Photocatalytic Hydrogen Evolution Rate Research Articles

Synthesis of the composites of carbon quantum dots and metal organic framework and their application in hydrogen evolution

The Ti-MIL-125 metal-organic framework (MOF) functions as a nanoreactor, producing carbon quantum dots (CQDs) within its structure and forming CQD/MOF composites. Similarly, a Pt-CQD/MOF three-component composite is synthesized. Their properties, along with those of CQDs and MOF-free-CQDs (mf-CQDs) enclosed within the MOF, undergo assessment and comparison. Integrating CQDs and Pt minimally alters the MOF structure but reduces specific surface areas due to incorporation. The emitted wavelength of CQD/MOF (570 nm) differs from pristine CQDs (450 nm) and mf-CQDs (496 nm), indicating MOF influence on CQDs' growth and photoluminescence. HOMO and LUMO levels of CQDs/MOF, measured via ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy, are more positive than those of the MOF, suggesting heterogeneous junction formation, aiding electron separation. CQD/MOF exhibits a modest photocatalytic hydrogen evolution rate of 20.4 μmol/g/h. Conversely, Pt-CQD/MOF significantly boosts the rate to 2213 μmol/g/h, underscoring Pt's pivotal catalytic role.

Donor-acceptor covalent organic framework/ZnIn2S4 core-shell structure S-scheme heterostructure for efficient photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) show promising prospect as the photocatalysts with advantages of exceptional light adsorption capability, large specific surface area, and adjustable band structure. However, COFs usually suffer from severe recombination of photogenerated carriers. Therefore, there is an urgent demand to design effective COF-based heterostructures to enhance the separation of carriers. In this work, a porphyrin-based COF with electron donor-acceptor structure is synthesized via condensation polymerization by using 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPPP) and N,N,N',N'-tetra(4-formylphenyl)benzidin (NFPBD) as the donor and acceptor, respectively. Subsequently, ZnIn2S4 (ZIS) are successfully in-situ grown on the surface of porphyrin-based COF, forming a novel core-shell structure. The in-situ synthesized ZIS with positive charges can be easily adsorbed on the negatively charged sites of the COF’s surface via the electrostatic interaction. This organic/inorganic hybrid COF-ZIS heterostructure exhibits a superior photocatalytic hydrogen evolution (PHE) rate of 695 μmol g−1 h−1, approximately three times higher than that of ZIS. The construction of COF-ZIS heterostructure plays an important role in enhancing the separation and transport of photogenerated carriers, which provides more electrons at the surface of ZIS to take part in proton reduction. Electron paramagnetic resonance spectra confirm the charge carriers transfer mode in the COF-ZIS heterostructure via an S-scheme mechanism. Moreover, upon loading Pt as the cocatalyst, the heterostructure achieves an effective PHE rate of 2711 μmol g−1 h−1 along with an exceptional stability. Additionally, the COF-ZIS heterostructure reaches up to 2.45% of apparent quantum efficiency at 400 nm. Notably, the average lifetime of the COF-ZIS heterostructure increases by 43.2% and 98.9% compared to that of ZIS and the COF individually, as observed through single-particle fluorescence spectroscopy. This work gives valuable inspiration into the building of donor-acceptor COF-based S-scheme heterostructures to achieve highly effective green energy conversion by aligning band structures.

Organizing Photosensitive and Photothermal Single-Sites Uniformly in a Trimetallic Metal-Organic Framework for Efficient Photocatalytic Hydrogen Evolution.

Effective combination of the photosensitivity and photothermal propertyin photocatalyst is vital to achievethe maximum light utilization for superior photocatalytic efficiency. Herein, this work successfully organizes photosensitive Cd-NS single-sites and photothermal Ni-NS single-sites uniformly at a molecular level within a tailored trimetallic metal-organic framework. The optimized Ho6-Cd0.76Ni0.24-NS exhibits a superior photocatalytic hydrogen evolution rate of 40.06 mmol g-1 h-1 under visible-light irradiation and an apparent quantum efficiency of 29.37% at 420nm without using cocatalysts or photosensitizers. A systematical mechanism study reveals that the uniformly organized photosensitive and photothermal single-sites have synergistic effect, which form ultrashort pathways for efficient transport of photoinduced electrons, suppress the recombination of photogenerated charge carriers, hence promote the hydrogen evolution activity. This work provides a promising approach for organizing dual-functional single-sites uniformly in photocatalyst for high-performance photocatalytic activity.

