Hierarchical Porous Structure Research Articles

A hierarchical porous structure and nitrogen-doping jointly enhance the lithium-ion storage capacity of biomass-derived carbon materials

Biomass-derived carbon materials are considered potential lithium-ion anode materials because they are sustainable, renewable, economical, and environmentally friendly and have tunable microstructures. However, biomass-derived carbon materials have low specific capacity and show capacity degradation during long-term electrochemical cycling, which prevents their application in high-performance lithium-ion batteries. Hence, in this paper, nitrogen-doped hierarchical porous carbon (NHPC) is synthesized from a biomass waste material, corncob, through one-step activation and carbonization procedures. N-doping in the NHPC modifies the electron distribution on the surface of carbon, resulting in the generation of additional lithium-ion storage sites and enhancing electrode wettability to increase the conductivity. Additionally, the doping procedure results in a hierarchical porous structure with an increased specific surface area and pore volume, which facilitates ion transport and provides remarkable cycling stability. The electrochemical performance of NHPC is improved by the jointly beneficial combination of N-doping and the hierarchical porous structure. The optimized NHPC electrode provides a reversible specific capacity of 700 mAh g−1 after 100 cycles at 100 mA g−1. This study provides a simple and efficient method for improving the electrochemical properties of biomass-derived carbon materials through elemental doping and modulation of microscopic morphology and structure.

Thermal insulated C/SiC nanofiber aerogel with high thermal stability and superior electromagnetic wave absorption performance

Integration of thermal insulation and electromagnetic wave absorption was crucial in stealth technology and hypersonic vehicles but challenging. Herein, silicon carbide nanofibers were synthesized by in situ chemical vapor deposition within a carbon foam skeleton to form a wave absorbing and heat insulating integrated composite aerogel with a hierarchical porous structure. The unique hierarchical porous structure provided an excellent platform for the absorption of electromagnetic waves, achieving a minimum reflection loss (RLmin) of −51.46 dB at 17.20 GHz. Meanwhile, the C/SiC nanofiber aerogel maintained a low density of 0.013 g/cm3, an ultra-low thermal conductivity of 0.030 W/(m⋅K) and a high thermal stability up to 1000 °C. Furthermore, to enhance the electromagnetic wave (EMW) absorption property of the aerogel, polypyrrole (PPy) was coated on the surface of C/SiC nanofiber aerogel by facile impregnation and chemical polymerization. The multiple conductor-semiconductor-conductor structure of C/SiC-PPy composite aerogel leads to various EMW loss mechanisms and excellent impedance match, resulting in an outstanding EMW absorption performance, with a RLmin of −60.31 dB at 2.96 GHz.

Achieving high-efficiency electromagnetic wave absorption performance in a 3-layer hierarchical porous magneto-dielectric nanocomposite

Hierarchical porous structures along with micro- and nanoparticles of magneto-dielectric components in sandwich structure design have superior potential applications in the field of electromagnetic wave absorption, due to high active dissipation phenomena such as multiple scatterings and reflections between components, 3D network pores and layers, coupling interactions between each layer, promotion of interfacial polarization, and so on. The Sandwich-Structure absorber composed of hierarchical porous Bi2MoO6, Cu microparticles, and FeNi nanoparticles was effectively constructed with optimization in layer thickness and low filler loading percentage. The microwave absorption characteristics of absorber samples varied in thickness but all less than 1.6 mm in total thickness were thoroughly examined. The as-prepared sandwich structure displayed a unique microwave absorbing behavior due to the multiple-layer structure, the dielectric dissipation property of both Bi2MoO6, Cu microparticles and the magnetic dissipation feature of FeNi nanoparticles, as well as the complementary effect between particles and layers. Minimum reflection loss (RLmini) of −45.5 dB at 5.5 GHz is obtained with proper optimization of layer order and thickness in a resin base 3-layer absorber sample with Bi2MoO6 placed as a top layer with 0.4 mm thickness, FeNi placed as a middle layer with 0.5 mm thickness, and finally Cu placed as a bottom layer with 0.7 mm thickness. The results show that the as-prepared 3-layer nanocomposite sample has a high potential for usage in microwave absorption in the low-frequency band.

