H2 Production Rate Research Articles

Isolation and characterization of novel bacterial strain from sewage sludge and exploring its potential for hydrogen production.

Hydrogen (H2) energy has garnered significant attention due to its numerous advantages. Nonetheless, for future commercialization, it is imperative to screen and identify strains with enhanced H2-producing capacities. In order to attain a high and consistent production performance, the conversion of biomass sources into H2 requires careful selection of the most appropriate H2-producing bacteria. This study aimed to isolate and identify a highly effective H2 producing bacteria from local sewage sludge and assess its fermentability for H2 production. The isolate was first identified by means of morphological, phenotypic, biological, and 16S rRNA investigations. A facultative anaerobe that produces H2 and is gram-negative was identified as Alcaligenes ammonioxydans strain SRAM. For the purpose of determining whether the isolate could produce H2 using glucose as the substrate, its fermentability was evaluated in 500 mL serum bottles. This strain demonstrated the ability to produce H2 from glucose under anaerobic environment, achieving a maximum H2 yield of 2.9mol H₂/mol of glucose. The highest rate of H2 production, 9.261 mmol H₂/ g dry cell weight per hr, was attained at 37°C and an initial pH of 6.8. This work effectively illustrated the use of a novel locally isolated strain in the biotechnological conversion of glucose to H2. This strategy offers an effective remedy for the world's energy instability in addition to addressing environmental issues related to industrial operations.

Efficient H2 evolution over MoS2-NiS2/g-C3N4 S-scheme photocatalyst with NiS2 as electron mediator

Low-cost transition metal sulfides are commonly utilized as photocatalysts for H2 production owing to their exceptional conductivity and superior specific surface area. In this study, MoS2-NiS2 nanoflowers with multidimensional space structure was obtained through the sulphuration reaction between S2- and NiMoO4 under Kirkendall effect during hydrothermal reaction. Subsequently, MoS2-NiS2 was loaded on the surface of g-C3N4 nanosheets using a solvent self-assembly strategy to form 3D MoS2-NiS2/g-C3N4 heterojunctions. The experimental results demonstrate that the H2 production rate of 20 wt% MoS2-NiS2/g-C3N4 reaches 22153 μmol·g-1·h-1 under a 300 W Xe lamp irradiation, which is 59.5 and 201.4-folds than MoS2-NiS2 and g-C3N4, and surpasses 20 wt% MoS2/g-C3N4 (211 μmol·g-1·h-1) and 20 wt% NiS2/g-C3N4 (6183 μmol·g-1·h-1). The XPS and Superoxide radical capture experiments demonstrate that the charge transfer between MoS2-NiS2 and g-C3N4 follows the S-scheme route, and NiS2 functions as an electron mediator, facilitating the transfer of electrons from MoS2 to g-C3N4 to consume the holes, which enhances the efficiency of H2 evolution reaction on g-C3N4. Furthermore, the S-scheme heterojunction of MoS2-NiS2/g-C3N4 with the multidimensional geometric structure can provide abundant active sites for catalytic reactions, this presents a promising approach for the development of cost-effective and high-performance g-C3N4-based heterojunctions. This work offers distinctive perspectives on the trajectory of renewable H2 energy development.

Cobalt coordinated olefin-linked covalent organic frameworks toward highly efficient photocatalytic hydrogen production

Covalent organic frameworks (COFs) have emerged as a crystalline porous materials for photocatalytic hydrogen production. However, the design of efficient COF-based catalyst for satisfactory solar-to-hydrogen energy conversion is still challenging. Here, cobalt was anchored on the bipyridine moieties in the framework of olefin-linked sp2c-COFdpy by convenient post-metalation (sp2c-COFdpy-Co). Experimental results showed that sp2c-COFdpy-Co exhibited wider visible light absorption region and quicker photogenerated e-/h+ separation efficiency than sp2c-COFdpy. Photocatalytic experiments revealed that sp2c-COFdpy-Co was highly efficient for H2 production after photodeposition of Pt co-catalyst (Pt@sp2c-COFdpy-Co). The optimized Pt@sp2c-COFdpy-Co exhibited a high photocatalytic H2 production rate of 324.4 μmol/h under visible light irradiation in the presence of 1.0 wt% Pt as co-catalyst, which was higher than Pt@sp2c-COFdpy-Fe and Pt@sp2c-COFdpy-Ni, and it was much higher than that of its counterparts and many reported works. This work provides new insights into design of highly efficient COF-based catalyst for photocatalytic H2 production.