Multishelled hollow CaTiO3 cubes decorated with Co0.2Cd0.8S nanoparticles for efficient photocatalytic H2 evolution via S-scheme charge transfer

Rationally designing S-scheme heterostructures with boosted charge separation efficiency and superior redox ability is regarded as an appealing strategy to conquer the shortcomings of mono-component and conventional heterojunction photocatalysts. Herein, a novel hierarchical S-scheme heterostructured photocatalyst was constructed by integrating Co0.2Cd0.8S nanoparticles on multishelled hollow CaTiO3 cubes to substantially improve the photocatalytic hydrogen production activity. An internal electric field (IEF) is formed at the heterojunction interfaces owing to the significant disparity in Fermi level (EF) between Co0.2Cd0.8S and CaTiO3, accompanied by the energy band bending, which enables the S-scheme charge transport route in the Co0.2Cd0.8S/CaTiO3 heterostructure, as verified by electron paramagnetic resonance and theoretical calculations. Benefiting from the boosted separation efficiency and superior redox capability of photocarriers within the constructed S-scheme heterostructure, the optimized Co0.2Cd0.8S/CaTiO3 sample exhibited a significantly improved photocatalytic hydrogen evolution rate of 8.13 mmol h−1 g−1, far exceeding that of mono-component counterparts and previously reported Co0.2Cd0.8S- or CaTiO3-based photocatalysts. This study is anticipated to inspire the strategic development of other economical and efficient S-scheme photocatalytic systems with enhanced H2 evolution activity.

Topological insulator Bi2Te3 and graphene oxide synergistically enhance the photothermal effect and photocatalytic hydrogen evolution activity

Photothermal co-catalysis with the partial conversion of solar energy to thermal energy has the potential to overcome the current bottleneck of realizing efficient photocatalytic hydrogen production with zero artificial energy consumption. However, it is still challenging to design highly efficient photocatalysts that can make use of light and thermal energy synergistically. In this work, we successfully improved the photothermal effect and visible-light-catalyzed hydrogen evolution performance by constructing a novel heterojunction based on the topological insulator Bi2Te3 and graphene oxide (GO) synergistically modified with Zn0.67Cd0.33S. The photocatalytic hydrogen evolution rate of the 1.1 wt% Bi2Te3@0.05% GO@Zn0.67Cd0.33S heterojunctions reached 11.52 mmol/h/g (Apparent Quantum Yield of 21.7%), which was 12.9 times higher than that of pure Zn0.67Cd0.33S. Furthermore, the hydrogen production rate reached 71.79 mmol/h/g without cooling. The improved photocatalytic activity originated from the synergistic enhancement of visible-light absorption and the systematic enhancement of the photothermal effect by the Bi2Te3 and GO. In addition, the high electrical conductivity of Bi2Te3 and the high proton conductivity of GO not only increased the electron transfer rate but also synergistically mediated the acceleration of the hydrogen generation reaction. A strong built-in electric field is formed between Bi2Te3 and Zn0.67Cd0.33S, which greatly facilitates the efficient separation of photogenerated carriers. The obtained results illustrate a promising strategy for the development of efficient new photothermal catalysts.

Double S-scheme Cu2−xSe/twinned-Cd0.5Zn0.5S homo-heterojunctions with surface plasmon effects for efficient photocatalytic H2 evolution