Chemical etching optimization of 3D printed α-Al2O3 monoliths to enhance the catalytic applications

Direct Ink Writing has been demonstrated to be a promising route to produce ceramic catalysts with complex geometries and enhanced catalytic performances. To increase the catalytic performances, chemical etching can be conducted to get an interconnected and hierarchical porous structure, to increase the surface area and the contact time of the reactants. In this work, DIW alpha (α)-Al2O3 catalysts were chemically etched with hydrofluoric acid (HF). Several combinations of acid concentrations and etching times were studied to find the optimal etching condition. For HF concentration of 5, 20 and 40 wt%, the optimal etching time was 48, 24 and 5 h, respectively, being 40 wt% the concentration that shows the greatest increase of surface porosity (of around 5%). HF etching can produce an interconnected porosity on 3DP α-Al2O3, but it does not yield improvement in catalytic performances when the content of fluor (F) is higher than 10 at% since it produces parasite reactions.

Unravelling the synergistic effects in GdCe composite oxides supported biochar catalysts for formaldehyde elimination: Elevated performance and SO2 toleration

A chain of GdCe oxides boosted biochars derived from maize straw and sewage sludge (GdyCe1-y/MPBs) were fabricated for formaldehyde (HCHO) catalytic decomposition. The ingenerate relationship between the abatement performance and corresponding structural feature was comprehensively evaluated by XPS, in situ DRIFTS, BET, XRD, SEM and H2-TPR. Meanwhile, 10%Gd0.25Ce0.75/MPB exhibited excellent performance, favorable SO2 and moisture toleration over a broad temperature range from 160 to 320 ℃, where it achieved 96.8% removal efficiency with 90.5 % selectivity at 200 ℃. The single or united effects of O2, SO2, H2O on HCHO abatement over 10 %Gd0.25Ce0.75/MPB were tested, and the findings demonstrated that the suppressive effects of SO2 and H2O outweighed the promoting influence of O2 within a specific range. Gd and Ce co-modified MPB revealed superior HCHO removal capability in contrast to that of Gd or Ce severally modified MPB, ascribing to the synergistic effect of GdOx and CeOx and benefitting from the augmentation of surface area and total pore volume, the aggrandizement of surface active oxygen species, the promotion of redox ability and the inhibition crystallization of CeOx. According to in situ DRIFTS, a series of intermediates including formate species and dioxymethylene (DOM) were produced, which would eventually decompose into H2O and CO2. In addition, the mass transfer and diffusion of the reactants along with the accessibility of the catalytic sites were enlarged by the hierarchical porous structure of the support, which were also answerable for its distinguished catalytic performance. Furthermore, 10%Gd0.25Ce0.75/MPB possessed remarkable potential for industrial applications.

Hierarchical Porous N-Doped Carbon Particles Derived from ZIF-8 as Highly Efficient H2S Selective Oxidation Catalysts.

In the selective oxidation of H2S, the catalytic activity over N-doped carbon-based catalysts is significantly influenced by the accessibility of active sites and the mass transfer rates of reactant molecules (e.g., H2S and O2) as well as generated sulfur monomers. Therefore, it is crucial for enhancing the initial performance via the controlled synthesis of carbon-based catalysts with highly exposed active sites and unique porous structures. Herein, we reported on an efficient strategy to synthesize nanosized N-doped carbon particles with hierarchical porous structures by directly pyrolyzing an oversaturated NaCl-encapsulated ZIF-8 precursor mixture. The introduction of NaCl not only serves as a pollution-free template to promote the formation of graphitic carbon layers but also acts as an intercalating agent to guide the derivation of hierarchical porous structures, as well as enhances the amount of active nitrogen species in the catalysts. As a result, the as-prepared H-NC800 catalyst shows excellent H2S selective oxidation performance (sulfur formation rate is 794 gsulfur·kgcat-1·h-1), good stability (>80 h), and antiwater vapor properties. The characterization results and DFT calculations indicate the crucial role of pyridinic N in the adsorbing and activating reactant molecules (H2S, O2). Furthermore, nanoscale N-doped carbon particles accelerated the rapid transport of generated sulfur monomers under a hierarchical porous structure. This investigation introduces a distinctive strategy for synthesizing ZIF-8-derived N-doped carbon nanosized with a hierarchical porous structure, while its efficient and stable H2S selective oxidation performance highlights significant potential for practical implementation in the industrial desulfurization process.

