Narrow Band Gap Research Articles

Current matching and filtered spectrum analysis of wide-bandgap/narrow-bandgap perovskite/CIGS tandem solar cells: A numerical study of 34.52 % efficiency potential

Perovskite (PVK) materials with wide-bandgap (WBG) play a crucial role in achieving high-performance tandem devices but phase segregation and open-circuit voltage (VOC) loss hinders in surpassing the efficiency of single-junction solar cells. Present work discloses a numerical simulation which has been carried out using a WBG material CH3NH3PbI3-xClx of bandgap (Eg) 1.65eV as an absorber layer of the top cell (TCELL) and a Cu(In,Ga)Se2-based cell having narrow-bandgap (NBG) of Eg (1.27eV) has been used as bottom cell (BCELL). The TCELL utilizes polyethyleneimine ethoxylated (PEIE) interfacial layer to promote charge-collection and charge-tunneling. The TCELL and BCELL have been optimized by various optimization processes such as simultaneous thickness variation of active-region with defect density (DD), variation of interface defect density (IDD) with solar-cell parameters a commendable power conversion efficiency (PCE) of 27.06 %, and 26.77 % has been achieved for respective solar-devices. Variations of numerous electron transport layer (ETL) and hole transport layer (HTL) have also been performed to acquire highly optimized TCELL. Thus, a perovskite/CIGS tandem solar cell (PVK/CIGS-TSC) device has been obtained using filtered-spectra analysis and current-matching (method which display a promising photovoltaic (PV) parameter with a high VOC of 2.29 V, short-circuit current density (JSC) of 17.41 mA/cm2, fill factor (FF) of 86.45 % and PCE of 34.47 %. These discoveries hold significant promise for the future development of TSCs.

CTAB-crafted ZnO nanostructures for environmental remediation and pathogen control

This study addresses the critical need for efficient and sustainable methods to tackle organic pollutants and microbial contamination in water. The present work aim was to investigate the potential of multi-structured zinc oxide nanoparticles (ZnO NPs) for the combined photocatalytic degradation of organic pollutants and antimicrobial activity. A unique fusion of precipitation-cum-hydrothermal approaches was precisely employed to synthesize the ZnO NPs, resulting in remarkable outcomes. The synthesized CTAB/ZnO NPs demonstrated exceptional properties: they were multi-structured and crystalline with a size of 40 nm and possessed a narrow band gap energy of 2.82 eV, enhancing light absorption for photocatalysis. These nanoparticles achieved an impressive degradation efficiency of 91.75% for Reactive Blue-81 dye within 105 min under UV irradiation. Furthermore, their photocatalytic performance metrics were outstanding, including a quantum yield of 1.73 × 10–4 Φ, a kinetic reaction rate of 3.89 × 102 µmol g–1 h–1, a space–time yield of 8.64 × 10–6 molecules photon–1 mg–1, and a figure-of-merit of 1.03 × 10–9 mol L J–1 g–1 h–1. Notably, the energy consumption was low at 1.73 × 10–4 J mol–1, compared to other systems. Additionally, the ZnO NPs exhibited effective antimicrobial activity against S. aureus and P. aeruginosa. This research underscores the potential of tailored ZnO NPs as a versatile solution for addressing both organic pollution and microbial contamination in water treatment processes. The low energy consumption further enhances its attractiveness as a sustainable solution.

Synergistic Effect of Ionic Liquid and Embedded QDs on 2D Ferroelectric Perovskite Films with Narrow Phase Distribution for Self-Powered and Broad-Band Photodetectors.

2D layered metal halide perovskites (MHPs) are a potential material for fabricating self-powered photodetectors (PDs). Nevertheless, 2D MHPs produced via solution techniques frequently exhibit multiple quantum wells, leading to notable degradation in the device performance. Besides, the wide band gap in 2D perovskites limits their potential for broad-band photodetection. Integrating narrow-band gap materials with perovskite matrices is a viable strategy for broad-band PDs. In this study, the use of methylamine acetate (MAAc) as an additive in 2D perovskite precursors can effectively control the width of the quantum wells (QWs). The amount of MAAc greatly affects the phase purity. Subsequently, PbSe QDs were embedded into the 2D perovskite matrix with a broadened absorption spectrum and no negative effects on ferroelectric properties. PM6:Y6 was combined with the hybrid ferroelectric perovskite films to create a self-powered and broad-band PD with enhanced performance due to a ferro-pyro-phototronic effect, reaching a peak responsivity of 2.4 A W-1 at 940 nm.