The enhancement of charge separation and utilization efficiency in both the bulk phase and interface of semiconductor photocatalysts, as well as the expansion of light absorption range, are crucial research topics in the field of photocatalysis. To address this issue, twinned Cd0.5Zn0.5S (T-CZS) homojunctions consisting of wurtzite Cd0.5Zn0.5S (WZ-CZS) and zinc blende Cd0.5Zn0.5S (ZB-CZS) were synthesized via a hydrothermal method to facilitate the bulk-phase charge separation. Meanwhile, Cu2−xSe with localized surface plasmon resonance effect (LSPR) generated by Cu vacancies was also obtained through a hydrothermal process. Due to their opposite electronegativity, a solvent evaporation strategy was employed to combine Cu2−xSe and T-CZS by intermolecular electrostatic. After optimization, the photocatalytic hydrogen (H2) evolution rate of 5 wt% Cu2−xSe/T-CZS reached an impressive value of 60 mmol∙h−1∙g−1, which was 4.6 and 66.6 times higher than that of pure Cu2−xSe and T-CZS, respectively. Furthermore, this composites demonstrated a remarkable rate of 0.46 mmol∙h−1∙g−1 under near-infrared (NIR) wavelength (>800 nm). The enhanced performance observed in Cu2−xSe/T-CZS can be attributed to its unique and efficient double S-scheme charge transfer mechanism which effectively suppresses rapid recombination of electron-hole pairs both within the bulk phase and at the surface interfaces; this conclusion is supported by Density Functional Theory (DFT) calculations as well as electron paramagnetic resonance spectroscopy analysis. Moreover, incorporation of Cu2−xSe enables effective utilization ultraviolet visible-near infrared (UV–Vis-NIR) light by the composites while facilitating injection “hot electrons” into T-CZS for promoting photocatalytic reactions. This study provides a potential strategy for achieving efficient solar energy conversion through synergistic integration of non-stoichiometric plasmonic materials with photocatalysts with twinned-twinned structures.

Energy transfer enhanced photocatalytic hydrogen evolution in organic heterostructure nanoparticles via flash nanoprecipitation processing

Organic nanophotocatalysts are promising candidates for solar fuels production, but they still face the challenge of unfavorable geminate recombination due to the limited exciton diffusion lengths. Here, we introduce a binary nanophotocatalyst fabricated by blending two polymers, PS-PEG5 (PS) and PBT-PEG5 (PBT), with matched absorption and emission spectra, enabling a Förster resonance energy transfer (FRET) process for enhanced photocatalysis. These heterostructure nanophotocatalysts are processed using a facile and scalable flash nanoprecipitation (FNP) technique with precious kinetic control over binary nanoparticle formation. The resulting nanoparticles exhibit an exceptional photocatalytic hydrogen evolution rate up to 65 mmol g−1 h−1, 2.5 times higher than that single component nanoparticle. Characterizations through fluorescence spectra and transient absorption spectra confirm the hetero-energy transfer within the binary nanoparticles, which prolongs the excited-state lifetime and extends the namely “effective exciton diffusion length”. Our finding opens new avenues for designing efficient organic photocatalysts by improving exciton migration.

Molecular engineering in tunable crystallinity of 2D covalent organic frameworks for efficient photocatalytic hydrogen evolution

The strategy of molecular engineering has been employed to build the structure–property–activity relationship for covalent organic frameworks (COFs) with efficient photocatalytic water splitting for hydrogen production. However, previous reports focus on the impact of molecular design on COFs’ physicochemical properties, the crystallinity differences are usually ignored and related studies remain rare. Herein, we describe the preparation of a series of structurally related COFs with similar chemical compositions but have different numbers of nitrogen (N) atoms in the central aromatic ring via an efficient crystallization strategy using of 2,4,6-triformyl resorcinol (TFR). On one hand, the introduction of N atoms reduces π-π stacking interaction during the formation of framework, leading to a decrease in crystallinity. On the other hand, it contributes to enhancing the photocatalytic performance of the materials by varying the electronic structures. Consequently, our results revealed that the photocatalytic hydrogen evolution (PHE) rate is 61.22 mmol g−1 h−1 for COF-905-1N, significantly higher than COF-905-3N (40.60 mmol g−1 h−1) and COF-905 (26.23 mmol g−1 h−1). This study not only provide fundamental insights into formation mechanism of COFs, but also provide a practical approach to enhance COF-based photocatalytic performance.

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.

Construction of Ni2P modified N-doped TiO2 flower-like microspheres with rich 0D/2D heterojunctions for enhanced hydrogen evolution reaction

Ni2P nanocrystals modified N-doped TiO2 flower-like microspheres (Ni2P/N-TFMs) with rich 0D/2D heterojunctions were successfully synthesized via a facile hydrothermal-calcination route. The results indicate that N-TFMs are assembled by interlaced nanosheets with the thickness of only 3–8 nm, which provide abundant anchoring sites for the loading of Ni2P. Notably, the doping of N dopant effectively broadens the spectral response range of TFMs due to the formation of N 2p impurity energy level, and the formed 0D/2D heterojunctions between Ni2P nanocrystals and nanosheet units greatly facilitate the separation of photogenerated carriers and improve the photocatalytic reaction kinetic. Owing to the advantages in energy band structure and surface morphology, the synthesized 10Ni2P/N-TFMs composite exhibits a remarkably enhanced photocatalytic hydrogen evolution rate (0.368 mmol h−1 g−1) compared with commercial P25 TiO2 and N-TFMs under visible light irradiation, implying a wide application prospect of this kind of nanostructure in the field of green hydrogen production.