Water process/treatment by a S-scheme Fe2O3/TiO2 heterojunction photocatalyst for excellent antibiotic degradation/CO2 reduction/H2 production; process optimization and mechanistic insights

A facile synthesis approach was employed to fabricate a binary Fe2O3/TiO2 nanocomposite (FeTi4-400) for enhanced photocatalytic hydrogen (H2) production, cephalexin degradation and CO2 reduction under visible light irradiation. Compared to pristine TiO2, FeTi4-400 exhibited improved visible light absorption and promoted charge carrier separation, leading to increased H2 production rate and CO2 conversion into CH4 and CO. This improvement can be attributed to the formation of an S-scheme heterojunction, along with the desirable properties of FeTi4-400, including visible light activity, high surface area, and strong CO2 adsorption. The photocatalyst achieved a maximum H2 production rate of 649 μmol/g·h−1, exceeding that of pure TiO2. Similarly, the highest CO production rate of 16.44 μmol/g·h−1 was attained with FeTi4-400. Furthermore, FeTi4-400 achieved excellent cephalexin degradation (96 %) under optimal conditions, with a degradation rate constant of 0.01 min−1. A plausible cephalexin degradation pathway over FeTi4-400 is proposed. Transient photocurrent measurements and EIS analysis corroborated a significant enhancement in photocatalytic activity for FeTi4-400, attributed to the efficient separation of photogenerated electron-hole pairs. Stability studies demonstrated consistent cephalexin degradation by FeTi4-400 over five consecutive cycles without noticeable photocatalyst deactivation. This work presents a novel strategy for fabricating low-cost, efficient, and readily synthesized nanomaterials for applications in solar energy conversion and environmental remediation.

Design of Z-scheme heterojunction integrated two-compartment plasmonic fabry–perot cavities array with high solar absorptivity for atmospheric pure water splitting

High charge combination and insufficient solar energy utilization are two main problems hindering the efficiency of photocatalytic hydrogen production. In this study, a two-compartment plasmonic moth-eye nanostructured Fabry-Perot (F-P) cavity integrating Z-scheme heterojunctions (TiO2/Au-WO3-Ag/nanohemisphere (NH)/Ag) is proposed to simultaneously reduce the charge recombination and achieve full-spectrum solar light utilization. The overall system comprises a large cavity structured from interconnected upper and under-layer F-P cavities, sharing a consistent nanostructure that facilitates plasmonic F-P enhanced Mie resonance. This design ensures the confinement of ultraviolet, visible, and infrared light within the upper cavity, broadening and intensifying light localization while exhibiting angle-insensitive characteristics. Since the Z-scheme heterojunction is positioned on the top half of the upper F-P cavity, the localized light interacts directly with the Z-scheme heterojunction (TiO2/Au-WO3), significantly boosting hydrogen production efficiency. As evidence, the TiO2/Au-100 nm WO3-Ag/NH/Ag configuration exhibits a solar absorptivity of 71.6 % and achieves H2 production rate of 5.2 mmol·m−2·h−1 for pure water splitting, which is 16.4 times higher than that of TiO2/Au alone under atmospheric condition and without the use of a sacrificial agent. More noteworthy is the fact that no hydrogen peak is detected on the pristine P25 under such conditions.

