Outstanding Oxygen Evolution Research Articles

Lattice modulation strategy toward efficient and durable RuO2‐based catalysts for acidic water oxidation

AbstractRutile RuO2 is recognized for its outstanding acidic oxygen evolution reaction (OER) activity and notable cost advantage compared to iridium oxide for proton exchange membrane water electrolyzers (PEMWEs). However, the unsatisfactory stability of RuO2 hinders its practical application. Here, we report a lattice modulation strategy to enhance both the OER activity and stability of RuO2. Interestingly, the newly synthesized Mo0.15Nb0.05‐RuO2, with Mo doped first and then Nb, presents the greatest lattice spacing and possesses an overpotential of merely 205 mV at 10 mA cm−2, which significantly outperforms Nb0.05Mo0.15‐RuO2 (239 mV), where Nb was doped first followed by Mo, as well as the initial RuO2 (323 mV). Remarkably, Mo0.15Nb0.05‐RuO2 requires only 1.76 V to achieve 1 A cm−2 and exhibits exceptional stability in PEMWE testing, with a voltage rise of only 58 mV at 200 mA cm−2 for more than 80 h.

N, S, P co-doped Co/Co3O4/C particles on carbon fiber paper as a self-supported bifunctional catalyst for direct seawater splitting

To optimize the distribution and transportation of electrical energy, converting surplus or low-quality electricity through electrocatalytic seawater splitting to produce hydrogen is an ideal method. In this work, we developed a bifunctional electrocatalyst (ZIF-9/CP-S-P) through the in-situ growth of ZIF-9 on the carbon fiber paper (CP), followed by sequential sulfurization and phosphidation. This catalyst achieves stable hydrogen and oxygen production in natural seawater, displaying outstanding oxygen evolution activity with an overpotential of just 390mV at 10mA/cm² (Tafel slope: 426.5mV/dec) and impressive hydrogen evolution activity with an overpotential of only 578mV at 10mA/cm² (Tafel slope: 287.7mV/dec). The two-electrode electrolyzer assembled by ZIF-9/CP-S-P || ZIF-9/CP-S-P was conducted the chronoamperometry test for 20000s in 1M phosphate buffer solution and for 100000s in natural seawater, and its performance was comparable to that of commercial Pt/C || IrO2. These findings indicate the potential of ZIF-9/CP-S-P catalyst for practical applications in direct seawater splitting to produce hydrogen and oxygen.

Interface-Strengthened Ru-Based Electrocatalyst for High-Efficiency Proton Exchange Membrane Water Electrolysis at Industrial-Level Current Density

Developing an OER electrocatalyst that balances high performance with low cost is crucial for widely adopting PEM water electrolyzers. Ru-based catalysts are gaining attention for their cost-effectiveness and high activity, positioning them as promising alternatives to Ir-based catalysts. However, Ru-based catalysts can be prone to oxidation at high potentials, compromising their durability. In this study, we utilize a simple synthesis method to synthesize a SnO2, Nb2O5, and RuO2 composite catalyst (SnO2/Nb2O5@RuO2) with multiple interfaces and abundant oxygen vacancies. The large surface area and numerous active sites of the SnO2/Nb2O5@RuO2 catalyst lead to outstanding acidic oxygen evolution reaction (OER) performance, achieving current densities of 10, 50, and 200 mA cm−2 at ultralow overpotentials of 287, 359, and 534 mV, respectively, significantly surpassing commercial IrO2. Moreover, incorporating Nb2O5 into the SnO2/Nb2O5@RuO2 alters the electronic structure at the interfaces and generates a high density of oxygen vacancies, markedly enhancing durability. Consequently, the membrane electrode composed of SnO2/Nb2O5@RuO2 and commercial Pt/C demonstrated stable operation in the PEM cell for 25 days at an industrial current density of 1 A cm−2. This research presents a convenient approach for developing a highly efficient and durable Ru-based electrocatalyst, underscoring its potential for proton exchange membrane water electrolysis.

The Construction of Face-to-Face Combination between NiFe-layered Double Hydroxide Nanosheets and Monolayer rGO for Efficient Water Splitting and Oxygen Reduction.