Interface-induced charge transfer pathway switching of a Cu2O-TiO2 photocatalyst from p-n to S-scheme heterojunction for effective photocatalytic H2 evolution

Photocatalytic hydrogen evolution from water splitting is an appealing method for producing clean chemical fuels. Cu2O, with a suitable bandgap, holds promise as a semiconductor for this process. However, the strong photo-corrosion and rapid charge recombination of Cu2O strongly limit its application in the photocatalytic fields. Herein, an S-scheme heterojunction photocatalyst composed of TiO2 and Cu2O was rationally designed to effectively avoid the photo-corrosion of Cu2O. The introduction of an interfacial nitrogen-doped carbon (NC) layer switches the heterojunction interfacial charge transfer pathway from the p-n to S-scheme heterojunction, which avoids excessive accumulation of photogenerated holes on the surface of Cu2O. Meanwhile, the hybrid structure shows a broad spectral response (300–800 nm) and efficient charge separation and transfer efficiency. Interestingly, the highest photocatalytic hydrogen evolution rate of TiO2-NC-3%Cu2O-3%Ni is 13521.9 μmol g−1 h−1, which is approximately 664.1 times higher than that of pure Cu2O. In-situ X-ray photoelectron spectroscopy and Kelvin probe confirm the charge transfer mechanism of S-scheme heterojunction. The formation of S-scheme heterojunctions effectively accelerates the separation of photogenerated electron-hole pairs and enhances redox capacity, thereby improving the photocatalytic performance and stability of Cu2O. This study provides valuable insights into the rational design of highly efficient Cu2O-based heterojunction photocatalysts for hydrogen production.

Functionalized Linear Conjugated Polymer/TiO2 Heterojunctions for Significantly Enhancing Photocatalytic H2 Evolution.

Conjugated polymers (CPs) have attracted much attention in recent years due to their structural abundance and tunable energy bands. Compared with CP-based materials, the inorganic semiconductor TiO2 has the advantages of low cost, non-toxicity and high photocatalytic hydrogen production (PHP) performance. However, studies on polymeric-inorganic heterojunctions, composed of D-A type CPs and TiO2, for boosting the PHP efficiency are still rare. Herein, an elucidation that the photocatalytic hydrogen evolution activity can actually be improved by forming polymeric-inorganic heterojunctions TFl@TiO2, TS@TiO2 and TSO2@TiO2, facilely synthesized through efficient in situ direct C-H arylation polymerization, is given. The compatible energy levels between virgin TiO2 and polymeric semiconductors enable the resulting functionalized CP@TiO2 heterojunctions to exhibit a considerable photocatalytic hydrogen evolution rate (HER). Especially, the HER of TSO2@TiO2 heterojunction reaches up to 11,220 μmol g-1 h-1, approximately 5.47 and 1260 times higher than that of pristine TSO2 and TiO2 photocatalysts. The intrinsic merits of a donor-acceptor conjugated polymer and the interfacial interaction between CP and TiO2 account for the excellent PHP activity, facilitating the separation of photo-generated excitons. Considering the outstanding PHP behavior, our work discloses that the coupling of inorganic semiconductors and suitable D-A conjugated CPs would play significant roles in the photocatalysis community.

Hydrogen-bonded organic framework derived ultra-fine ZnCdS/ZnS heterojunction with high-porosity for efficient photocatalytic hydrogen production

The introduction of metal complex units makes it possible to expand the functional applications of metal hydrogen-bonded organic frameworks (M-HOFs). An M-HOFs-templated strategy was developed to construct ultra-fine ZnCdS/ZnS heterojunction with high-porosity for efficient photocatalytic hydrogen production. Due to the weak and feasible hydrogen-bonding interactions, the nonmetallic units on HOFs can be quickly replaced by S2− in aqueous solution and derived into porous sulfides without pyrolysis process. Surprisingly, the surface area of ZnCdS/ZnS heterojunction was up to 320 m2 g−1. The ultra-fine heterojunction with high porosity offered more surface reaction sites and shortened carrier transport distance, improving separation efficiency of photogenerated electrons and holes. The size and structure-dependent properties of ZnCdS/ZnS heterojunction exhibited excellent photocatalytic hydrogen evolution rate, which was 1.68 mmol h−1 without cocatalyst. This study provides a novel strategy for constructing ultra-fine heterojunction with high porosity and high surface area to achieve efficient H2 evolution.