Oxygen vacancy enriched and Cu single-atom contained covalent organic frameworks: A competitive photocatalyst to promote hydrogen evolution under visible light

Single-atom loaded covalent organic frameworks (COFs) have been rapidly developed in the field of photocatalytic hydrogen production in recent years. Despite the insufficient active sites has been introduced, the high recombination rate of photogenerated carriers has hindered the progress of catalyst development. In this work, a novel approach is proposed to construct oxygen vacancies (OVs) on single atom Cu contained COF-TpPa, acting as an electron collector to facilitate the transfer and utilization of electrons. The Cu-OV-TpPa can provide a remarkable H2 production rate of 2.77 mmol g−1 h−1 under visible light, which is 2.6 times of Cu-P-TpPa (a H2 production rate of 1.02 mmol g−1 h−1). It achieves a high apparent quantum efficiency (AQE) of 20 % at 420 nm with no noble metal cocatalyst. A thorough analysis of carrier lifetime, recombination rate, electric conductivity and charge density reveals that the synergistic effect between OVs and single-atom Cu significantly enhances photogenerated carrier separation efficiency and reduces activation energy. This study presents a new strategy to design COF-based photocatalysts towards a competitive H2 production under visible light.

Ce-modified Cu nanoparticles with N-doped carbon encapsulation for efficient H2 production from aqueous phase reforming of methanol at low temperatures

Aqueous-phase reforming of methanol (APRM) for both hydrogen (H2) production and high pressure storage shows promising potential in mobile/distributed fuel cell stations or vehicles. Currently, achieving efficient H2 production with low CO selectivity (S-CO) at lower temperatures remains a challenge for its application in these fields (rapid start and running in cycles). Herein, the catalyst of Ce-modified Cu nanoparticles with N-doped carbon encapsulation (Cu-CeO2@PVP catalyst) is developed to give excellent H2 production rate at low temperatures ranging from 110 °C to 180 °C, ensuring excellent hydrothermal stability. The H2 production rate of 32.56 μmol·gcat-1·s−1 at 180 °C is 6.1 times to 10.2 times higher than those of commercial catalysts, which demonstrates its superior performance. The combined effect of Cu+/Cu0 and CeO2 promotes the H2 production from CH3OH/H2O. It also suppresses the CO formation by enhancing the H2O dissociation, CO conversion and HCOOH decomposition in APRM. The stable high purified H2 flow from the integrated slurry bed APRM device can start immediately the fuel cell vehicle without any delay.

Boosted photoinduced charge separation in FeNi2S4@Cd0.9Zn0.1S Step-scheme heterojunction for photothermal assisted photocatalytic water splitting into hydrogen

Rational design of photocatalysts with photothermal effect to maximize light utilization is pivotal in achieving superior photocatalytic efficiency. In this work, by coating Cd0.9Zn0.1S (CZS) nanorods on hollow FeNi2S4 (FNS) microspheres with photothermal effect, a novel FeNi2S4@Cd0.9Zn0.1S (FNS@CZS) Step-scheme (S-scheme) heterojunction photocatalyst was constructed for efficient photothermal-assisted hydrogen (H2) evolution via simultaneously employing light and thermal energy. The hollow structure of FNS microsphere not only provides abundant reactive sites but also serves as a supportive substrate for CZS nanorods, effectively inhibiting their agglomeration. And the unique hollow structure of FNS allows for multiple reflections and refractions of visible light, enhancing the local temperature of the photocatalyst. This effectively minimizes thermal losses within the composite system, thereby enhancing the efficiency of light energy utilization. Furthermore, the formation of the S-scheme heterojunction facilitates the efficient separation of photogenerated charge carriers and enhances the activity of redox reactions, thereby boosting the overall photocatalytic activity. Experimental results reveal that the H2 production rate of the FNS@CZS heterojunction reaches 12.9 mmol·g−1·h−1, which is 25.1 times higher than that of pristine CZS. By controlling the experimental temperature, the impact of the photothermal effect on the photocatalytic H2 production rate has been clarified. According to relevant evidence from infrared thermography and DFT calculations, comprehensive analyses and discussions were conducted on the photothermal effect and S-scheme charge transfer mechanisms. This study offers guidance on designing photothermal-enhanced photocatalysts to achieve satisfactory H2 production activity.

