2 and separating CO2. Oxygen carrier prepared from red mud wastes (Bauxite residues) was suggested to be circulating materials to improve combustion efficiency and H2 yield. The feasibility of using pelletized oxygen carrier prepared from red mud wastes was experimentally investigated with major components (H2, CH4 and C2H4) of plastics pyrolysis gases as fuels. The red mud oxygen carrier composed of around 38 wt% Fe2O3 and 50 wt% inert materials, and CuO-promoted oxygen carriers composed of 8.0 wt% CuO and 92 wt% red mud wastes were used. The two oxygen carriers were examined by parallel experiments, focusing on the aspects of oxygen transport, stability, hydrogen productivity and carbon deposition. Temperature and different components of plastic pyrolysis gases had significant impacts on oxygen transport behaviors; reduction tests using CH4 or C2H4 fuels suggested that the operation temperature of Fuel Reactor should be higher than 800 °C for deep reduction and high H2 productivity. CuO addition significantly promoted oxygen carrier's reactivity and oxygen transport capacity with various fuel components. The cyclic CLHP experiments, performed over 10 redox cycles with C2H4 as fuels, showed that there was only a limited degradation in oxygen carriers caused by carbon deposition and element migration. The developed oxygen carriers can meet the requirements of long-term operation for CLHP process. Carbon deposition on the oxygen carriers derived from hydrocarbon fuel cracking seemed to be inevitable, which experimentally determined in the range of 0.01–0.043 g g−1 oxygen carriers as C2H4 was used as fuels. However, the reactivity of these carbon deposits was extremely low; their initial steam-gasification temperatures were around 750 °C, much higher than the temperature used for water splitting reaction. This provides the potential opportunities for an industrial CLHP process to produce high purity H2 (>97%) despite of carbon deposits presents in Fuel Reactor.

Advanced Functional Carbon Nitride by Implanting Semi-Isolated VO2 Active Sites for Photocatalytic H2 Production and Organic Pollutant Degradation.

It is critical to facilitate surface interaction for liquid-solid two-phase photocatalytic reactions. This study demonstrates more advanced, efficient, and rich molecular-level active sites to extend the performance of carbon nitride (CN). To achieve this, semi-isolated vanadium dioxide is obtained by controlling the growth of non-crystalline VO2 anchored into sixfold cavities of the CN lattice. As a proof-of-concept, the experimental and computational results solidly corroborate that this atomic-level design has potentially taken full advantage of two worlds. The photocatalyst comprises the highest dispersion of catalytic sites with the lowest aggregation, like single-atom catalysts. It also demonstrates accelerated charge transfer with the boosted electron-hole pairs, mimicking heterojunction photocatalysts. Density functional theory calculations show that single-site VO2 anchored into the sixfold cavities significantly elevates the Fermi level, compared with the typical heterojunction. The unique features of semi-isolated sites result in a high visible-light photocatalytic H2 production of 645µmol h-1 g-1 with only 1wt% Pt. They also represent an excellent photocatalytic degradation for rhodamine B as well as tetracycline, surpassing the activities obtained from many conventional heterojunctions. This study presents exciting opportunities for the design of new heterogeneous metal oxide for a variety of reactions.

The exploration of NiO/Ca2Fe2O5/CaO in chemical looping methane conversion for syngas and H2 production

Materials used for chemical looping can be exploited to process methane in a number of ways. Using the oxygen on the solid material leads to partial or total oxidation, whilst methane cracking to carbon on the depleted solid can produce hydrogen. Regeneration of the solid to remove the cracked carbon or restore the oxygen can produce CO, H2 or a combination if CO2 or H2O is used as the oxidant. The chemical looping material separates the conversion of methane from the addition of oxygen. Materials containing sorbents like CaO can interact with the CO2 produced to shift the equilibrium in desirable ways. These materials could be utilised to configure a cyclic process that is a linear combination of DRM, SMR, and cracking with combustive regeneration of the solid. Here, a material combining a catalyst (i.e. Ni), an oxygen carrier (i.e. Ca2Fe2O5) and CaO was investigated for converting methane to syngas or hydrogen-rich gas in a cyclic DRM process. In Stage 1, methane is converted to syngas or H2 in a fluidised bed of NiO/Ca2Fe2O5/CaO, where the solid is reduced/carbonated at, e.g., 700 °C; in Stage 2, the reduced/carbonated material is regenerated at 900 °C. The thermodynamics of the Ni-Ca-Fe-O system allows Ni to stay separate from Ca2Fe2O5, meaning that CaO inhibits the formation of any mixed oxide phase of Ni and Fe. A high rate of production of syngas or H2 (depending on different phases of Stage I) was found after the NiO/Ca2Fe2O5/CaO became activated. The activated NiO/Ca2Fe2O5/CaO gave high production of syngas or H2 for over 30 cycles without material deactivation. Carbon whiskers formed during CH4 processing, and did not cause deactivation.

