Hydrogen Precipitation Research Articles

Design Concepts of High-Entropy Materials for Zinc Ion Batteries.

Zinc-ion batteries have emerged as strong candidates for replacing Li/Na-ion batteries owing to their high safety and environmental friendliness. However, the large electrostatic repulsion between the cathode and Zn2+, the irreversible growth of zinc dendrites at the anode, and the hydrogen precipitation side reaction in the aqueous electrolyte have hindered the practical application of zinc ion batteries. Fortunately, the emergence of the revolutionary concept of high entropy has provided new opportunities for the development of battery materials. High-entropy materials, with their unique atomic structures and uniform distribution of multiple elements, offer flexible options for material compositions and electronic structures, thus attracting significant attention in battery systems. In this concept article, we summarize the definitions and intrinsic structural characteristics of high-entropy materials and provide a detailed overview of the latest design concepts from the perspectives of cathodes, anodes, and electrolytes. Finally, we outline the challenges faced by high-entropy materials and potential solutions to guide researchers in developing efficient and stable zinc-ion batteries.

Achieving the dendrite-free zinc anode by constructing a Sn-C interfacial layer with zincophilic and conductive network

Under the basic national policy of sustainable green development, high-performance and low-cost energy storage devices are urgently needed for intermittent generation of clean energy and storage of electrical energy. Zn metal with high capacity, abundant reserves and excellent plasticity, but the inevitable side reactions of the Zn metal anode itself have severely limited the development of aqueous Zn ion batteries (AZIBs) in the market. In this study, an artificial protective layer of polymer-derived carbon material combined with Sn is prepared to inhibit hydrogen precipitation and corrosion and prolong the lifetime of AZIBs. With these advantages, the Zn@Sn@N doped carbon (Zn@CNS) symmetric cell could achieve a stable cycle life of 1000 h at 2 mA cm−2 and low overpotential. The excellent stripping life of over 400 h is achieved in half-cells assembled with Cu foils. Furthermore, the α-MnO2//Zn@CNS full battery shows superior stability in rate capability and long-term capacity retention compared to the α-MnO2//Zn battery, indicating that the CNS coating provides excellent performance and practical value.

Recent Progress on Cobalt‐Based Heterogeneous Catalysts for Hydrogen Production from Ammonia Borane

AbstractAmmonia borane (NH3BH3, AB) is a quintessential exemplar of chemical hydrogen storage materials and has been widely used in hydrogen evolution. Although expensive metal catalysts (such as Rh, Ru, Pt, Ag, etc.) exhibit high activity in the hydrolysis of ammonia borane, inexpensive metals are more economical. Cobalt (Co), in particular, is not only relatively inexpensive and readily available, but also possesses high activity and selectivity. Compared to other catalysts, cobalt‐based catalysts have better durability and can maintain catalytic activity for a longer period of time, making them favored by researchers. These catalysts demonstrate excellent stability, hydrogen evolution rate, and turn over frequency. This article summarized previous progress in low price metal cobalt‐based catalysts for hydrogen precipitation from ammonia borane, focusing on cobalt‐based catalysts supported on various supports, especially those supported on carbon materials, metal oxides, MOFs, and nickel foams. The characteristics of high‐performance catalytic systems are analyzed in detail. The development prospects of Co catalysts for hydrogen production from ammonia borane were also discussed. In summary, this review compiles various supported and other types of cobalt based catalysts in recent years, and also identifies the existing problems with these catalysts, providing a reference for developers to study these catalysts. It is believed that through careful regulation of the electronic and spatial structures of Co based catalysts, well‐designed Co based non precious metal catalysts will play a significant role in the decomposition of ammonia borane.

Organic Electrolyte Additives for Aqueous Zinc Ion Batteries:Progress and Outlook.

Aqueous zinc ion batteries (AZIBs) are considered one of the most prospective new-generation electrochemical energy storage devices with the advantages of high specific capacity, good safety, and high economic efficiency. Nevertheless, the enduring problems of low Coulombic efficiency (CE) and inadequate cycling stability of zinc anodes, originating from dendrites, hydrogen precipitation and passivation, are closely tied to their thermodynamic instability in aqueous electrolytes, which significantly shortens the cycle life of the battery. Electrolyte additives can solve the above difficulties and are important for the advancement of affordable and reliable AZIBs. Organic electrolyte additives have attracted widespread attention due to their unique properties, however, there is a lack of systematic discussion on the performance and mechanism of action of organic electrolyte additives. In this review, a comprehensive overview of the application of organic electrolyte additives in AZIBs is presented. The role of organic electrolyte additives in stabilizing zinc anodes is described and evaluated. Finally, further potential directions and prospects for improving and directing organic electrolyte additives for AZIBs are presented.