Balancing the Charge Separation and Surface Reaction Dynamics in Twin-Interface Photocatalysts for Solar-to-Hydrogen Production.

Solar-driven photocatalytic green hydrogen (H2) evolution reaction presents a promising route toward solar-to-chemical fuel conversion. However, its efficiency has been hindered by the desynchronization of fast photogenerated charge carriers and slow surface reaction kinetics. This work introduces a paradigm shift in photocatalyst design by focusing on the synchronization of charge transport and surface reactions through the use of twin structures as a unique platform. With CdS twin structure (CdS-T) as a model, the role of twin boundaries in modulating surface reactions and facilitating charge migration is systematically investigated. Utilizing transient absorption (TA) and time-resolved infrared (TRIR) spectroscopies, it is revealed that CdS-T achieves charge separation on a picosecond timescale and, importantly, the surface reaction at the twin boundary with the involvement of holes also occurs within 100ps to 3ns. This synchronization of charge donation and surface regeneration significantly enhances the hydrogen evolution process. Accordingly, CdS-T exhibits superior activity for visible light photocatalytic H2 production, withthe H2 production rate of 55.61mmol h-1 g-1 and remarkable stability (>30h), outperforming pristine CdS significantly. This study underscores the transformative potential of twin structures in photocatalysis, offering a new avenue to synchronize charge transport and surface reactions.

Single-atom Barium Promoter Enormously Enhanced Non-noble Metal Catalyst for Ammonia Decomposition.

As a well-established topic, single-atom catalyst has drawn growing interest for its high utilization of metal. However, researchers prefer to develop various active metals with single-atom form, the intrinsic roles of single-atom promoters are usually underrated, which are significant in boosting reaction activity. In this work, Ba single atoms were in situ prepared in the Co-Ba/Y2O3 catalyst with crystallized BaCO3 as the precursor under the ammonia decomposition reaction condition. The optimized Co-Ba/Y2O3 catalyst achieves extremely high H2 production rate of 138.3 mmolH2·gcat-1·min-1 at very low temperature (500 °C, GHSV = 840,000 mL·g-1·h-1) and Co-Ba/Y2O3 exhibits excellent durability during the 350 h test, which realizes the highest activity among all non-noble catalysts, and reaches or even exceeds numerous reported Ru-based catalysts. Both Y2O3 and Co demonstrate positive interactions with Ba, which significantly facilitates the dispersion of Ba species at high temperatures (≥ 600 °C). Ba single atoms significantly enhance the charge density of Co and form additionally active Co-O-Ba-Y2O3 interfacial sites, which alleviates hydrogen poisoning and decreases the reaction barrier of the N-H bond activation of *NH. The exploration of atomically dispersed promoters is groundbreaking in heterogeneous catalysis, which opens up a whole new domain of catalytic material.

Densely populated single‐atom catalysts for boosting hydrogen generation from formic acid

AbstractThe single‐atom M‐N‐C (M typically being Co or Fe) is a prominent material with exceptional reactivity in areas of catalysis for sustainable energy. However, the formation of metal nanoparticles in M‐N‐C materials is coupled with high‐temperature calcination conditions, limiting the density of M‐Nx active sites and thus restricting the catalytic performance of such catalysts. Herein, we describe an effective decoupling strategy to construct high‐density M‐Nx active sites by generating polyfurfuryl alcohol in the MOF precursor, effectively preventing the formation of metal nanoparticles even with up to 6.377% cobalt loading. This catalyst showed a high H2 production rate of 778 mL gCat−1 h−1 when used in the dehydrogenation reaction of formic acid. In addition to the high density of the active site, a curved carbon surface in the structure is also thought to be the reason for the high performance of the catalyst.

Co Cluster-Modified Ni Nanoparticles with Superior Light-Driven Thermocatalytic CO2 Reduction by CH4.