High transition kinetics enabling high Zn utilization for high-capacity and long-lifespan nickel-zinc battery

Aqueous nickel-zinc (Ni-Zn) battery is one promising grid energy storage device owing to its high theoretical energy density, high safety and low cost. However, the large-scale commercialization of Ni-Zn battery is significantly hindered by its low practical energy density and poor cycle lifespan caused by the low reversibility and transition kinetics between the metallic Zn and ZnO with low Zn utilization. To address these issues, a type of hierarchical porous Indium-doping ZnO micro-bowls (In-ZnO) is constructed through an in-situ chemical corrosion strategy. The abundant voids and pores facilitate the ionic transport, and simultaneously accommodate the volumetric expansion during the electrochemical transition between metallic Zn and ZnO. Density functional theory calculations further reveal that In-ZnO achieves the enhanced electrical/ionic conductivity and improved adsorption to OH–, accelerating the solid–liquid transitions of Zn-Zn(OH)42- and Zn(OH)42--ZnO, as well as the solid–solid transition of Zn-ZnO. Simultaneously, the Indium-doping inhibits the hydrogen evolution and passivation. Ascribed to the synergetic effect of the hierarchical porous structure and Indium-doping, the In-ZnO electrode demonstrates ultra-stable capacity retention of 98.6% over 1000 cycles at 9 A g-1 under 92.3% Zn utilization, and high capacity of 590.2 mAh g-1 even at high current density of 36 A g-1.

Fabrication of Laser-Induced Graphene on Carbon Electrodes for Efficient Hydrogen Evolution Reaction

Hierarchical porous carbon materials have received significant attention for application in catalytic water splitting because of their high efficiency, cost-effectiveness, and biocompatibility. In this study, laser-induced graphene (LIG) was fabricated on a carbon film- (CF-) type substrate for an efficient hydrogen evolution reaction (HER). The LIG-CF electrode was fabricated via laser-induced graphitization on a commercial polyimide (PI) film, followed by the pyrolysis of the LIG on the PI film (LIG-PI). During pyrolysis, the microscopic and material properties of the LIG remained intact, as verified through various characterizations. The as-prepared all-carbon electrode was then utilized as an electrode for the HER study in a 1.0 M KOH electrolyte and compared with LIG-PI and Pt electrodes. In the HER experiments, the optimized LIG-CF electrode exhibited excellent catalytic performance with zero-onset potential, and the potentials required to achieve high current densities of 10 and 20 mA/cm2 were 134 and 139 mV (vs. reversible hydrogen electrode (RHE)), respectively. The excellent performance of the LIG-CF electrode originates from the hierarchical porous structure of the LIG material, which serves as an electrochemically active site, and carbon substrate that facilitates the fast transport of ions at the electrode/electrolyte interface. Additionally, the carbon substrate shortens the transportation length of electrons which played a significant role for the enhanced performance of the LIG-CF electrode.

Precise Construction of Nitrogen-Enriched Porous Ionic Polymers as Highly Efficient Sulfur Dioxide Adsorbent.

