Photocatalytic Hydrogen Evolution Performance Research Articles

Surface cyano groups optimize the charge transfer of poly heptazine imide for enhanced photocatalytic H2 evolution

Surface functionalization has been considered as an effective strategy to manipulate charge separation of carbon nitride and therefore to largely improve the photocatalytic H2 evolution efficiency. Poly heptazine imide (PHI) is a new class of crystalline carbon nitride frameworks that exhibits remarkable photocatalytic performance for hydrogen evolution. To further improve the H2 evolution performance of PHI and explore the reaction mechanism, ammonium thiocyanate was used as a precursor for the synthesis of poly heptazine imide at elevated temperatures under molten salt conditions. The optimized PHI with an abundance of surface cyano groups shows a significantly enhanced photocatalytic performance for H2 evolution, which is 4.3 times that on pristine PCN. Most importantly, the surface cyano group adjusts the electron intensity of the polymeric framework, enhances the light absorbance, reduces the bandgap, and improves the charge separation efficiency. The synthetic technique also could be applied to other sulfur-containing precursors for the synthesis of PHI frameworks with excellent hydrogen evolution production performance.

Construction of a Dual-Function Mo-ZIS@Ti for Photocatalytic Benzyl Alcohol Oxidation and Hydrogen Evolution Performance.

The photocatalytic oxidation of benzyl alcohol and the simultaneous evolution of hydrogen from water are efficient dual-optimal routes. It is important to develop composite catalysts that combine redox properties and facilitate electron-hole separation and transport. Herein, the bimetallic-doped Mo-ZIS@Ti photocatalyst was designed and synthesized, and the selective oxidation of benzyl alcohol and hydrogen evolution by water splitting was realized at the same time. Under visible light irradiation, benzyl alcohol was completely converted with more than 99% selectivity for benzaldehyde, and the H2 production rate was 5.6 times higher than the initial ZIS. The exceptional catalytic performance was ascribed to utilizing Ti-MIL-125 as a precursor, wherein slowly releasing-doped Ti formed robust Ti-S bonds that quickly transfer electrons and reduce sites. Meanwhile, doping Mo effectively captures photogenerated holes and acts as active sites for oxidation reactions. Both experimental characterization and work function calculations demonstrate that the bimetallic synergism effectively modulates the electronic structure of ZIS, promotes the directional separation of electrons and holes, and significantly improves the photoactivity and stability of ZIS. This work contributes a route to obtain benzaldehyde and green hydrogen at the same time and also gives new insights for the construction and mechanism study of bimetallic-doping catalysts.

Acid etching-induced nanocutting of LaNiO3 transplanting self-assembled photodiode array-like LaNiO3/N,P-RGO nanoreactor for efficient photocatalytic hydrogen evolution

Nanoscale graphene-semiconductor composite photocatalysts with fascinating properties in the photocatalytic hydrogen evolution have inspired numerous interests in broad research fields. The architectures with efficient light response and promoting charge separation at the interface between reduced graphene oxide (RGO) and semiconductor are critical, yet synthesizing them remains a formidable challenge. Herein, the photodiode array-like LaNiO3/N,P-RGO (LNO/N,P-RGO) nanoreactor was constructed using an innovative strategy of acid etching-induced nanocutting self-assembly. Ammonium dihydrogen phosphate working as both a nitrogen phosphorus co-dopant and an acid etching reagent, cuts perovskite LaNiO3 (LNO) nanoparticles into nanorods, which are bonded evenly on the nitrogen phosphorus co-doped reduced graphene oxide (N,P-RGO) to form an n-n semiconductor heterojunction LNO/N,P-RGO as a photodiode array-like nanoreactor via hydrothermal treatment. The photodiode array-like nanostructure exposes more active sites that are conducive to light absorption. The robust Ni-C and P-O bonds promote the narrowing of space-charge region at the interface by UV irradiation, thereby improving the transport of photogenerated carriers by visible light irradiation. The LNO/N,P-RGO nanoreactor exhibits excellent photocatalytic hydrogen evolution performance with a yield of up to 354 μmol g−1 h−1 under UV–visible light, which is 50 times higher than that of pure perovskite LNO, and it also displays favorable recycling stability.