Excessive fossil burning causes energy shortages and contributes to the environmental crisis. Light-driven thermocatalytic CO2 reduction by methane (CRM) provides an effective strategy to conquer these two global challenges. Ni-based catalysts have been developed as candidates for CRM that are comparable to the noble metal catalysts. However, they are prone to deactivation due to the thermodynamically inevitable coking side reactions. Herein, we reported a novel Co-Ni/SiO2 nanocomposite of Co cluster-modified Ni nanoparticles, which greatly enhance the catalytic durability for light-driven thermocatalytic CRM. It exhibits high production rates of H2 (rH2) and CO (rCO, 22.8 and 26.7 mmol min-1 g-1, respectively), and very high light-to-fuel efficiency (ƞ) is achieved (26.8%). Co-Ni/SiO2 shows better catalytic durability than the referenced catalyst of Ni/SiO2. Based on the experimental results of TG-MS, TEM, and HRTEM, we revealed the origin of the significantly enhanced light-driven thermocatalytic activity and durability as well as the novel photoactivation. It was discovered that the focused irradiation markedly reduces the apparent activation energy of CO2 on the Co-Ni/SiO2 nanocomposite, thus significantly enhancing the light-driven thermocatalytic activity.

Thermophilic dark fermentation for hydrogen and volatile fatty acids production from breadcrumbs

Food waste poses significant environmental challenges, with Japan generating 100 million kg of bread waste annually. This study explores the potential of thermophilic dark fermentation to convert bread waste into hydrogen (H2) and volatile fatty acids (VFA). A 3-L continuous stirred-tank reactor (CSTR) was operated for 269 days using breadcrumb as feedstock. The highest H2 production rate of 7.0 L-H2 L−1 d−1 was achieved on day 52 with the production of acetate and butyrate. However, H2 production fluctuated significantly, correlated with the shifts of microbial community structure. Initially, Thermoanaerobacterium saccharolyticum, Thermocoprobibacter melissae, and Anaerocolumna jejuensis coexisted, but An. jejuensis outcompeted others during the deterioration phase, resulting in acetate accumulation without H2 production. Metabolic potential analysis using the phylogenetic investigation of communities by reconstruction of unobserved states 2 (PICRUSt2) revealed that carbohydrate degradation was primarily carried out by An. jejuensis, while protein and lipid degradation involved diverse microbial members. The low functional diversity in carbohydrate degradation was a potential cause of instability. This study demonstrates the feasibility of using bread waste for H2 and VFA production, and provided insights into microbial dynamics essential for stable reactor performance.

Bimetallic NiCo Nanoparticles Embedded in Organic Group Functionalized Mesoporous Silica for Efficient Hydrogen Production from Ammonia Borane Hydrolysis.

In this study, bimetallic NiCo nanoparticles (NPs) were encapsulated within the mesopores of carboxylic acid functionalized mesoporous silica (CMS) through the chemical reduction approach. Both NaBH4 and NH3BH3 were used as reducing agents to reduce the metal ions simultaneously. The resulting composite was used as a catalyst for hydrolysis of ammonia borane (NH3BH3, AB) to produce H2. The bimetallic NiCo NPs supported on carboxylic group functionalized mesoporous silica, referred to as NixCo100-x@CMS, exhibited significantly higher catalytic activity for AB hydrolysis compared to their monometallic counterparts. The remarkable activity of NixCo100-x@CMS could be ascribed to the synergistic contributions of Ni and Co, redox reaction during the hydrolysis, and the fine-tuned electronic structure. The catalytic performance of the NixCo100-x@CMS nanocatalyst was observed to be dependent on the composition of Ni and Co. Among all the compositions investigated, Ni40Co60@CMS demonstrated the highest catalytic activity, with a turn over frequency (TOF) of 18.95 molH2min-1molcatalyst-1 and H2 production rate of 8.0 L min-1g-1. The activity of Ni40Co60@CMS was approximately three times greater than that of Ni@CMS and about two times that of Co@CMS. The superior activity of Ni40Co60@CMS was attributed to its finely-tuned electronic structure, resulting from the electron transfer of Ni to Co. Furthermore, the nanocatalyst exhibited excellent durability, as the carboxylate group in the support provided a strong metal-support interaction, securely anchoring the NPs within the mesopores, preventing both agglomeration and leakage.