Developing cost-effective and efficient electrocatalysts is essential for advancing a green energy future. Herein, a NiFe-layered double hydroxide loaded on reduced graphene oxide (NiFe-LDHs@rGO) hybrid was synthesized using a straightforward three-step process involving exfoliation tearing, electrostatic self-assembly, and chemical reduction. The face-to-face packing and ultrathin exfoliation enable strong heterogeneous interactions, fully harnessing the potential of these complementary two-dimensional counterparts. Consequently, the resultant catalyst displays outstanding oxygen evolution reaction (OER) catalytic activity and stability, whose overpotential is as low as 241 mV at 30 mA cm-2 and 255 mV at 50 mA cm-2 with a low Tafel slope of 62.1 mV dec-1. Both the experimental results and density functional theory (DFT) calculations reveal that the face-to-face assembly strengthens the electronic interactions between NiFe-LDHs and rGO, which effectively modulates the d-band center of Ni and Fesites and improves the reaction kinetics for OER. Moreover, the resultant NiFe-LDHs@rGO hybrids exhibit excellent multifunctional catalytic performance. Its hydrogen evolution reaction (HER) activity is endowed by Fe-site of NiFe-LDHs and defect states rGO and achieves a low voltage of 1.68 V to drive a current density of 10 mA cm-2 for overall water splitting. The face-to-face heteroassembly also imparts NiFe-LDHs@rGO with superior oxygen reduction reaction (ORR) activity, with a half-wave potential of 0.70 V and a limiting current density of 4.2 mA cm-2. Its ORR primarily follows a four-electron transfer pathway with a minor contribution from a two-electron process. This study establishes the groundwork for optimizing two-dimensional heterogeneous interfaces in LDH@carbon-based materials for advanced energy conversion.

NixB/Mo0.8B3 Nanorods Encapsulated by a Boron‐Rich Amorphous Layer for Universal pH Water Splitting at the Ampere Level

AbstractHeterostructured interfaces are crucial to electrocatalysts for water splitting. Herein, coral‐like multiheterostructured NixB/Mo0.8B3 (NMB) nanorods encapsulated by a boron‐rich amorphous layer are prepared for water splitting. Density‐functional theory (DFT) calculations indicate that the NMB interface adjusts the d‐band center and electronic structure of the molybdenum sites. Owing to the strong electronic coupling between Ni, Mo, and B at the heterojunction, large number of exposed catalytic active sites, as well as the special hydrophilic characteristics endowed by the surrounding amorphous layer, the NMB catalyst exhibits remarkable universal‐pH hydrogen evolution reaction (HER) activity with low overpotentials (η) of 15, 26, and 83 mV to deliver 10 mA cm−2 in basic, acid, and neutral media, respectively, and outstanding oxygen evolution reaction (OER) characteristics in the basic medium with η10 and η500 of 170 and 420 mV, respectively. The unique self‐supporting 3D hierarchical interconnected structure facilitates mass transport thus leading to high mechanical stability for 450 and 200 h in HER and OER at ≈1000 mA cm−2. More importantly, the NMB exhibits excellent performance toward overall‐water electrolysis as a bifunctional catalyst with ultralow cell voltages of 1.45/1.56/1.85 V @ 10/100/1000 mA cm−2, demonstrating the large potential in industrial water splitting applications.

In Situ Reconstructing NiFe Oxalate Toward Overall Water Splitting.

Surface reconstruction plays an essential role in electrochemical catalysis. The structures, compositions, and functionalities of the real catalytic species and sites generated by reconstruction, however, are yet to be clearly understood, for the metastable or transit state of most reconstructed structures. Herein, a series of NiFe oxalates (NixFe1- xC2O4, x = 1, 0.9, 0.7, 0.6, 0.5, and 0) are synthesized for overall water splitting electrocatalysis. Whilst NixFe1-xC2O4 shows great hydrogen evolution reaction (HER) activity, the in situ reconstructed NixFe1-xOOH exhibits outstanding oxygen evolution reaction (OER) activity. As identified by the in situ Raman spectroscopy and quasi-in situ X-ray absorption spectroscopy (XAS) techniques, reconstructions from NixFe1-xC2O4 into defective NixFe1-xOOH and finally amorphous NixFe1-xOOH active species (R-NixFe1-xOOH) are confirmed upon cyclic voltammetry processes. Specifically, the fully reconstructed R-Ni0.6Fe0.4OOH demonstrates the best OER activity (179mV to reach 10mA cm-2), originating from its abundant real active sites and optimal d-band center. Benefiting from the reconstruction, an alkaline electrolyzer composed of a Ni0.6Fe0.4C2O4 cathode and an in situ reconstructed R-Ni0.6Fe0.4OOH anode achieves a superb overall water splitting performance (1.52 V@10mA cm-2). This work provides an in-depth structure-property relationship understanding on the reconstruction of catalysts and offers a new pathway to designing novel catalyst.