Effect mechanism of Cd on band structure and photocatalytic hydrogen production performance of ZnS

ZnS is widely used in the photocatalytic decomposition of water to produce hydrogen due to its fast electron-hole pair generation and high negative potential. However, its absorption in the visible region is poor due to its wide band gap, and it has serious photogenerated carrier recombination problems. Herein, a shallow impurity energy level was introduced by doping the ZnS lattice with Cd. Due to its presence, electrons trying to return to the valence band are trapped and excited twice, suppressing the recombination of photogenerated carriers and greatly improving electron utilization. The Cd1.5-ZnS possesses a hydrogen production rate as high as 85722.20 μmol/g, which is 17 times higher than pure ZnS. Meanwhile, Cd1.5-ZnS has a narrower forbidden band and superior visible light absorption, and the serious photocorrosion problem of ZnS has been suppressed. This study provides a viable approach for the synthesis of photocatalysts with adjustable band gaps and enhanced hydrogen precipitation efficiency.

Construction of electrospun multistage ZnO@PMIA gel electrolytes for realizing high performance zinc-ion batteries

As an important component of ZIBs, flexible gel electrolytes offer the advantages of solid/liquid electrolytes and good interfacial bonding. However, limited by poor ionic conductivity and mechanical properties, traditional gel electrolytes are still unable to meet realistic applications. To solve the above problems, in this paper, poly(m-phenylene isophthalamide) (PMIA) nanofiber membranes were prepared by electrospinning, and then ordered zinc oxide (ZnO) nanorods were grown on their surfaces by hydrothermal method, and ZnO@PMIA nanofiber membranes were combined with poly(vinyl alcohol) (PVA) gel to obtain ZnO@PMIA-PVA (ZPP) composite electrolytes. On the one hand, thanks to the advantages of large specific surface area and good electrical conductivity of PMIA nanofibers and ZnO nanorods, they can provide continuous and uniform transmission channels for Zn2+ .On the other hand, ZPP combines the nanofiber layer with the gel layer, which possesses excellent mechanical properties and produces a well-bonded interface with the electrode, which can effectively reduce the internal resistance and resist the penetration of the dendrimer into the electrolyte during long cycling. The results show that the ZPP composite electrolyte has a high ionic conductivity (18.3 mS·cm-1) and exhibits obvious advantages in inhibiting hydrogen precipitation and oxidative decomposition of Zn anode, and the Zn/ZPP/Zn symmetric battery can be recycled for >1000 h at 3 mA·cm-2, and the full battery Zn/ZPP/MnO2 can still maintain 159.3 mAh·g-1 residual capacity after 1000 cycles with stable long-cycle performance and high coulombic efficiency (CE) (99 %). This flexible composite electrolyte has high safety, mechanical and electrochemical properties, which can realize high-performance ZIBs, and is expected to provide a new strategy for next-generation wearable energy storage devices.

Modulation of Al-Zn-0.5Sn-0.5Mn anode properties by trace Sb

In aluminum-air batteries, hydrogen precipitation corrosion is a difficult problem for aluminum anodes in alkaline electrolytes, which causes a decrease in the efficiency and shortens the service life of aluminum anodes. Under the condition of 4 mol·L-1 NaOH alkaline solution, the addition of trace Sb (0.04 wt%) to Al-Zn-0.5Sn-0.5Mn resulted in an increase of 88.64% in energy density and 74.03% in the specific capacity of the aluminum anode, and a constant current discharge at a current density of 10 mA·cm-2, with a discharge voltage as high as 1.43 V and the discharge process is stable, the anode efficiency reaches 90.90% and the energy density reaches 2526 Wh·kg-1. The improvement in the performance of the aluminum anode is mainly due to the precipitation of the AlSb phase, which activates the grain boundaries, improves the electrochemical activity of the aluminum anode, and forms Sb-containing membranes to inhibit the formation of surface passivation films. Efficient discharge in alkaline solution and long battery life.