Cu/S Co-anchoring junction boosted the photogenerated carrier separation efficiency in g-C3N5 for enhanced H2 evolution

C3N5 is emerging as an important visible light catalyst because of its narrow band gap, nontoxicity and thermal stability. Herein, sulfur-doped g-C3N5 (SCN) was prepared by copolymerization of thioacetamide (TAA) and 3-amino-1,2,4-triazole (3-AT). Then copper nanoparticles (Cu NPs) were anchored onto the SCN framework, resulting in the formation of Cu/SCN. It was found that the average H2 production rate of SCN and Cu/SCN was 0.76 and 1.34 mmol g−1 h−1, which was much higher than that of C3N5, respectively. Acting as a new active spots, sulfur doping effectively reduces the band gap of g-C3N5, and the formation of S-Cu bonds further creates an efficient electron transport pathway. As a result, Cu/SCN possesses a broader visible light absorption spectrum, stronger reduction capability, and greater efficiency in photo-induced carrier separation and transfer. Therefore, this work introduces a novel strategy for design of high efficiency photocatalytic H2 evolution carbon nitride through non-noble metal and sulfur anchoring junction.

Reinforcing Photogenerated Carrier Extraction of Environment-Friendly InP/ZnSeS Quantum Dots for High-Performing Photoelectrochemical Photodetection and Solar Energy Conversion.

Colloidal InP/ZnSeS-based quantum dots (QDs) are considered promising building blocks for light-emitting devices due to their environmental friendliness, high quantum yield (QY), and narrow emission. However, the intrinsic type-I band structure severely hinders potential photoelectrochemical (PEC) applications requiring efficient photoexcited carrier separation and transfer. In this study, the optoelectronic properties of InP/ZnSeS QDs are tailored by introducing Al dopants in the ZnSeS layer, which concurrently passivate the surface defects and act as shallow donor states for suppressed non-radiative recombination and improved charge extraction efficiency. Consequently, as-fabricated InP/ZnSeS:Al QDs-based PEC-type photodetector exhibited a high detectivity up to 1011 Jones and a remarkable responsivity of 0.66 AW-1 at 600nm even under self-powered condition (0V bias). In addition, as-prepared InP/ZnSeS:Al QDs-based photoanode can be alternatively used for PEC hydrogen generation, showing an H2 production rate of 73.7µmol cm-2h-1 under 1 sun illumination (AM 1.5G, 100mW cm-2). The results offer a prospective strategy for optimizing eco-friendly QDs for high-performance multifunctional light detection/conversion devices.

Construction of Au nanoparticles decorated on ZnFe2O4@ZnIn2S4 core-shell structure to enhance photocatalytic hydrogen production

Developing effective photocatalysts for water splitting is essential to generating H2 energy sources. Herein, a novel ZnFe2O4@ZnIn2S4/Au ternary composite (abbreviated as ZFO@ZIS/Au) was successfully designed and fabricated by loading Au nanoparticles on the ZFO@ZIS surfaces for effective photocatalytic H2 generation for the first time. Attributed to the synergistic effect of the traditional II-type heterojunction charge transfer and Au nanoparticles as co-catalysts, the ZFO@ZIS/Au heterojunction generated greater amounts of hydrogen under visible light irradiation. The ZFO-7 %@ZIS/Au-2 catalyst displayed the highest H2 production rate of 1145.38 μmol∙g−1∙h−1, which was almost 3.87 times more than the ZIS value. Furthermore, several characterization techniques were performed to investigate the catalysts and evaluate the catalyst's photocatalytic activity when exposed to visible light. Lastly, a detailed discussion of the corresponding photocatalytic H2 production process of the as-prepared ZFO@ZIS/Au heterojunction was provided. The distinctive research might offer a potential approach for modifying zinc ferrate for photocatalytic hydrogen production.

Construction of 2D/2D Pd Metallene/COFs System with Strong Internal Electric Field for Outstanding Solar Energy Photocatalysis.