Retraction Note: Visible light-enhanced photocatalytic dye degradation and hydrogen evolution performance of BiVO4 thin films prepared at various annealing temperatures

Retraction Note: Visible light-enhanced photocatalytic dye degradation and hydrogen evolution performance of BiVO4 thin films prepared at various annealing temperatures

Structurally disordered MoSe2 with rich 1T phase as a universal platform for enhanced photocatalytic hydrogen production

The improvement of surface reactivity in noble-metal-free cocatalysts is crucial for the development of efficient and cost-effective photocatalytic systems. However, the influence of crystallinity on catalytic efficacy has received limited attention. Herein, we report the utilization of structurally disordered MoSe2 with abundant 1T phase as a versatile cocatalyst for photocatalytic hydrogen evolution. Using MoSe2/carbon nitride (CN) hybrids as a case study, it is demonstrated that amorphous MoSe2 significantly enhances the hydrogen evolution rate of CN, achieving up to 11.37 μmol h−1, surpassing both low crystallinity (8.24 μmol h−1) and high crystallinity MoSe2 (3.86 μmol h−1). Experimental analysis indicates that the disordered structure of amorphous MoSe2, characterized by coordination-unsaturated surface sites and a rich 1T phase with abundant active sites at the basal plane, predominantly facilitates the conversion of surface-bound protons to hydrogen. Conversely, the heightened charge transfer capacity of the highly crystalline counterpart plays a minor role in enhancing practical catalytic performance. This approach is applicable for enhancing the photocatalytic hydrogen evolution performance of various semiconducting photocatalysts, including CdS, TiO2, and ZnIn2S4, thereby offering novel insights into the advancement of high-performance non-precious catalysts through phase engineering.

Acceleration of the electron transfer for efficient photocatalytic hydrogen evolution via regulating the surfactant around the active center in 2D MOFs

Although surfactants have been proved to be effective in controlling the size and morphology to prepare high-quality two-dimensional (2D) MOF nanosheets, the impact of surfactants remaining on the 2D MOF nanosheets on their microenvironment is rarely reported. In this paper, polyvinylpyrrolidone (PVP) was used as surfactant to synthesize Co-TCPP(Pd) (abbreviated as Co-Pd) nanosheets, and the content of PVP attached to Co-Pd nanosheets was controlled by ethanol treatment, to regulate the microenvironment around Co-Pd nanosheets. The XRD, FT-IR, XPS, TEM, and TG were used to confirm that after ethanol ultrasonic treatment, the PVP content on Co-Pd nanosheets was gradually reduced without damaging the original structure and morphology of Co-Pd nanosheets. PVP attached to Co-Pd nanosheets will slow down the electron migration rate, affecting the microenvironment around co-catalyst Pd, which has been confirmed by EIS, PL and DFT etc. The results exhibited that the Co-Pd-6 obtained by ethanol ultrasonic treatment 6 times showed the more excellent photocatalytic hydrogen evolution activity (8284.25 umol·g−1·h−1), which was 4.02 times as that of Co-Pd-0 (2059.59 umol·g−1·h−1) without ethanol ultrasonic treatment), indicating that PVP will have a negative impact on the microenvironment around the co-catalyst, thereby affecting the photocatalytic hydrogen evolution performance. This study indicates that efficient photocatalytic hydrogen evolution can be achieved via adjusting the microenvironment around the co-catalyst to promote electron transfer.

Cocreation of photogenerated electron and hole collectors on polymeric carbon nitride synergistically promotes carrier separation and reaction kinetics towards propelling photocatalytic hydrogen evolution

It is a challenging issue for the creation of photogenerated carrier collectors on the photocatalyst to drive charge separation and promote reaction kinetics in the photocatalytic reaction. Herein, based on one-step dual-modulation strategy, IrO2 nanodots are modified at the edge of polymeric carbon nitride (PCN) nanosheets and atomically dispersed Ir atoms are implanted in the skeleton of PCN to obtain a unique Ir-PCN/IrO2 photocatalyst. IrO2 nanodots and atomically dispersed Ir atoms act as hole and electron collectors to synergistically promote the carrier separation and reaction kinetics, respectively, thereby greatly improving the photocatalytic hydrogen evolution (PHE) performance. As a result, without adding additional cocatalyst, the PHE rate over the optimal Ir-PCN/IrO2-2% sample reaches up to 1564.4 μmol h−1 g−1 under the visible light irradiation, with achieving an apparent quantum yield (AQY) of 15.7% at 420 nm.