Carbon cloth-based meteorite-like Co–CuS/MoS2 heterostructure for efficient water electrolysis

Developing low-cost, high-efficiency electrocatalysts is critically important for efficient hydrogen production. In this study, a novel electrocatalyst, Co–CuS/MoS2 nanocomposite, was successfully synthesized via ion exchange on carbon cloth using Evans-Showell type polyoxometalate (NH4)6 [Co2Mo10O38H4]·11H2O (Co2Mo10) as a precursor and thiourea in a hydrothermal reaction. The optimized Co–CuS/MoS2 exhibited outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities, with overpotentials of 90 mV and 270 mV at a current density of 10 mA cm−2, respectively, and demonstrated long-term stability in alkaline electrolytes. The superior performance of this catalyst is attributed to the high charge transfer rates between MoS2 and CuS, abundant heterostructure interfaces, and efficient diffusion channels. This study provides a new design strategy for exploring efficient bifunctional electrocatalysts.

Deliberate Amorphization of Co-MOF for Constructing Crystalline-Amorphous Heterostructures Toward High-Performance Water Electrolysis.

The endowment of metal organic frameworks (MOF) with superior electrocatalytic performance without compromising their structural/compositional superiorities is of great significance for the development of renewable energy devices, yet remains a grand challenge. Herein, a deliberate partial amorphization strategy is developed to construct a heterostructured electrocatalyst consisting of crystalline Co-MOF and amorphous Co-S nanoflake arrays aligned on the carbon cloth (CC) substrate (abbreviated as Co-MOF/Co-S@CC hereafter) through a rapid sulfuration method. The simultaneous implement of crystalline-amorphous (c-a) heterostructure and nanoflake arrayed architecture on CC substrate renders the Co-MOF/Co-S@CC with abundant and tight active sites, accelerated charge transfer rate, regulated electronic structures, and reinforced structural stability. As such, the obtained Co-MOF/Co-S@CC electrode demonstrates outstanding electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances with the overpotentials of 64 and 217mV at 10mA cm-2, respectively. Moreover, a two-electrode electrolyzer assembled by Co-MOF/Co-S@CC electrodes exhibits the lower cell voltages and larger current densities than those of Pt/C and RuO2 counterparts, excellent reversibility and prominent long-term stability, representing a great prospect for feasible H2 production. This adopted concept of c-a heterostructure for electronic regulation may bring about insightful inspiration for designing high-performance electrocatalysts for sustainable energy systems.

Unveiling the Role of Electrocatalysts Activation for Iron‐Doped Ni Oxyhydroxide in Enhancing the Catalytic Performance of Oxygen Evolution Reaction

Water electrolysis using renewable electricity is a promising strategy for high‐purity hydrogen production. To realize the practical application of water electrolysis, an electrocatalyst with high redox properties and low cost is essential for enhancing the sluggish oxygen evolution reaction. Herein, we fabricated Fe‐doped nickel oxalate (Fe‐NiC2O4) directly grown on nickel (Ni) foam as an efficient electrocatalyst for the alkaline oxygen evolution reaction using a facile one‐step hydrothermal method. Fe‐NiC2O4 served as a precursor for obtaining highly active Fe‐doped Ni oxyhydroxide (Fe‐NiOOH) via in situ electrochemical oxidation. Consequently, 0.75Fe‐NiOOH was demonstrated to be the optimal electrocatalyst, exhibiting outstanding oxygen evolution reaction activity with a low overpotential of 220 mV at a current density of 100 mA cm−2 and a Tafel slope of 20.5 mV dec−1. Furthermore, Fe‐NiOOH maintained its oxygen evolution reaction activity without performance decay during long‐term electrochemical measurements, owing to the phase transformation from nickel oxyhydroxide (NiOOH) to γ‐NiOOH (gamma nickel oxyhydroxide). These performances significantly surpass those of recently reported transition‐metal‐based electrocatalysts.