Due to the severe recombination of charge carriers, the photocatalytic activity of covalent organic frameworks (COFs) materials is limited. Herein, through simple ultrasound and stirring processes, the Pd metallene (Pde) is successfully combined with 2D COFs to form Pde/TpPa-1-COF (Pde/TPC) composites. Obviously, a strong internal electric field (IEF) is successfully formed in Pde/TPC hybrid materials, which significantly boosts the separation of photogenerated charges. In addition, the matched 2D structure of the two materials can also lead to electronic coupling effects, plentiful active sites, and shortened carrier migration paths. Thus, the Pde/TPC hybrid materials own extraordinary carrier separation ability with a longer carriers lifetime (3.3 ns for Pde/TPC and 2.7 ns for TPC), which can be proved series of photoelectrochemical and spectroscopic tests. Benefiting from the formation of IEF and the matched 2D structure, the 8% Pde/TPC demonstrates the highest photocatalytic H2 evolution efficiency, with H2 production rate reaching up to 5.85 mmolg-1h-1, which is over 25 times greater than that of pristine COFs, also exceeding that of many reported COFs-based photocatalysts. This research provides new perspectives and innovative approaches to further research on enhancing the internal electric field of COFs to promote their photocatalytic performance.

Enhancing photocatalytic performance of covalent organic frameworks via ionic polarization

Covalent organic frameworks have emerged as a thriving family in the realm of photocatalysis recently, yet with concerns about their high exciton dissociation energy and sluggish charge transfer. Herein, a strategy to enhance the built-in electric field of series β-keto-enamine-based covalent organic frameworks by ionic polarization method is proposed. The ionic polarization is achieved through a distinctive post-synthetic quaternization reaction which can endow the covalent organic frameworks with separated charge centers comprising cationic skeleton and iodide counter-anions. The stronger built-in electric field generated between their cationic framework and iodide anions promotes charge transfer and exciton dissociation efficiency. Moreover, the introduced iodide anions not only serve as reaction centers with lowered H* formation energy barrier, but also act as electron extractant suppressing the recombination of electron-hole pairs. Therefore, the photocatalytic performance of the covalent organic frameworks shows notable improvement, among which the CH3I-TpPa-1 can deliver an high H2 production rate up to 9.21 mmol g−1 h−1 without any co-catalysts, representing a 42-fold increase compared to TpPa-1, being comparable to or possibly exceeding the current covalent organic framework photocatalysts with the addition of Pt co-catalysts.

Single‐atom Barium Promoter Enormously Enhanced Non‐noble Metal Catalyst for Ammonia Decomposition

As a well‐established topic, single‐atom catalyst has drawn growing interest for its high utilization of metal. However, researchers prefer to develop various active metals with single‐atom form, the intrinsic roles of single‐atom promoters are usually underrated, which are significant in boosting reaction activity. In this work, Ba single atoms were in situ prepared in the Co‐Ba/Y2O3 catalyst with crystallized BaCO3 as the precursor under the ammonia decomposition reaction condition. The optimized Co‐Ba/Y2O3 catalyst achieves extremely high H2 production rate of 138.3 mmolH2·gcat−1·min−1 at very low temperature (500 °C, GHSV = 840,000 mL·g−1·h−1) and Co‐Ba/Y2O3 exhibits excellent durability during the 350 h test, which realizes the highest activity among all non‐noble catalysts, and reaches or even exceeds numerous reported Ru‐based catalysts. Both Y2O3 and Co demonstrate positive interactions with Ba, which significantly facilitates the dispersion of Ba species at high temperatures (≥ 600 °C). Ba single atoms significantly enhance the charge density of Co and form additionally active Co‐O‐Ba‐Y2O3 interfacial sites, which alleviates hydrogen poisoning and decreases the reaction barrier of the N‐H bond activation of *NH. The exploration of atomically dispersed promoters is groundbreaking in heterogeneous catalysis, which opens up a whole new domain of catalytic material.