The WO2.72/CdS0.25Se0.75-DETA nanocomposite with S-scheme heterojunction structures exhibits high efficiency and stable photocatalytic hydrogen evolution performance

Facing the global energy crisis, identifying impactful solutions is imperative. This research introduces the cutting-edge nanocomposites, WO3/CdS0.25Se0.75-Diethylenetriamine (Diethylenetriamine is abbreviated as DETA) with configurations of 20 %, 30 %, and 40 % WO3 (denoted as 20-WO/CSE, WO/CSE, and 40-WO/CSE), highlighted by its innovative S-scheme heterojunction. WO/CSE nanocomposite stands out in the realm of solar energy materials, achieving a superior photocatalytic hydrogen evolution rate of 16.7 mmol g−1h−1. Additionally, it exhibits exceptional corrosion resistance, maintaining performance integrity over four 12-hour testing cycles. The strategic incorporation of WO3 not only enhances the nanocomposite's photocatalytic efficiency but also underscores its potential in surpassing the capabilities of its individual constituents. Through theoretical calculations, the S-scheme heterojunction's effective charge transfer properties are confirmed, positioning this nanocomposite as a significant leap forward in addressing energy challenges through advanced solar energy materials and nanocomposites.

Active sites formed on InVO4/Co3O4 S‐scheme heterostructure for photocatalytic hydrogen production

The reasonable design of S‐scheme heterojunction to avoid unwanted charge transfer paths in hybrid semiconductors is considered to be an attractive method to obtain efficient photocatalytic hydrogen evolution activity. The photocatalytic hydrogen evolution performance of the system was improved by loading ultra‐thin InVO4 nanosheets on the surface of hollow cube Co3O4 to form an S‐scheme heterojunction. Benefiting from the unique nano‐cage structure derived from the zeolitic imidazolate frameworks (ZIF) series, it not only provides a good carrier for activating and stabilizing InVO4 nanosheets but also effectively avoids the masking of active sites caused by self‐agglomeration, which is more conducive to the exposure of more active sites. The optimized InVO4/Co3O4 has a more competitive H2 production, which is undoubtedly due to the construction of S‐scheme heterojunctions and unique spatial structure that facilitates the spatial separation of photoexcited charges. It is further confirmed that the photogenerated carrier transfer follows the S‐scheme mechanism by in‐situ irradiation XPS test.

Carbon vacancies and hydrogen bonds in graphitic carbon nitride: Enhanced charge transfer and photocatalytic hydrogen evolution

Accelerating the separation and transfer of photogenerated electron to the active site is an effective strategy for enhancing the photocatalytic hydrogen evolution. However, it is generally limited by the scarcity of active sites, as well as the sluggish photogenerated electron transfer kinetics. Herein, a g-C3N4 catalyst with controllable carbon vacancy and hydrogen bond was prepared using a hot–cold cycles heat treatment. It is demonstrated that after hot–cold cycles, abundant carbon vacancies were introduced into the catalyst and hydrogen bonds were broken. The abundant carbon vacancies not only provide additional electron-active sites, affords more opportunities for photogenerated electron to transfer to the active site, but also optimize the reaction environment for photogenerated electrons by regulating the hydrogen adsorption kinetics of the photocatalyst. Additionally, the broken hydrogen bonds promotes electron transfer to the active site. The combined action of the two effectively enhances the separation and transfer of photogenerated electron to the optimal active site, ultimately leading to a significant increase in photocatalytic hydrogen evolution. Consequently, the g-C3N4 resulting from the fourth cycles (CN-4) demonstrates a substantial improvement in the performance of photocatalytic hydrogen evolution under visible light irradiation (1.69 mmol·g−1·h−1), which is 4.05 times higher than initial g-C3N4. This work may provide new insights into the defect and hydrogen bond regulation design of g-C3N4.