Anchoring Ni(II) bisacetylacetonate complex into CuS immobilized MOF for enhanced removal of tinidazole and metronidazole

Here in this study, a novel ternary CuS/HKUST‒1/Ni(acac)2 nano photocatalyst (CSHK‒Ni) was developed through a facile modification of HKUST‒1 MOF with Ni(acac)2 metal complex and by immobilizing CuS into the metal-organic framework (MOF). The incorporation of CuS, a narrow bandgap semiconductor, is anticipated to allow easy excitation by visible-light and improve the photocatalytic potential of the formulated catalyst which is validated by the decrease in the bandgap energy from 3.10 eV of pristine MOF to 2.19 eV. Moreover, the anchoring of the metal complex improves the light harvesting behavior by increased conjugation. Photoluminescence studies provided evidence of the effective separation of the photoinduced charge-carriers, reducing the rate of recombination and enhancing the photocatalytic potential of the CSHK‒Ni nanocomposite. The engineered catalyst displayed remarkable efficiency in the degradation of nitroimidazole containing antibiotics, Tinidazole (TNZ) and Metronidazole (MTZ), via H2O2 assisted AOP achieving a maximum photocatalytic efficiency of 95.87 ± 1.64% and 97.95 ± 1.33% in just 30 min under irradiation of visible light at optimum reaction conditions. The possible degradation pathway was elucidated based on the identification of ROS and degradation intermediates via HR‒LCMS and quenching experiments. Meanwhile, the chemical oxygen demand (COD) and total organic carbon (TOC) removal were also examined, encompassing the discussing of various aspects including reaction conditions, influence of various oxidizing agents, competing species and dissolved organic substrates present in the wastewater, marking the novelty of the study. This research elucidated the role of the CSHK‒Ni nanocomposite as an interesting photocatalyst in the elimination of emerging nitroimidazole containing pharmaceutical pollutant under visible-light exposure, presenting an exciting novel avenue for a cleaner and greener environment in the days to come.

DFT-based simulation for the semiconductor behavior of XGeCl3 (X=K, Rb) halide perovskites under hydrostatic pressure

In this work, the structural and electronic properties of XGeCl3 (X=K, Rb) crystallized in cubic cell (Pm-3m, 221) were presented under hydrostatic pressure from 0 to 8 GPa using the first-principal Density Functional Theory (DFT) under the Perdew–Burke–Ernzerhof (PBE) form of the generalized gradient approximation (GGA). The Projector Augmented Wave (PAW) method describing electron–ion interaction was used here. For XGeCl3 (X=K, Rb), the lattice constants were calculated as 5.171 and 5.197 Å, and the band gaps were predicted as 0.5802 and 0.657 eV, respectively at ambient pressure. It was observed that the lattice parameters and bond lengths of the XGeCl3 (X=K, Rb) compounds decreased with increased pressure. The applied hydrostatic pressure reduced the band gaps, and the metallic character was detected at 5 GPa for both structures. This study provides a theoretical basis that may have potential uses in optoelectronic applications of the XGeCl3 (X=K, Rb) perovskites.