The catalytic enhancement of the hydrogen evolution reaction facilitated by Pd coating on SrTiO3

The wide bandgap structure of 3.2 eV has made SrTiO3 (STO) well-known for its exclusive responsiveness to ultraviolet (UV) light. By anchoring Pd to the surface oxygen atoms of STO, we have successfully reduced the forbidden bandwidth of STO to 2.75 V, thereby extending its light absorption range to visible light. Simultaneously, trace amounts of low-valent Pd were distributed on the surface, significantly enhancing the photocatalytic hydrogen precipitation rate to 7366.07 μmol·g-1·h-1. This innovative approach led to the development of a novel nanocatalyst with numerous tailored active sites specifically designed for efficient photocatalytic hydrogen evolution. X-ray fine spectroscopy confirms Pd was successfully anchored to the STO surface and coordinated with surface O and the occurrence of Pd and Pd coordination at 2.0 Å from the Pd center in the R-space. Density functional theory (DFT) calculations further validate that anchoring Pd onto the STO surface reduces the free energy of adsorption for H* on these active sites. This discovery presents a promising strategy for immobilizing metal catalysts at perovskite STO’s unit sites.

Graphdiyne Nanosheets Integrated with Ni6MnO8 via In Situ Calcination: A Robust S‐Scheme Heterojunction for Enhanced Eosin Y‐Sensitized Photocatalytic Hydrogen Production

As a 2D semiconductor material, graphdiyne (GDY) is a promising photocatalyst with excellent carrier mobility, uniform pores, ideal light absorption, and appropriate bandgap structure. Herein, GDY nanosheets are prepared by mechanical ball milling and subsequently tightly bonded to Ni6MnO8 by the in situ calcination method. The constructed Ni6MnO8/GDY S‐scheme heterojunction exhibits excellent photocatalytic performance. Under visible light, with eosin Y as the sensitizer, the hydrogen evolution of the optimized component reaches 1719.2 μmol (g h)−1, representing 3.6 and 9.6 times enhancement in comparison with that of Ni6MnO8 and GDY, respectively. The in situ calcination method is thought to play a major role in improving the efficiency of hydrogen evolution, which can enhance the interactions between the materials without significantly reducing the specific surface area of the materials. The presence of an internal electric field in the composite catalyst facilitates the separation and migration of photogenerated carriers. Furthermore, an S‐scheme heterojunction charge transfer model with Ni6MnO8 as the active site for hydrogen precipitation is rationally constructed by in situ X‐ray photoelectron spectroscopy, thereby revealing the migration path of photogenerated carriers. The results provide a new strategy for the construction of GDY‐based photocatalytic composite catalysts with exceptional potential for hydrogen generation.

Construction of 2D/2D S-scheme Bi2MoO6/Zn-TCPP heterojunction via in-situ self-assembly growth strategy to enhance interface effect for efficient photocatalytic hydrogen production

Two-dimensional/two-dimensional (2D/2D) heterojunctions are considered to be an effective strategy for forming strong interface effects and facilitating photogenerated carrier separation. However, it is usually limited by the size mismatch of the materials, even at the expense of its redox capability. Herein, 2D/2D S-scheme heterojunction photocatalyst Bi2MoO6/Zn-TCPP (BMO/ZTP) composed of 2D Bi2MoO6 and 2D Zn-TCPP (TCPP: tetrakis (4-carboxyphenyl) porphyrin) (MOFs) was constructed by in-situ self-assembly growth strategy. The size-compatible 2D/2D composites had abundant surface active sites and strong interactions. In addition, band bending and interfacial electric field (IEF) effect based on S-scheme heterojunction could accelerate the separation and migration of photogenerated carriers in BMO/ZTP. The best hydrogen precipitation rate of the BMO/ZTP was 10900.94 umol·g−1·h−1, which was 38.90 and 3.24 times higher than that of Bi2MoO6 (280.26 umol·g−1·h−1) and Zn-TCPP (3360.34 umol·g−1·h−1), respectively. The results indicated that 2D/2D BMO/ZTP S-scheme heterojunction could enhance the interface effect and retain strong reducing electrons to achieve efficient photocatalytic hydrogen production, which was confirmed by ultraviolet photoelectron spectroscopy (UPS), Tafel curve, electron spin resonance (ESR) and time-resolved photoluminescence (TRPL) characterization and density functional theory (DFT) calculations. This work provided a general strategy for constructing 2D Bi2MoO6 and 2D MOFs S-scheme heterojunctions to enhance interface effects for achieving efficient photocatalytic hydrogen production.