Efficient photocatalytic hydrogen generation by CeCO3OH/TiO2 composites

Due to its low photogenerated carrier separation efficiency and wide band gap, the photocatalytic activity of TiO2 is not ideal. In this work, CeCO3OH/TiO2 composites were successfully prepared by a simple hydrothermal method. A series of characterisations shows that the CeCO3OH/TiO2 composites improves the photogenerated carrier separation efficiency, narrowes the band gap width and increases the visible light absorption capacity compared with the monomer, enhancing the photocatalytic hydrogen evolution performance. Under visible light irradiation, 20% CeCO3OH/TiO2 exhibites the highest photocatalytic hydrogen production performance of 2386.16 μmol g−1 h−1, which is 18.7 times higher than that of pure TiO2 and 25.8 times higher than that of pure CeCO3OH. It provides ideas for the development of more efficient photocatalytic materials and technologies.

Design of S-scheme Sm-ZnO/N-rGO heterosystem for efficient H2 evolution under visible light illumination

Increasing the separation and transfer of photo-triggered electron-hole pairs is critical for developing a photocatalyst with excellent efficiency for hydrogen evolution reaction. Herein, an efficient and stable S-scheme Sm-ZnO/N-rGO heterosystem is successfully synthesized via a hydrothermal process for increased photocatalytic H2 activity. The anchoring of Sm-doped ZnO nanoparticles onto N-doped rGO nanosheets effectively enhances the light absorption, surface area, and transport and separation of photo-triggered carriers with strong redox potentials owing to the combined impact of doping and heterosystem formation. Upon light illumination, the photocatalytic hydrogen evolution performance over Sm-ZnO/N-rGO reaches 2361.8 μmolh-1g-1, which was significantly higher than that of Sm-ZnO and ZnO/N-rGO catalysts by a factor 5.5 and 2.9, respectively. In addition, the optimized composite shows high stability after five repetitive cycles. This research provides a feasible route to use the synergistic effect of doping and heterojunction for designing outstanding photocatalysts and further verifies the potentiality of ZnO for photocatalysis.

Visible‐Light‐Induced Photocatalytic Hydrogen Evolution Performance of Graphdiyne‐Alkyne Phosphating Mo–Metal‐Organic Frameworks Heterojunction

Herein, the application of graphdiyne (GDY) in photocatalytic splitting of water and hydrogen evolution is explored. In this article, GDY is prepared by ball milling using calcium carbide as raw material, and it is compounded with phosphating Mo–metal‐organic frameworks (MOFs), to explore the photocatalytic hydrogen evolution performance and hydrogen evolution mechanism of composite catalysts. In the results, it is shown that the P–Mo–MOFs (PMF)/G‐25 composite photocatalyst has the best hydrogen evolution activity, and the hydrogen evolution rate is highest at pH = 9, reaching 1668.5 μmol g−1 h−1. Through the four‐cycle hydrogen evolution cycle stability test, the PMF/G‐25 composites still has good hydrogen evolution stability. It is shown that the combination of phosphating Mo–MOFs and GDY can enhance the hydrogen evolution activity and has excellent hydrogen evolution performance. In the Mott–Schottky test, it is found that PMF and GDY are n‐type semiconductors. The conduction and valence values are −0.56 and 1.10 eV for GDY, and −0.68 and 0.97 eV for PMF, respectively. The mechanism of photocatalytic hydrogen evolution is analyzed, and it is speculated that S‐Scheme heterojunction is formed between PMF and GDY to further promote photocatalytic hydrogen evolution.

Artificially regulating the crystallinity for constructing poly(heptazine imide)-based S-scheme homojunction with boosted photocatalytic hydrogen evolution performance

Fabricating homojunction photocatalyst is a promising approach to accelerate the separation and transfer of photogenerated charge carriers, and to boost photocatalytic performance. Herein, a novel poly (heptazine imide) (PHI)-based S-scheme homojunction photocatalyst (U/T-LHPHI) is fabricated through an ionothermal synthesis route, which exhibits particular high and low crystallinity property, intimate interface combination, and locally N self-doping. The regulation of crystallinity contributes to the differentiated electronic structure in PHI, which leads to the establishment of internal electric field (IEF). The intense IEF and N doping level with electron extracting capacity synergistically promote the charge transfer from the high crystalline PHI (HPHI) to the low crystalline PHI (LPHI) following the S-scheme mechanism. Additionally, the strong interfacial interaction improves the interfacial charge transfer dynamics. As a consequence, photogenerated electrons with powerful reducing ability are maintained effectively. Upon light irradiation, the optimized U/T-LHPHI performs an H2 evolution rate of 4880, 2416, and 2375 µmol g−1 h−1 in deionized water, simulated seawater, and real seawater, respectively, which exceed that of many carefully designed noble metal Pt containing photocatalyst. This work provides an important verification that the rational design and construction of homojunction photocatalysts could effectively enhance photocatalytic activity.