Insight into synergistic effect of Ti3C2 MXene and MoS2 on anti-photocorrosion and photocatalytic of CdS for hydrogen production

Facing the increasingly serious issues of energy crisis and environmental pollution, it is vital to develop efficient and durable photocatalysis systems for hydrogen (H2) production from water splitting. However, for the famous CdS-based systems, the bottleneck of poor efficiency and low stability arisen from photocorrosion has not been broken through yet. In this study, a ternary composite of CdS, MoS2 and Ti3C2 MXene with intimately contact interfaces was successfully constructed via an in situ growth method, which exhibited reinforced photocatalytic H2-production activity and increased photocorrosion resistant capability. Both of experimental characterizations and density functional theory (DFT) calculations well proved that the photogenerated holes and electrons of CdS timely migrated to Ti3C2 and MoS2, respectively. As a consequence, the optimal sample displayed a high H2 production rate of 14.88 mmol·h−1·g−1 with a lifetime of up to 78 h, and the component and structure of the composite were kept intact during the photocatalysis reaction. This work highlights the synergistic effect of the Ti3C2 MXene and MoS2 as redox dual cocatalysts on the promoted photocatalytic performance and durability of CdS, which can be anticipated to significantly enhance the commercial availability of CdS and even boost its incorporation into industrial applications.

Sorption-enhanced steam gasification of biomass for H2-rich gas production and in-situ CO2 capture by CaO-based sorbents: A critical review

The sorption-enhanced steam gasification of biomass (SEBSG) is considered a prospective thermo-chemical technology for high-purity H2 production with in-situ CO2 capture. Fundamental concepts and operating conditions of SEBSG technology were summarized in this review. Considerable industrial demonstration units have been conducted on pilot scales for large-scale availability of the SEBSG process. The influence of process parameters such as reaction temperature, Steam/Biomass (S/B) ratio, feedstock characteristics, cyclic CO2 capture capacity of CaO-based sorbents, and catalysis, were critically reviewed to provide theoretical recommendations for industrial operation. Bifunctional materials that have high catalytic activity and CO2 capture activity are crucial for ensuring high H2 production in the SEBSG. The application of density functional theory (DFT) and reactive force field molecular dynamic (ReaxFF MD) simulations on microcosmic reaction mechanisms in the SEBSG process, such as pyrolysis, WGS and reforming reactions, and CO2 capture of CaO-based materials are comprehensively overviewed. Several research gaps, like the exploitation of more efficient and low-cost bifunctional material, integrated process economics and revelation of well-rounded mechanisms, need to be filled for the following large-scale industrial applications.

Thermodynamic analysis of integrated sorption-enhanced staged-gasification of biomass and in-situ CO2 utilization by methane reforming process based on calcium looping

Sorption-enhanced H2 production using CaO promotes H2 generation by capturing CO2 in the form of CaCO3. Coupling methane reforming of CaCO3 in sorption-enhanced H2 production combines CaO regeneration with in-situ CO2 utilization. This integrated concept is expected to achieve high H2 production with CO2 capture and in-situ conversion into syngas. To evaluate the overall performance of the integrated sorption-enhanced staged-gasification of biomass and in-situ CO2 utilization by methane reforming process, the thermodynamic simulation was performed using Aspen Plus. The parameter optimization of the integrated process was carried out. The performance of the integrated process was also compared with two other processes, such as the serial sorption-enhanced staged-gasification and methane reforming process and the standalone sorption-enhanced staged-gasification process. The results exhibit that integrated methane reforming enhances H2 production from sorption-enhanced staged-gasification, because it can lower the CaO regeneration temperature and enhance the CO2 capture capacity. The integrated process produces a total gas product with H2/CO around 2, which is suitable for direct Fischer-Tropsch synthesis. Compared with the serial sorption-enhanced staged-gasification and methane reforming process, the integrated process results in 73.5% less CO2 emission and 135% more CO2 utilization. Moreover, the integrated process exhibits the higher energy conversion and exergy efficiencies than two other processes, which are as high as 74.5% and 68.6%, respectively. This work shows that the integrated process has technical and environmental potential for the utilization of biomass and CH4 to produce H2 and syngas with CO2 capture and in-situ utilization.

Cocatalyst Engineering with Robust Tunable Carbon‐Encapsulated Mo‐Rich Mo/Mo2C Heterostructure Nanoparticle for Efficient Photocatalytic Hydrogen Evolution

AbstractCocatalyst engineering with non‐noble metal nanomaterials can play a vital role in low‐cost, sustainable, and large‐scale photocatalytic hydrogen production. This research adopts slow carburization and simultaneous hydrocarbon reduction to synthesize carbon‐encapsulated Mo/Mo2C heterostructure nanoparticles, namely Mo/Mo2C@C cocatalyst. Experimental and theoretical investigations indicate that the Mo/Mo2C@C cocatalysts have a nearly ideal hydrogen‐adsorption free energy (ΔGH*), which results in the accelerated HER kinetics. As such, the cocatalysts are immobilized onto organic polymer semiconductor g‐C3N4 and inorganic semiconductor CdS, resulting in Mo/Mo2C@C/g‐C3N4 and Mo/Mo2C@C/CdS catalysts, respectively. In photocatalytic hydrogen evolution application under visible light, the Mo/Mo2C@C with g‐C3N4 and CdS can form the Schottky junctions via appropriate band alignment, greatly suppressing the recombination of photoinduced electron‐hole pairs. The surface carbon layer as the conducting scaffolds and Mo metal facilitates electron transfer and electron‐hole separation, favoring structural stability and offering more reaction sites and interfaces as electron mediators. As a result, these catalysts exhibit high H2 production rates of 2.7 mmol h−1 g−1 in basic solution and 98.2 mmol h−1 g−1 in acidic solution, respectively, which is significantly higher than that of the bench‐mark Pt‐containing catalyst. The proposed cocatalyst engineering approach is promising in developing efficient non‐noble metal cocatalysts for rapid hydrogen 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.