Novel hollow core-shell Zn0.5Cd0.5S@ZnIn2S4/MoS2 nanocages with Z-scheme heterojunction for enhanced photocatalysis of hydrogen generation

The development of low-cost and efficient metal sulfide photocatalysts through morphological and structural design is vital to the advancement of the hydrogen economy. However, metal sulfide semiconductor photocatalysts still suffer from low carrier separation and poor solar-to-hydrogen conversion efficiencies. Herein, two-dimensional ZnIn2S4 nanosheets were grown on Zn0.5Cd0.5S hollow nanocages to construct Zn0.5Cd0.5S@ZnIn2S4 hollow nanocages for the first time. Novel hollow core–shell Zn0.5Cd0.5S@ZnIn2S4/MoS2 nanocages with Z-scheme heterojunction structures were obtained by incorporating MoS2 nanosheet co-catalyst via the solvothermal method. The resulting Zn0.5Cd0.5S@ZnIn2S4/MoS2 exhibited unique structural and compositional advantages, leading to remarkable photocatalytic hydrogen evolution rates of up to 8.5 mmol·h−1·g−1 without the use of any precious metal co-catalysts. This rate was 10.6-fold and 7.1-fold higher compared to pure ZnIn2S4 and Zn0.5Cd0.5S, respectively. Moreover, the optimized Zn0.5Cd0.5S@ZnIn2S4/MoS2 photocatalyst outperformed numerous reported ZnIn2S4-based photocatalysts and some ZnIn2S4-based photocatalysts based on precious metal co-catalysts. The exceptional photocatalytic performance of Zn0.5Cd0.5S@ZnIn2S4/MoS2 can be attributed to the Z-scheme heterojunction of core–shell structure that enhanced charge carrier separation and transport, as well as the co-catalytic action of MoS2. Overall, the proposed Zn0.5Cd0.5S@ZnIn2S4/MoS2 with heterojunction structure is a promising candidate for the preparation of efficient photocatalysts for solar-to-hydrogen energy conversion.

Crystal Facet Engineering on SrTiO3 Enhances Photocatalytic Overall Water Splitting.

Single-crystal semiconductor-based photocatalysts exposing unique crystallographic facets show promising applications in energy and environmental technologies; however, crystal facet engineering through solid-state synthesis for photocatalytic overall water splitting is still challenging. Herein, we develop a novel crystal facet engineering strategy through solid-state recrystallization to synthesize uniform SrTiO3 single crystals exposing tailored {111} facets. The presynthesized low-crystalline SrTiO3 precursors enable the formation of well-defined single crystals through kinetically improved crystal structure transformation during solid-state recrystallization process. By employing subtle Al3+ ions as surface morphology modulators, the crystal surface orientation can be precisely tuned to a controlled percentage of {111} facets. The photocatalytic overall water splitting activity increases with the exposure percentage of {111} facets. Owing to the outstanding crystallinity and favorable anisotropic surface structure, the SrTiO3 single crystals with 36.6% of {111} facets lead to a 3-fold enhancement of photocatalytic hydrogen evolution rates up to 1.55 mmol·h-1 in a stoichiometric ratio of 2:1 than thermodynamically stable SrTiO3 enclosed with isotropic {100} facets.

A green and environmentally benign route to synthesizing Z-scheme Bi2S3-TCN photocatalyst for efficient hydrogen production.