Porous ionic polymers with unique features have exhibited high performance in various applications. However, the fabrication of functional porous ionic polymers with custom functionality and porosity for efficient removal of low-concentration SO2 remains challenging. Herein, a novel nitrogen-enriched porous ionic polymer NH2Py-PIP is prepared featuring high-content nitrogen sites (15.9wt.%), adequate ionic sites (1.22mmolg-1), and a hierarchical porous structure. The proposed construction pathway relies on a tailored nitrogen-functionalized cross-linker NH2Py, which effectively introduces abundant functional sites and improves the porosity of porous ionic polymers. NH2Py-PIP with a well-engineered SO2-affinity environment achieves excellent SO2/CO2 selectivity (1165) and high SO2 adsorption capacity (1.13mmolg-1 at 0.002bar), as well as enables highly efficient and reversible dynamic separation performance. Modeling studies further elucidate that the nitrogen sites and bromide anions collaboratively promote preferential adsorption of SO2. The unique design in this work provides new insights into constructing functional porous ionic polymers for high-efficiency separations.

N, O-codoped porous carbon fiber cloth synthesized by molecular dispersed CaCl2·6H2O in situ activation for high performance supercapacitors

In this study, a nitrogen/oxygen co-doped carbon fiber cloth with a hierarchical porous structure was synthesized by one-step carbonization and in situ activation method and acted as binder-free electrode materials for supercapacitors. Cotton fiber cloth served as the carbon precursor, while molecular dispersed CaCl2·6H2O and urea functioned as activator and N dopant, respectively. The influence of molar concentration of CaCl2·6H2O and urea on the microstructure and capacitive performance of the resulting products were investigated. CaCl2·6H2O has an expansion effect on pores, resulting in reduction of micropores. Hence, the specific surface area of the resulting porous carbon increased first and then decreased with the increase of CaCl2·6H2O concentration. In addition, the erosion of NH3 and CO2 (produced by the decomposition of urea) at high temperature on the surface of the samples promoted the formation of porous structure. Urea plays the dual role of doping and activation agent. The morphology and structure analysis shown that the activated samples exhibited hierarchical pore structure, large specific surface area, and high heteroatom content. The optimal sample NAC-20 exhibited good capacitive performance, including high specific capacitance of 260.9 F g−1 at 0.1 A g−1 and good rate performance. Moreover, the symmetric supercapacitor exhibited a maximum energy density and power density of 16.2 Wh kg−1 and 19.0 kW kg−1, respectively, in 6 M KOH electrolyte. In this work, a green, low-cost molten salt activation method was proposed to synthesis biomass derived porous carbon materials for energy storage devices.

Facile and scalable synthesis of functionalized hierarchical porous polymers for efficient uranium adsorption

Efficient uranium capture from wastewater holds great importance for the environmental remediation and sustainable development of nuclear energy, but it is a tremendous challenge. Herein, a facile and scalable approach is reported to fabricate functionalized hierarchical porous polymers (PPN-3) decorated with high density of phosphate groups for uranium adsorption. The as-constructed hierarchical porous structure could allow rapid diffusion of uranyl ions, while abundant phosphate groups that serve as adsorption sites could provide the high affinity for uranyl. Consequently, PPN-3 shows a high uranium adsorption uptake of 923.06 mg g−1 and reaches adsorption equilibrium within simply 10 min in uranium-spiked aqueous solution. Moreover, PPN-3 affords selective adsorption of uranyl over multiple metal ions and possesses a rapid and high removal rate of U(VI) in real water systems. Furthermore, this study offers direct polymerization strategy for the cost-effective fabrication of phosphate-functionalized porous organic polymers, which may provide promising application potential for uranium extraction.

Simple synthesis of acyl coupling conjugated microporous polymers monolithic material for synergistic capture of PM and CO2 in flue gas and process simulation