Advancements in optical and optoelectronic characteristics of benzotriazole-based asymmetric non-fullerene acceptors for organic photovoltaics

The development of energy-efficient non-fullerene acceptors (NFAs) has attracted much attention in producing efficient organic solar cells (OSCs). These innovative materials are considered a promising alternative to traditional fullerene acceptors because they absorb a broader light range and potentially enhance the OSC performance. Herein, we engineered eleven new asymmetric caterpillar-shaped materials with an A1-D-A2-A1 core as NFAs for OSCs. These efficient materials offer a high absorption efficiency, wide energy level range, and efficient charge transport capabilities. To engineer these caterpillar-shaped NFAs (FT1-FT11), we performed various synergistic modulations of end-capped electron-withdrawing moieties and side-chain engineering on the synthetic reference molecule (FT). The electron and hole reorganization energies, binding energy, transition energy, transition density analysis, electrostatic potential, and photovoltaic characterizations have been performed for these designed caterpillar-shaped (FT1–FT11) series. The designed materials (FT1–FT11) showed a lower binding energy of 0.45 eV, a narrower bandgap (2.11 eV), higher absorption (ranges from 700.44 nm to 781.05), and low electron and hole mobilities (0.0029 and 0.0031) compared to reference molecule FT. To investigate the charge transport process, we employed polymer donor PTB7-Th and efficient NFA acceptor FT11 to establish a donor:acceptor complex (FT11:PTB7-Th). The complex study demonstrates a significant charge transformation at the donor-acceptor interface. As a result, the developed compounds (FT1–FT11), with their superior optoelectronic capabilities, could be viewed as a viable and sustainable choice to fabricate next-generation efficient OSCs.

Emergence of defects-mediated diluted ferromagnetic semiconductor (ZnS: La3+) Quantum Dots: A versatile platform for optoelectronic and spintronic applications

For the first time, La3+ ions incorporated into semiconductor Zinc Sulfide-Quantum Dots (ZnS-QDs), Zn1-xLaxS, were effectively produced via a straightforward co-precipitation approach, with diverse La ratios (0.00 ≤ x ≤ 0.15 at%). The phase analysis of the acquired QDs, conducted through Raman analysis and X-ray diffractometer (XRD), revealed a singular cubic ZnS structure, devoid of any impurities. Morphology studies by HR-TEM showed a nearly spherical particle with a size of approximately 6.4 nm. X-ray photoelectron spectroscope (XPS) investigation disclosed the significant presence of sulfur vacancies, along with the existence of the trivalent oxidation state of lanthanum (La3+) within the ZnS structure. Optical absorbance studies exhibited that all QDs were positioned approximately at the absorption edges of around 270 nm (4.59 eV), surpassing the bulk ZnS energy gap of 337 nm (3.67 eV), harmonically with the quantum confinement effect. Additionally, a pronounced band gap narrowing was observed with increasing the doping level of La ions, on account of the presence of defects that result in the creation of localized states inside the ZnS band structure. The optical results indicated the capability to fine-tune the optical energy gap, dispersion parameters, and enhance the nonlinear optical parameters, which makes these QDs well-suited for use in optoelectronic devices. Furthermore, the photoluminescence (PL) spectra indicated that the La3+-doped ZnS nanocrystals (NCs) exhibited a wide visible emission band (blue emission) at room temperature, influenced by the La-doping concentration. Besides, the La3+-doped ZnS QDs elucidated ferromagnetic behavior at room temperature, which may be accredited to the vacancy-assisted bound magnetic polaron model. Exploring the intriguing magnetic features of ZnS: La3+ QDs could open avenues for developing innovative spintronic devices.

High electroresistance in all-oxide ferroelectric tunnel junctions enabled by a narrow bandgap Mott insulator electrode

Ferroelectric tunnel junctions (FTJs) based on epitaxial complex oxide heterostructures are promising building blocks for developing low power nanoelectronics and neuromorphic computing. FTJs consisting of correlated oxide electrodes have distinct advantages in size scaling but only yield moderate electroresistance (ER) at room temperature due to the challenge in imposing asymmetric interfacial screening and large modulation of the tunneling potential profile. Here, we achieve large ER in all-oxide FTJs by paring a correlated metal with a narrow bandgap Mott insulator as electrodes. We fabricate epitaxial FTJs composed of 2.8 and 4 nm PbZr0.2Ti0.8O3 tunnel barriers sandwiched between correlated oxides LaNiO3 and Sr3Ir2O7 electrodes. An ER of 6500% has been observed at room temperature, which increases to over 105% at 100 K. The high ER can be attributed to ferroelectric polarization induced metal–insulator transition in interfacial Sr3Ir2O7, which enhances the potential asymmetry for the tunnel barrier. The temperature dependence of tunneling current shows that direct tunneling dominates in the on state, while the off-state conduction transitions from thermally activated behavior at high temperatures to Glazman–Matveev defect-mediated inelastic tunneling at low temperatures. Our study provides a viable material strategy for designing all-oxide FTJs with high ER, facilitating their implementation in nonvolatile memories and energy-efficient computing devices.