Facile synthesis of hierarchical core-shell carbon@ZnIn2S4 composite for boosted photothermal-assisted photocatalytic H2 production

Against the backdrop of energy shortage, hydrogen energy has attracted much attention as a green and clean energy source. In order to explore efficient hydrogen production pathways, we designed a composite photocatalyst with carbon-based core-shell photothermal-assisted photocatalytic system (Carbon@ZnIn2S4, denoted as C@ZIS). The well-designed catalyst C@ZIS composites demonstrated a photocatalytic hydrogen precipitation rate of 2.97 mmol g-1 h−1 even in the absence of the noble metal Pt co-catalyst. The incorporation of carbon-based core-shell photocatalysts into a photocatalytic reaction significantly affects the activity of the reaction by triggering a photothermal effect in the reaction solution. The results of the physicochemical experiments demonstrated that the carbon spheres in C@ZIS composite system could provide a greater number of active sites, thereby accelerating the electron transfer and separation efficiency, and thus enhancing the photocatalytic activity. The study presents an efficacious design concept for the development of efficacious carbon-based core-shell photothermal-assisted photocatalysts, which is anticipated to facilitate the efficient conversion of solar energy to hydrogen energy.

Experimental research of electrolyte additives and battery performance of aqueous zinc-ion batteries

Abstract Aqueous zinc-ion batteries (AZBs) have received increasing attention due to their high safety, high theoretical specific capacity, and abundant resources. However, the problems of zinc anode dendrite growth, hydrogen precipitation corrosion, and irreversible side reactions in AZIBs have restricted their application process. Electrolyte additives are an effective way to solve problems. This work looked at what would happen when 4-(2-hydroxyethyl) piperazine-1-ethane sulfonic acid (HEPES) was added to the ZnSO4 solution, which is the electrolyte. It was tested on AZIBs by using coin batteries as the carriers and adding HEPES to the electrolyte. The findings demonstrated that the electrolyte exhibited robust stability following HEPES addition, effectively suppressing dendrite growth through electric field modulation at the zinc anode. Incorporating 8 mM HEPES notably enhanced battery cycle longevity to over 240 hours under conditions of 0.2 mA cm−2 and 0.2 mAh cm−2. The HEPES additive was found to be effective in improving the rate capability through the testing of Zn||Zn symmetric batteries. This work provides a feasible idea for the performance improvement of low-cost and high-efficiency AZIBs.

In situ oxidative growth to form compact TiO2–Ti3C2 heterojunctions for photocatalytic hydrogen evolution

Solar photocatalytic hydrogen production shows promise in addressing global energy and environmental concerns. The limited efficiency of photocatalysts is mainly due to ineffective separation and transfer of photogenerated charges. To improve this, we enhance the TiO2–Ti3C2 heterojunction by in-situ oxidation through interfacial engineering, resulting in a more compact composition. Subsequently, we anchor single-atom Pt at the TiO2–Ti3C2 interface through photo-Ti3C2 reduction. The in-situ growth of TiO2 on Ti3C2 introduces an interfacial driving force for carrier separation and provides a channel for electron transfer from TiO2 to Ti3C2. This further facilitates transfer onto Pt, shortening the migration distance and enhancing the photocatalytic efficiency. The best Pt/TiO2–Ti3C2 composite demonstrates an impressive hydrogen precipitation efficiency of 767 μmol g−1 h−1, surpassing TiO2 and Pt/TiO2 by factors of 12 times and 1.46 times, respectively. Furthermore, we developed a higher efficiency photocatalyst using the molten salt method to avoid the risks associated with conventional hydrofluoric acid etching. This research opens up new possibilities for the preparation of MXenes interface-modified catalysts, offering a valuable avenue for future exploration in the field.