Nitrogen-Rich Covalent Organic Polymer for Metal-Free Tandem Catalysis and Postmetalation-Actuated High-Performance Water Oxidation.

Development of high-performing catalytic materials for selective and mild chemical transformations through adhering to the principles of sustainability remains a central focus in modern chemistry. Herein, we report the template-free assembly of a thermochemically robust covalent organic polymer (COP: 1) from 2,2'-bipyridine-5,5'-dicarbonyl dichloride and 2,4,6-tris(4-aminophenyl)triazine as [2 + 3] structural motifs. The two-dimensional (2D) layered architecture contains carboxamide functionality, delocalized π-cloud, and free pyridyl-N site-decked pores. Such trifunctionalization benefits this polymeric network exhibiting tandem alcohol oxidation-Knoevenagel condensation. In contrast to common metal-based catalysts, 1 represents a one of a kind metal-free alcohol oxidation reaction via extended π-cloud delocalization-mediated free radical pathway, as comprehensively supported from diverse control experiments. In addition to reasonable recyclability and broad substrate scope, the mild reaction condition underscores its applicability in benign synthesis of valuable product benzylidene malononitrile. Integration of 2,2'-bipyridyl units in this 2D COP favors anchoring non-noble metal ions to devise 1-M (M: Ni2+/ Co2+) that demonstrate outstanding electrochemical oxygen evolution reaction in alkaline media with high chronoamperometric stability. Electrochemical parameters of both 1-Co and 1-Ni outperform some benchmark, commercial, as well as a majority of contemporary OER catalysts. Specifically, the overpotential and Tafel slope (280 mV, 58 mV/dec) for 1-Ni is better than 1-Co (360 mV, 78 mV/dec) because of increased charge accumulation as well as a higher number of active sites compared to the former. In addition, the turnover frequency of 1-Ni is found to be 6 times higher than that of 1-Co and ranks among top-tier water oxidation catalysts. The results provide valuable insights in the field of metal-free tandem catalysis as well as promising electrochemical water splitting at the interface of task-specific functionality fuelling in polymeric organic networks.

In Situ Hydroxide Growth over Nickel-Iron Phosphide with Enhanced Overall Water Splitting Performances.

In this work, three dimensional (3D) self-supported Ni-FeOH@Ni-FeP needle arrays with core-shell heterojunction structure are fabricated via in situ hydroxide growth over Ni-FeP surface. The as-prepared electrodes show an outstanding oxygen evolution reaction (OER) performance, only requiring the low overpotential of 232mV to reach 200mAcm-2 with the Tafel slop of 40mVdec-1. For overall water splitting, an alkaline electrolyzer with these electrodes only requires a cell voltage of 2.14V to reach 1Acm-2. Mechanistic investigations for such excellent electrocatalytic performances are utilized by in situ Raman spectroscopy in conjunction with density functional theory (DFT) calculations. The computation results present that Ni-FeOH@Ni-FeP attains better intrinsic conductivity and the D-band center (close to that of the ideal catalyst), thus giving superior excellent catalytic performances. Likewise, the surface Ni-FeOH layer can improve the structural stability of Ni-FeP cores and attenuate the eventual formation of irreversible FeOOH products. More importantly, the appearance of FeOOH intermediates can effectively decrease the energy barrier of NiOOH intermediates, and then rapidly accelerate the sluggish reaction dynamics, as well as further enhance the electrocatalytic activities, reversibility and cycling stability.

Trace Iron-Doped Nickel-Cobalt selenide with rich heterointerfaces for efficient overall water splitting at high current densities