Ipolymer Cd3(C3N3S3)2/Zn3(C3N3S3)2 S-scheme heterojunction enhances photocatalytic H2 production

The preparation of S-scheme heterojunctions has attracted considerable attention in the academic community as a highly effective approach to enhance the separation and migration of electrons and holes, thereby significantly improving the catalytic efficiency of photocatalysts. In this work, a novel S-scheme ipolymer heterojunction photocatalyst, Cd3(C3N3S3)2/Zn3(C3N3S3)2 (CdTMT/ZnTMT), which synergy with π-conjugate system, was synthesized using an innovative in-situ hydrothermal method. Through a series of rigorous characterization tests, the formation of an S-scheme heterojunction between CdTMT and ZnTMT was confirmed. Particular emphasis is placed on the effective enhancement of photocatalytic activity of photocatalysts through π-conjugated orbitals and built-in electric field after combining double-organic conjugated polymer-shaped ZnTMT and CdTMT. Performance tests that show the photocatalytic hydrogen evolution performance of the composite was significantly boosted to an impressive 45.24 mmol∙g−1∙h−1, which is 215.43 times that of single catalyst ZnTMT and 1.76 times that of CdTMT. Finally, this paper discusses the possibility and development prospect of double polymer to construct S-scheme heterojunctions to improve the activity of photocatalysts.

Nickel phosphide cocatalyst and carbon defects simultaneously boosting the photocatalytic hydrogen production over carbon nitride

The suppression of photogenerated carrier recombination in carbon nitride and the consequent enhancement of its photocatalytic hydrogen evolution performance have emerged as a research hotspot in the field of photocatalysis. Herein, Nickel phosphide (Ni2P) was anchored onto carbon nitride with carbon defects through a synthesis involving thermal polymerization and photoreduction. The existence of carbon defects derived from the rupture of carbon nitride (CN) heterocycles were beneficial to strengthening optical absorption and the separation capabilities of photogenerated carriers. Furthermore, Ni2P cocatalysts could serve as electron acceptors that effectively accelerate the transfer and transport capabilities of the photogenerated charge carriers. Consequently, the 7 wt% Ni2P/CNN photocatalyst achieved a maximum hydrogen evolution rate of 2062 μmol·g−1·h−1, which was 7.8 times and 6.2 times greater than that of Ni2P/CN and Ni/CNN, respectively, and was comparable to the rate achieved by 3 wt% Pt/CNN. This result was comparable or even better than those reported previously. Our work provided a simply strategy for developing non-precious metal-based nickel phosphide photocatalysts for renewable solar-driven photocatalytic hydrogen production.

Biotemplated silicon carbide-loaded ytterbium oxide: Effective catalyst for photocatalytic hydrogen evolution reactions

SiC-doped Yb2O3 structure (Yb2O3/SiC) was prepared to enhance the photocatalytic hydrogen evolution performance of Yb2O3 nanofiber, which have been performed by using catalyst in the presence of eosin-Y dye and triethanolamine, called photosensitizer and electron donor, respectively under solar light with/out cellulose and chitosan. In this study, cellulose and chitosan were used as biotemplates to increase the hydrogen production of Yb2O3/SiC nanofibrous catalyst in the photocatalytic hydrogen evolution reaction. Bioorganic-inorganic structures, cellulose-Yb2O3/SiC and chitosan-Yb2O3/SiC, were obtained by simply adding cellulose and chitosan to the reaction cell without any additional treatment. Cellulose and chitosan also used as a mediator for dispersion, hydrophilicity, morphological transformation and adhesion to semiconductor with the help of functional groups. The hydrogen production rate of bare SiC, bare Yb2O3, Yb2O3/SiC composite have been measured as 391 μmol g−1, 818 μmol g−1 and 1685 μmol g−1, respectively. Moreover, the hydrogen production rate of cellulose-Yb2O3/SiC and chitosan-Yb2O3/SiC composites were came up to 3346 μmol g−1, 4084 μmol g−1, respectively. These results have been showed that the Yb2O3/SiC nanofibrous catalyst showed higher activity in the presence of cellulose and chitosan. The existence of biopolymers will create a new field in photocatalytic hydrogen production studies with the advantages mentioned above, thanks to the functional groups.