High-performance photocatalytic hydrogen evolution in a Zn0.5Cd0.5S/MoS2 p–n heterojunction

With respect to solid-solution photocatalysts for water splitting, researchers have focused on improving the loading and stability of catalysts, which have been major concerns and research interests. Herein, the fabrication of Zn0.5Cd0.5S/MoS2 nanocomposites involved a two-step method that encompassed hydrothermal synthesis and physical mixing. Experimental results confirmed that the Zn0.5Cd0.5S/MoS2 nanocomposites exhibited outstanding photocatalytic performance. In particular, they exhibited a notable hydrogen precipitation rate of 19.41 mmol/(g*h). The hydrogen production performance of Zn0.5Cd0.5S/MoS2 was approximately nine times greater than that of pure Zn0.5Cd0.5S, indicating a considerable increase. The observed enhancement in photocatalytic efficiency can be attributed to the formation of a p–n heterojunction between Zn0.5Cd0.5S and MoS2. This particular junction helped in separating and migrating photoinduced charge carriers, ultimately improving the photocatalytic performance. Furthermore, the addition of excess thiourea in MoS2 preparation produced Mo–O defects and increased the layer spacing of the involved material, improving the electron transfer and visible-light utilization of the material. The inhibition of carrier recombination was beneficial for synthesizing efficient and long-lasting photocatalysts.

Screening and comparison of 18 transition metal atoms doped to modulate the electrocatalytic synthesis of ammonia with multi-S vacancies MoS2: A study of density functional theory

Electrocatalytic nitrogen reduction reaction (NRR) represents a promising approach for the sustainable production of ammonia (NH3). However, current electrocatalysts exhibit limitations in terms of active sites, high reaction potential, and poor reaction selectivity. Consequently, there is a pressing need for the development of NRR electrocatalysts with high activity and selectivity under mild conditions. Among them, defect engineering and transition metal doping are two effective methods to improve the electronic structure of catalysts. In this paper, density functional theory was used to study the activity of electrocatalytic NRR on Molybdenum disulfide (MoS2) surfaces with 1–4 S vacancy numbers (VSx–MoS2, x = 1–4) and transition metal (TM)-doped VS3–MoS2 (TM@VS3–MoS2). Both VSx–MoS2 showed better structural stability, with S vacancy defects altering the electronic structure of the surface. As more Mo atoms were exposed on the surface of the structure, the adsorption of N2 gradually enhanced and the reaction was more inclined to undergo NRR. Further investigation of 18 TM-doped VS3–MoS2 revealed that the doping of Sc, Ti, V, Y, Zr and Nb atoms effectively inhibits the hydrogen precipitation reaction and reduced the energy of NH3 desorption, which contributed to the continuation of the reaction. Therefore, the improvement of MoS2 electrocatalytic NRR performance can be achieved by constructing S vacancies and TM doping to provide a better basis and reference for experimental exploration.

Monolayer BiOI doped with nonmetals (B, C, N, Si, P, S) to enhance photocatalytic hydrogen precipitation performance

Efficient photocatalysts play a crucial role in producing green and clean hydrogen energy. BiOI is a good material for photocatalytic hydrogen generation. However, the low position of the conduction band also affects its redox ability. We studied the electronic structure and hydrogen evolution reaction (HER) catalytic performance of six nonmetals doped BiOI based on the first principles calculation. The relationship between doping elements and catalytic performance was explained. We used the DFT + U method to find that the band gap values of X-BiOI (X = B, C, N, Si, P, S) are 1.99 eV, 1.23 eV, 1.73 eV, 2.08 eV, 1.40 eV and 1.77 eV, respectively. After nonmetal doping, the bottom position of the conduction band of BiOI rises, which enhances the reduction ability. Specifically, the impurity energy levels generated in the band gap of B and Si doped BiOI reduce the recombination rate of photogenerated carriers, and lower the work function to 5.62 eV and 5.45 eV, respectively. Studies on hydrogen production performance show that B-doped BiOI has the strongest reduction ability and the best catalytic effect, with the lowest ΔGH* (1.57 eV). This research provides some ideas for understanding nonmetal doped materials for the photocatalytic hydrogen evolution system.