Adsorption and separation technologies based on physical adsorbents have the advantages of simple operation, low heat of adsorption and easy regeneration. They have received much attention for the capture of CO2 and PM from flue gases. However, the inherent “trade-off” between adsorption capacity and adsorption selectivity, as well as the high gas permeation resistance after powder processing and shaping, severely limit the prospects for industrial applications. Here, acyl functional groups were strategically introduced into polymer frameworks to successfully synthesize monolithic adsorbents (AC-CMPs) with a hierarchical pore structure for PM capture and CO2/N2 selective adsorption. The three-dimensional network structure composed of aligned hollow nanotubes effectively enhances the dispersion and mass transfer of gas flow per unit volume. Based on the porous media, multiphase flow model and discrete phase model, the gas flow process of PM trapped by AC-CMPs was simulated using Fluent. The simulation dynamically revealed the relationship between permeability resistance and filtration efficiency. The highly delocalized π-π conjugated porous skeleton linked by continuous covalent bonds endowed AC-CMPs with good stability, which prevented them from degrading in humid and high-temperature environments, thus keeping the adsorption capacity unchanged. The high polarity environment generated by the open oxygen atoms within the AC-CMPs framework, along with a high micro/mesopore ratio, enable it to achieve a CO2 adsorption capacity of 2.07 mmol/g at 273 K and 1 bar. Ideal adsorption solution theory calculations (IAST) and CO2/N2 column breakthrough experiments confirmed the excellent CO2 selectivity of AC-CMPs under realistic carbon capture conditions.

Microwave construction of the 3D porous interconnected structure of NiCoCr medium-entropy alloy with ultra-high specific capacity for supercapacitors and electrocatalysis

The effective design of bifunctional electrodes with unique morphology and remarkable electrochemical properties for energy conversion and storage devices is a promising but challenging endeavor. Herein, self-supporting NiCoCr medium-entropy alloy (MEA) with a hierarchical porous network structure was in situ synthesized on nickel foam (NiCoCr/NF) by a simple and rapid microwave route. The optimal NiCoCr/NF presented an ultra-high specific capacity of 3011.8 C g−1 (1 A g−1) and outstanding charge/discharge sustainability (83.4% retention at 10 A g−1 over 50,000 cycles) due to its multi-component synergistic effect and hierarchical porous structure. Meanwhile, subtle lattice distortions and electron density redistribution in the NiCoCr MEA tuned electronic structures, resulting in a low overpotential and Tafel slope. Aqueous and solid-state asymmetric supercapacitors were fabricated by using NiCoCr/NF as a cathode and Bi/NF as an anode. The aqueous supercapacitor displayed an exceptional energy density of 314.4 Wh kg−1 at a power density of 800 W kg−1 with 81.8% retention at 10 A g−1 over 20,000 cycles. This study provides a new strategy for the efficient synthesis of electrode materials with interconnected network structures and paves the way for the broader application based on medium-entropy and high-entropy materials as promising candidates for future energy storage devices.

One-pot synthesis of interconnected carbon-coated silicon nanosheets from clay minerals for high-performance lithium-ion battery anodes

The silicon nanosheet/carbon composite emerges as a promising anode material for the next-generation commercial lithium-ion batteries. However, complex, costly, and energy-intensive synthesis procedures impede its practical application. Herein, the carbon-coated silicon nanosheets (Si/C) have been successfully synthesized via a one-pot strategy, involving a modified magnesiothermic reduction of talc followed by a reaction with CO2. The distinct chemical composition and layered nanostructure of talc enable the retention of Si nanosheets during exothermic reactions without additional templates or heat absorbents. The method shows significant potential for the scalable production of Si/C owing to the abundant silicon source, sustainable carbon source, and straightforward protocol. The resulting Si/C displays a hierarchical porous structure, with both macropores and mesopores, and an interconnected network of carbon-coated Si nanosheets. These structural characteristics facilitate rapid Li+ diffusion and enable the material to accommodate the lithiation-induced mechanical strains. As a result, the Si/C electrode exhibits outstanding electrochemical performance, including a remarkable rate capability (with a specific capacity of 1220 mAh g−1 at 10.0 A g−1) and a high initial Coulombic efficiency of 88%. The work opens a new avenue for the development of Si/C composites from natural clay minerals through an economical and scalable strategy, which would contribute to the practical application of advanced Si-based anodes in lithium-ion batteries.