Precise local functionalization of covalent organic framework for efficient carrier separation in photocatalytic H2 evolution

Improving carrier transport rate and suppressing carrier recombination are two huge challenges in the photocatalytic applications of covalent organic frameworks (COFs)-based semiconductors. In this study, we propose a strategy to enhance carrier transport efficiency by regulating the local microenvironment of the electronic characteristics in the acceptors through structural modification. Three different functional group-modified fluorenone-based COFs were successfully synthesized through precise design. The results demonstrate that the photocatalytic hydrogen evolution activities of COFs modified with electron-donating functional groups are significantly higher than that of COFs modified by electron-withdrawing functional groups. Specifically, the photocatalytic hydrogen evolution performance of phenyl-modified FOOPh-COF could reach 228.5 mmol h−1g−1, which is 11.8 times higher than that of Br atom-modified FOOBr-COF (19.3 mmol h−1g−1). Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) results reveal that introducing phenyl groups into the acceptor significantly enhances its inhibitory effect on the carrier recombination. Density functional theory calculations further prove that modifying the acceptor by electron-donating functional groups can achieve the increased electron density in the CO active center. The electrons in the CO region in the phenyl-modified fluorenone structure are more enriched and delocalized, which can enhance the speed of electron migration, shorten the migration distance, and inhibit carrier recombination. After loading Pt, it has the lowest H* adsorption-free energy among three samples. This work clarifies the importance of the functionalization modification of COFs’ acceptors in regulating the local electronic environment and further provides new insights into the structure–activity relationship of fluorenone-based COF-based photocatalysts.

Synergistic effect of donor-acceptor structure and built-in electric field in hollow-spherical carbon nitride homojunction towards effective charge transfer and excellent photocatalytic hydrogen evolution performance

Polymeric carbon nitride (PCN) is regarded as a most promising photocatalyst, but the severe recombination of electron-hole pairs restrains its photocatalytic performance. Herein, a carbon nitride gradient homojunction with donor–acceptor (D-A) structure was successfully synthesized. The D-A structure promoted the electron delocalization, while gradient K intercalation helped establish a strong internal electric field from the interior to the surface. They synergistically inhibited the recombination of electron-hole pairs and led to fast charge transfer and much enhanced photocatalytic hydrogen evolution (PHE) performance. This work developed a novel method to promote the charge carrier transfer in carbon nitrides, which could provide a new perspective for the design and development of carbon nitride-based homojunctions in the application of PHE.

Multiscale understand the tuning photocatalytic hydrogen evolution performances of BiOCl stemmed from engineered crystal facet

BiOCl photocatalyst has been extensively investigated due to unique internal electric field. However, the limited photocatalytic efficiency seriously blocks the further development of this photocatalyst. Here, using one-step hydrothermal process, we prepared the octagonal plate BiOCl, which is characterized with (110) facets. Contrasted with the ordinary BiOCl with (010) and (001) facets, the designed BiOCl-110 exbibits approximately 1.70 times and 3.15 times enhancement in photocatalytic H2 evolution, along with qualified reusability. The experimental findings collectively uncover the origin of high hydrogen production, which (110) facet greatly prolongs the lifetime of carriers, sharply increases the surface photovoltage and reasonably optimizes the carrier transport. Particularly, density functional theory simulations unveil a remarkably reduced transition between valence band maximum and conduction band minimum within BiOCl-110, resulting in a largely increased carrier extraction. Besides, the optimized free energy barriers of intermediates yield proper adsorption and desorption process in overall H2O splitting. Further ab initio molecular dynamics calculations unlock that the distinctive atomic structure on surface of the octagonal plate BiOCl serves as the inherent factor in regulating the element distribution of H2O layer on photocatalyst surface. The facet-dependent electronic structure and facet/H2O interface effects offer crucial understanding for BiOCl in highly effective hydrogen evolution.