Developing bifunctional electrocatalysts based on non-precious metals for overall water splitting, while maintaining high catalytic activity and stability under high current densities, remains challenging. Herein, we successfully constructred trace iron-doped nickel–cobalt selenide with abundant CoSe2 (210)-Ni3Se4 (202) heterointerfaces via a simple one-step selenization reaction. The synthesized Fe-NiCoSex/NCFF (NCFF stands for nickel–cobalt-iron foam) exhibits outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity with low overpotentials of 328 mV for HER and 345 mV for OER at a high current density of 1000 mA cm−2, while maintaining stability for over 20 h. Additionally, the Fe-NiCoSex/NCFF exhibits the lowest Tafel slope values for both HER (33.7 mV dec-1) and OER (55.92 mV dec-1), indicating the fastest kinetics on its surface. The Fe-NiCoSex/NCFF features uniformly distributed micrometer-sized selenide particles with dense nanowires on their surface, providing a large reactive surface area and abundant active sites. Moreover, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses reveal that the catalyst is composed of nickel, cobalt, and iron, forming micrometer-sized particles with both crystalline and amorphous phases, thereby enhancing HER and OER performance under high current density. Density functional theory (DFT) calculations demonstrate that the heterostructure CoSe2 (210)-Ni3Se4 (202), with high electron density and suitable adsorption capacity for reaction intermediates, and low energy barriers for HER (−0.384 eV) and OER (ΔG1st: 0.243 eV, ΔG2nd: 0.376 eV), serves as an active center for both HER and OER.

Fe-Co Co-Doped 1D@2D Carbon-Based Composite as an Efficient Catalyst for Zn-Air Batteries.

A Fe-Co dual-metal co-doped N containing the carbon composite (FeCo-HNC) was prepared by adjusting the ratio of iron to cobalt as well as the pyrolysis temperature with the assistance of functionalized silica template. Fe1Co-HNC, which was formed with 1D carbon nanotubes and 2D carbon nanosheets including a rich mesoporous structure, exhibited outstanding oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities. The ORR half-wave potential is 0.86 V (vs. reversible hydrogen electrode, RHE), and the OER overpotential is 0.76 V at 10 mA cm-2 with the Fe1Co-HNC catalyst. It also displayed superior performance in zinc-air batteries. This method provides a promising strategy for the fabrication of efficient transition metal-based carbon catalysts.

Constructing heterogeneous interface between Co3O4 and RuO2 with enhanced electronic regulation for efficient oxygen evolution reaction at large current density

Exploring effective strategies for developing new high-efficiency catalysts for water splitting is essential for advancing hydrogen energy technology. Herein, Co3O4/RuO2 heterojunction interface is construct through ion exchange reaction and pyrolysis. The as-synthesized Co3O4/RuO2-4 exhibits outstanding oxygen evolution reaction (OER) activity at the current density of 100 mA cm−2 with a low overpotential of 276 mV, and remarkable stability (maintaining activity for 60 h at 100 mA cm−2). Experimental results and theoretical calculations reveal that the electrons around the heterogeneous interface transferred from RuO2 to Co3O4, resulting in electron redistribution and optimization of energy barriers for OER intermediates. This unique composite catalyst structure offers a new potential for designing efficient oxygen electrocatalysts at large current density.

Viologen-Cucurbit[7]uril Based Polyrotaxanated Covalent Organic Networks: A Metal Free Electrocatalyst for Oxygen Evolution Reaction.

Viologen-based covalent organic networks represent a burgeoning class of materials distinguished by their captivating properties. Here, supramolecular chemistry is harnessed to fabricate polyrotaxanated ionic covalent organic polymers (iCOP) through a Schiff-base condensation reaction under solvothermal conditions. The reaction between 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-diium dichloride (DPV-NH2) and 1,3,5-triformylphloroglucinol (TPG) in various solvents yields an iCOP-1 and iCOP-2. Likewise, employing cucurbit[7]uril (CB[7]) in the reaction yielded polyrotaxanated iCOPs, denoted as iCOP-CB[7]-1 and iCOP-CB[7]-2. All four iCOPs exhibit exceptional stability under the acidic and basic conditions. iCOP-CB[7]-2 displays outstanding electrocatalytic Oxygen Evolution Reaction (OER) performance, demanding an overpotential of 296 and 332mV at 10 and 20mA cm-2, respectively. Moreover, the CB[7] integrated iCOP-2 exhibits a long-term stable nature for 30h in 1m KOH environment. Further, intrinsic activity studies like TOF show a 4.2-fold increase in generation of oxygen (O2) molecules than the bare iCOP-2. Also, it is found that iCOP-CB[7]-2 exhibits a high specific (19.48mA cm-2) and mass activity (76.74mAmg-1) at 1.59V versus RHE. Operando-EIS study evident that iCOP-CB[7]-2 commences OER at a relatively low applied potential of 1.5V versus RHE. These findings pave the way for a novel approach to synthesizing various mechanically interlocked molecules through straightforward solvothermal conditions.