Preparing conductive polymer-based adsorbent with better cupric ion adsorption efficiency by monomer precursor cross-linking method

Abstract Conductive polymer-based adsorbents have showed excellent heavy metal ion removing capabilities. Crosslinking modification is one of the feasible methods to further improve their properties. To make use of the advantages of monomer precursor method over the polymer precursor method in forming dense interpenetrating networks, and then optimizing the surface structure of materials and providing more adsorption sites, the mesoporous cross-linked poly-o-phenylenediamine (M-CR-PoPD) prepared by using the former one and used in removing Cu2+ from aqueous solution. The FTIR results showed that the monomer was successfully crosslinked and polymerized. The loosely packed target product with a hierarchical pore structure distribution was successfully formed. The maximum adsorption capacity of 105.18 mg g−1 was obtained at 25 °C after 3 h of adsorption when M-CR-PoPD prepared at the reaction time of 6 h using anhydrous ethanol as solvent and trimethylolpropane-tris(3-aziridinyl) propionate as crosslinking agent. This value reached the optimum Cu2+ removal capability of reported PoPD-based adsorbents. According to EDX, FTIR, and XPS data before and after adsorption, the possible adsorption mechanism based on the cation-π interaction and the formation of Cu–N bonds was proposed. These results could help develop more effective conductive polymer-based adsorbents to remove Cu2+ from wastewater.

Preparation of Fe-doped hypercrosslinked poly(naphthalene-based) microporous carbon and its electrochemical properties

Supercapacitors, as an eco-friendly energy storage system, have garnered significant interest due to distinct charging/discharging mechanisms, superior power density, and robust cycle stability. This study introduces a novel approach to enhance the typically low energy density of carbon materials. By employing ferrocene (Fc) as a dopant and utilizing an external crosslinker technique for “knitting”, we synthesized Fe-doped hypercrosslinked poly(naphthalene-based) polymer MON-Fe. This polymer served as a precursor for generating Fe-doped microporous carbon, termed MONC-Fe-800–1, through a chemical activation process. Comparing the structural features of MON-Fe and MONC-Fe-800–1, microporous carbon MONC-Fe-800–1 has a more pronounced hierarchical pore structure with higher microporosity (accounting for 81.43 % of its structure) and specific surface area (819.42 m2g−1). In a 6 M KOH electrolyte, the specific capacity of MONC-Fe-800–1 was observed to be 264.8 C g−1 at a current density of 1.0 A g−1, which is much higher than the specific capacity of MON-Fe (131.9 C g−1). A MONC-Fe-800–1//MONC-800–2 hybrid supercapacitor (HSC) device was constructed with an energy density of 15.2 Wh kg−1 at a power density of 750.0 W kg−1. Notably, after 5000 charge-discharge cycles at 1.0 A g−1, the device maintained 83.16 % of its initial capacity with 99.92 % coulombic efficiency, which compares with 63.87 % capacity retention and 84.00 % coulombic efficiency obtained by MON-Fe//MONC-800–2 HSC, highlighting the Fe-doped microporous carbon's enhanced electrode material potential compared to its precursor.

Highly tri-heteroatom doped porous carbon for aqueous and flexible quasi-solid-state zinc-ion hybrid supercapacitors

Porous carbon, a promising low-cost cathode material for zinc-ion hybrid supercapacitors (ZHSCs), is plagued by inferior hydrophilicity and insufficient active sites during charge/discharge process. Herein, a highly tri-heteroatom co-doped porous carbon material (HSACNS0.5) was prepared from the pyrolysis of Humulus scandens combining heteroatom doping. The high oxygen, nitrogen and sulfur content (total about 29.2 %) combining superior specific surface area (1505.9 m2 g−1) and hierarchical porous structure leads to superior wettability and abundant active sites, resulting in rapid kinetic behaviors and considerable ions adsorption capacity. Furthermore, the high content of heteroatoms provides extra pseudocapacitance. Consequently, the aqueous ZHSC based on HSACNS0.5 displays an excellent specific capacitance of 414.4 F g−1 at 0.5 A g−1, and energy density of 187.4 Wh kg−1 at a power density of 810 W kg−1. Moreover, the HSACNS0.5 cathode based flexible quasi-solid-state ZHSC operates well at different bending states. Even at a high mass loading of 17.3 mg cm−2, the ZHSC shows cycling stability and a superior areal capacitance of 4.27 F cm−2.