Designing and developing photocatalysts with excellent performance in order to achieve efficient hydrogen production is an important strategy for addressing future energy and environmental challenges. Traditional single-phase photocatalytic materials either have a large bandgap and low visible light response or experience rapid recombination of the photogenerated carriers with low quantum efficiency, seriously hindering their photocatalytic applications. To solve these issues, an important solution is to construct well-matched heterojunctions with highly efficient charge separation capabilities. To this end, an in situ sulfurization reaction was adopted after the deposition of Bi3+ supramolecular complex on a layered supramolecular precursor of tubular carbon nitride (TCN). X-ray diffraction (XRD) patterns confirmed that the as-prepared sample has a good crystalline structure without any other impurities, while high-resolution transmission electron microscopy (HR-TEM) revealed that the heterojunction possesses a 2D structure with a layer of nano-array on its surface. Combined Fourier-transform infrared (FT-IR) spectra and energy-dispersive X-ray spectroscopy (EDX) revealed the interfacial interactions. Owing to the formation of the Z-scheme heterojunction, the visible light adsorption and the separation efficiency of the photo-generated carriers are both obviously enhanced, leaving the high energy electrons and high oxidative holes to participate in the photocatalytic reactions. As a result, the photocatalytic hydrogen evolution rate of Bi2S3-TCN achieves 65.2μmolg-1·h-1. This proposed green and environmentally benign route can also be applied to construct other sulfides with 2D TCN, providing some important information for the design and optimization of novel carbon-nitride-based semiconductors.

Enhanced protonation ability of covalent organic frameworks via N,O-bidentate chelation for photocatalytic H2 evolution.

Inspired by the bidentate coordination chemistry of metal ions, we incorporated hydroxyl (OH) and methoxy (OMe) groups into the skeleton of imine-linked COFs to improve their protonation ability via intramolecular hydrogen bonds (O-H⋯NC). In comparison with the pristine COFs possessing monodentate nitrogen coordination sites, OH and OMe functionalized COFs with (N,O)-bidentate chelating sites exhibited up to 13.8 times faster photocatalytic hydrogen evolution rates (HERs).

Self-assembly of Pt(ii)-tetrakis(pentafluorophenyl)porphyrin via F⋯F interaction for efficient cocatalyst-free photocatalytic hydrogen evolution

Self-assembled PtPFTPP via dominant F⋯F interaction restricts aggregation caused quenching (ACQ) in the solid state. This leads to longer-lived photoexcited triplet and thereby higher photocatalytic hydrogen evolution rate of 400 μmol g−1 h−1 compared to self-assembled PtTPP with noticeable ACQ.

Enhancement of covalent triazine frameworks containing S heteroatom for photocatalytic hydrogen evolution: the role of composite PEG

The higher the content of PEG filled in the pores of TTBT-COF, the higher the hydrogen evolution rate. The photocatalytic hydrogen evolution rate of TTBT-COF@PEG30 is 1.51 times that of pristine TTBT-COF.

Isotype heterojunction: tuning the heptazine/triazine phase of crystalline nitrogen-rich C3N5 towards multifunctional photocatalytic applications.

Photocatalytic technology has been well studied as a means to achieve sustainable energy generation through water splitting or chemical synthesis. Recently, a low C/N atomic ratio carbon nitride allotrope, C3N5, has been found to be highly prospective due to its excellent electronic properties and ample N-active sites compared to g-C3N4. Tangentially, crystalline g-C3N4 has also been a prospective candidate due to its improved electron transport and extended π-conjugated system. For the first time, our group successfully employed a one-step molten salt calcination method to prepare novel N-rich crystalline C3N5 and elucidate the effect of calcination temperature on the heptazine/triazine phase. Calcination temperatures of 500 °C (CC3N5-500) and 550 °C (CC3N5-550) lead to crystalline carbon nitride with both heptazine and triazine phases, forming an intimate isotype heterojunction for robust interfacial charge separation. An excellent photocatalytic hydrogen evolution rate (359.97 μmol h-1; apparent quantum efficiency (AQE): 12.86% at 420 nm) was achieved using CC3N5-500, which was 15-fold higher than that of pristine C3N5. Furthermore, CC3N5-500 exhibited improved activity for simultaneous benzyl alcohol oxidation and hydrogen production, as well as H2O2 production (AQE: 9.49% at 420 nm), signifying its multitudinous photoredox capabilities. Moreover, the recyclability tests of the optimal CC3N5-500 on a 3D-printed substrate also showed a 92% performance retention after 4 cycles (16 h). This highlights that crystalline C3N5 significantly augmented the reaction performance for diverse multifunctional solar-driven applications. As such, these results serve as a guide toward the structural tuning of 2D metal-free carbon nanomaterials with tunable crystallinity toward achieving boosted photocatalysis.