Carbon materials co-doped with nitrogen and sulfur for highly efficient catalytic activity in oxygen reduction and evolution

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) represent crucial steps in the functioning of fuel cells and metal-air batteries. Designing bifunctional oxygen electrode catalysts with high activity for both ORR and OER remains an immense challenge. In this study, we address this challenge by employing in-situ polymerization to design nitrogen and sulfur co-doped carbon materials (NSCs). The resulting NSC-1000–3 exhibits an onset potential of 1.03 V vs. RHE and a half-wave potential (E1/2) of approximately 0.89 V during ORR in an alkaline solution. When compared to commercial Pt/C, it demonstrates a positive shift of 60 mV in the half-wave potential. Furthermore, NSC-1000–3 displays outstanding oxygen evolution performance. At a current density of 10 mA cm−2, its performance matches that of RuO2. This material demonstrates exceptional performance in both ORR and OER, showcasing the synergistic doping effects of nitrogen and sulfur.

Superaerophilic/Superaerophobic NiFe-LDHs Electrode for Enhancing Overall Water Splitting in Alkaline Media.

Overall water splitting, as a critical approach to producing green hydrogen, is greatly impeded by the mass transfer of gaseous bubbles and dissolved gas molecules. Herein, a bifunctional superaerophilic/superaerophobic (SAL/SAB) NiFe layered-double-hydroxides (LDHs) electrode has been developed, which can drive H2 and O2 bubbles out of the reaction system by asymmetric Laplace pressure and accelerate dissolved gases diffusion through reducing their diffusion distance. Consequently, the SAL/SAB NiFe-LDHs electrode exhibits excellent HER activity with an overpotential of -76 mV at -10 mA cm-2 and outstanding oxygen evolution reaction activity with an overpotential of 253 mV at 100 mA cm-2. The bifunctional SAL/SAB NiFe-LDHs electrode is further utilized in overall water splitting, which can achieve 10 mA cm-2 with a cell voltage of 1.54 V. This work provides an efficient strategy to improve the efficiency of overall water splitting and can stimulate new electrode design in various gas-involved processes.

A high-efficiency NiFeSe4/NiSe2 bifunctional electrocatalyst with outstanding oxygen evolution reaction and overall water splitting performance

NiFeSe4/NiSe2-8 h had good overall water splitting performance. The heterostructure of the prepared NiFeSe4/NiSe2-8 h promoted the redistribution of electrons and improved the conductivity of the material.

Rapid microwave synthesis of medium and high entropy oxides for outstanding oxygen evolution reaction performance

The development of efficient and durable catalysts for the oxygen evolution reaction (OER) is urgent for renewable and sustainable energy storage and conversion.

Enhanced Photocatalytic Oxygen Evolution Using Copper-Coordinated Perylene Diimide Nanorod Assemblies.

A crystalline supramolecular photocatalyst is prepared through metal-induced self-assembly of perylene diimide with imidazole groups at the imide position (PDI-Hm). Exploiting the metal-coordination ability of imidazole, a crystalline assembly of copper-coordinated PDI-Hm (CuPDI-Hm) in a nanorod shape is prepared which displays an outstanding photocatalytic oxygen evolution rate of 25,900 μmol g-1 h-1 without additional co-catalysts. The imidazole-copper coordination, along with π-π stacking of PDI frameworks, guides the arrangement of PDI-Hm molecules to form highly crystalline assemblies. The coordination of copper also modulates the size of the CuPDI-Hm supramolecular assembly by regulating the nucleation and growth processes. Furthermore, the imidazole-copper coordination constructs the electric field within the PDI-Hm assembly, hindering the recombination of photo-induced charges to enhance the photoelectric/photocatalytic activity when compared to Cu-free PDI-Hm assemblies. Small CuPDI-Hm assembly exhibits higher photocatalytic activity due to their larger surface area and reduced light scattering. Together, the Cu-imidazole coordination presents a facile way for fabricating size-controlled crystalline PDI assemblies with built-in electric field enhancing photoelectric and photocatalytic activities substantially.