Nitrogen-doped porous carbon derived from cross-cutting bamboo for high-performance supercapacitors by one-pot ball milling method

In this work, Nitrogen-doped cross-cut KOH-activated porous carbon (NCKC) was obtained through a simple and effective fabrication process. Cross-cut bamboo, KOH, and urea are mixed through a one-pot ball milling strategy. The obtained sample (NCKC) has a high specific capacitance in the three-electrode test (367 F·g−1 at 0.2 A· g−1), and maintains a satisfactory specific capacitance of 183 F·g−1 at a high current of 50 A·g−1. Moreover, an aqueous supercapacitor based on NCKC with 1 M Na2SO4 as the electrolyte can provide an outstanding specific energy of 31.1 W h kg−1 with a specific power of 200 W·kg−1, without any noticeable reduction in capacity even after 40,000 cycles. This is attributed to the fact that NCKC has an abundant hierarchical pore structure. The cross-cutting process can shorten natural pores origin from bamboo native structures, and facilitate hydrophilicity in the resulting porous carbon. The results reveal that the synergistic effect of cross-cutting process, ball milling, and N-doping in carbon enhanced the electrochemical performance of carbon remarkably. The results show such one-pot ball milling method simplifies the preparation process and is of great interest for the innovation and application of high-performance electrode materials.

Hierarchical pore structure with a confined resonant mode for improving the solar energy utilizing efficiency of ultra-thin perovskite solar cells

The perovskite solar cell (PSC) has the benefits of flexibility, inexpensiveness, and high efficiency, and has important prospective applications. However, serious optical losing and low solar energy-utilizing efficiency remain a challenge for the ultra-thin PSCs because of the interface reflection of traditional planar structure. In this study, a hierarchical pore structure with a confined resonant mode is introduced and optimized by electromagnetic theory to improve the solar energy absorbing and utilizing efficiency of ultra-thin PSCs. The large pores in the top layer that support a whispering gallery mode can focus and guide the incident light into the solar cell. The small pores in the bottom layer enable backward scattering of the unabsorbed light and can improve the effective absorption of active layer. The finite-difference time-domain method is employed to optimize the geometric parameters of hierarchical pore structure to improve the light absorption of PSCs. The proposed resonant hierarchical pore structure can greatly improve sunlight absorption of ultra-thin PSCs, and the effective light absorption and photocurrent of PSCs with a hierarchical pore structure is 20.7% higher than that of PSCs with traditional planar structure. This work can offer a beneficial guideline for improving solar energy utilizing efficiency of various thin-film solar cells.

Electrochemical synthesis of hierarchical porous PbSe film and its infrared photodetection properties

Lead selenide (PbSe) has been extensively studied as an infrared detection material capable of operating at room temperature. In this research, we proposed a simple cyclic voltammetry (CV) electrodeposition of hierarchical porous PbSe on single-layer graphene film. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy were used to evaluate the physical and surface characteristics of porous PbSe films. The porous structure with large surface to volume ratio will enhance the light absorption ability after effectively sensitized in oxygen atmosphere. Furthermore, oxygen-sensitized processes create electron traps at grain boundaries, extending the lifetime of the hole carrier and improving photoconductive sensitivity. At room temperature, the porous PbSe/graphene photodetector exhibit a responsivity of 12.3 A/W, a detectivity of 5.95 * 108 cm Hz1/2W−1 (@1 kHz) at 1.55 µm, and a responsivity of 15.2 A/W, a detectivity of 1.4 * 109 cm Hz1/2W−1(@1 kHz) at 2.7 µm. This work highlights the low cost and effective electrodeposition strategy for constructing hierarchical porous structure with further application in infrared photodetection.