Construction of the VOBiOBr/VSZnIn2S4 heterojunction for photocatalytic hydrogen production and dye removal under simulated sunlight

Semiconductor photocatalysis is a promising method for utilizing solar energy to decompose water and degrade pollutants. However, the limited visible light absorption capacity and high carrier complexation rate hinder the utilization of sunlight for photocatalysts. The study prepared VOBiOBr/VSZnIn2S4 S-scheme heterojunction photocatalysts with sulfur and oxygen vacancies using a two-step solvothermal method. The photocatalyst was then used to simulate sunlight decomposition of water for hydrogen production and degradation of dye wastewater. Characterisation tests revealed that the incorporation of sulfur and oxygen vacancies effectively enhanced the visible light absorption of BiOBr and ZnIn2S4. The construction of S-scheme heterojunction resulted in an improvement in visible light absorption capacity, as well as the promotion of separation and migration of photogenerated carriers. The study demonstrates that VOBiOBr/VSZnIn2S4 exhibits superior hydrogen precipitation and degradation properties compared to BiOBr/ZnIn2S4 without S and O vacancies and VSZnIn2S4 without a heterojunction when subjected to simulated sunlight irradiation. The results of the tests and mechanistic analyses suggest that the synergistic effect of S and O vacancies and heterojunction enhances the photocatalytic performance. This study offers novel perspectives on the production of multifunctional photocatalysts that effectively utilize sunlight.

Fabrication of 0D/2D amorphous NixB/ZnIn2S4 S-scheme for enhanced photocatalytic hydrogen evolution performance

The design and synthesis of low-cost hydrogen evolution photocatalysts with high carrier separation capability and visible light responsiveness are key factors in increasing hydrogen production. In this work, zero-dimensional (0D) amorphous nickel boride (NixB) was synthesized using a reduction method. Subsequently, a 0D/2D amorphous NixB/ZnIn2S4 S-scheme heterojunction was fabricated through electrostatic attraction. This heterojunction exhibited stronger visible light responsiveness and enhanced photogenerated carrier separation performance. The morphology, composition, elemental, structural, and light absorption capacities of the as-synthesized composites were researched by SEM, TEM, XRD, XPS, and UV–vis DRS. The ability to separate photogenerated carriers were evaluated through photoelectrochemical experiments. The hydrogen evolution rate of NixB/ZnIn2S4 (2208 μmol h−1 g−1) increased 25 times than that of single ZnIn2S4 in sacrificial solution, and the apparent quantum yield (AQY) at 400 nm was 14.25 %. This study gives evidence of the great preponderance of S-scheme heterojunction and multidimensional material co-construction in improving hydrogen precipitation.

Anode-Free Aqueous Aluminum Ion Batteries.

Aqueous aluminum ion batteries (AAIBs) possess the advantages of high safety, cost-effectiveness, eco-friendliness and high theoretical capacity. However, the Al2O3 film on the Al anode surface, a natural physical barrier to the plating of hydrated aluminum ions, is a key factor in the decomposition of the aqueous electrolyte and the severe hydrogen precipitation reaction. To circumvent the obnoxious Al anode, a proof-of-concept of an anode-free AAIB is first proposed, in which Al2TiO5, as a cathode pre-aluminum additive (Al source), can replenish Al loss by over cycling. The Al-Cu alloy layer, formed by plating Al on the Cu foil surface during the charge process, possesses a reversible electrochemical property and is paired with a polyaniline (cathode) to stimulate the battery to exhibit high initial discharge capacity (175 mAh g-1), high power density (≈410Wh L-1) and ultra-long cycle life (4000 cycles) with the capacity retention of ≈60% after 1000 cycles. This work will act as a primer to ignite the enormous prospective researches on the anode-free aqueous Al ion batteries.

Coal-based carbon quantum dots modified Ni-MOF and Co/Zr-MOF heterojunctions for efficient photocatalytic hydrogen evolution

NS-CQDs were synthesized by a hydrothermal method using high-sulfur lignite as the carbon source. Modification of Ni-MOF and Co/Zr-MOF using NS-CQDs to explore the performance of composite photocatalysts for hydrogen production. It was found that NS-CQDs significantly enhanced the hydrogen precipitation performance of the composite photocatalysts compared with the MOFs catalysts alone, and the highest hydrogen precipitation rate of the novel composite photocatalyst 5%NS-CQDs/NCZ2 reached 3662.68 μmol g−1 h−1. It can be inferred from the conduction band and valence band positions of Ni-MOF, Co/Zr-MOF and NS-CQDs that a double S-type heterojunction is formed. The presence of thiophene and pyrrole nitrogen in NS-CQDs can promote electron transport, reduce the rate of electron-hole pair complexation, and improve the hydrogen evolution activity of the 5%NS-CQDs/NCZ2.