Suppressed Defects by Functional Thermally Cross-Linked Fullerene for High-Efficiency Tin-Lead Perovskite Solar Cells.

Mixed tin-lead (Sn-Pb) perovskites have attracted the attention of the community due to their narrow bandgap, ideal for photovoltaic applications, especially tandem solar cells. However, the oxidation and rapid crystallization of Sn2+ and the interfacial traps hinder their development. Here, cross-linkable [6,6]-phenyl-C61-butyric styryl dendron ester (C-PCBSD) is introduced during the quenching step of perovskite thin film processing to suppress the generation of surface defects at the electron transport layer interface and improve the bulk crystallinity. The C-PCBSD has strong coordination ability with Sn2+ and Pb2+ perovskite precursors, which retards the crystallization process, suppresses the oxidation of Sn2+, and improves the perovskite bulk and surface crystallinity, yielding films with reduced nonradiative recombination and enhanced interface charge extraction. Besides, the C-PCBSD network deposited on the perovskite surface displays superior hydrophobicity and oxygen resistance. Consequently, the devices with C-PCBSD obtain PCEs of up to 23.4% and retained 97% of initial efficiency after 2000h of storage in a N2 atmosphere.

First-principles calculations to investigate optoelectronic of transition-metal half-Heusler alloys MTiSn (M = Pd and Pt) for optoelectronics applications

The structural, mechanical, optical, and electronic properties of half-Heuslers MTiSn (M = Pd and Pt) are investigated using FP-LAPW incorporating the GGA-PBE. MTiSn crystallize in ferromagnetic (FM) and cubic structure (F-43m; C1b) with lattice constants of 6.216 Å and 6.241 Å, respectively, in good agreement with the available data. Elastic constants Cij reveal that MTiSn meet the mechanical stability criteria with notable thermodynamic properties. Also, we have conducted a detailed analysis of optical properties, encompassing the dielectric function, absorption coefficient, optical conductivity, optical refractivity, and extinction coefficient. It is found that PtTiSn shows higher optical responses than PdTiSn at low and high energy ranges. In terms of electronic properties, MTiSn demonstrate narrow bandgap semiconductor characteristics with an indirect bandgap of Eg = 0.507 eV (M = Pd) and Eg = 0.782 eV (M = Pt). The notable optoelectronic responses have also been examined, indicating the high potential of MTiSn materials for optoelectronic applications.

Enhanced Phase Stability and Reduced Bandgap for CsPbI3 Perovskite through Bi3+ and Cl– Co-Doping

All-inorganic perovskite CsPbI3 is emerging as a thermally more stable alternative to organic-inorganic hybrid perovskites. However, CsPbI3 perovskite suffers from poor phase stability at ambient temperature, and its bandgap is a bit too large as light-harvesting materials in both single-junction and perovskite-on-silicon tandem solar cells. In this study, we propose an electrically neutral co-doping strategy that equimolar Bi3+ (occupying the Pb site) and Cl– (occupying the interstitial site) are incorporated into CsPbI3. Unlike the individual Bi3+ or Cl– doping, the neutral co-doping can avoid stimulating the formation of the detrimental native defects. Our first-principles calculations suggest that the co-doped systems are stable at ambient temperature and possess narrower bandgaps compared with the undoped CsPbI3. Moreover, the electron and hole states are spatially separated in these multiple-ion compounds.

Retinomorphic Color Perception Based on Opponent Process Enabled by Perovskite Bipolar Photodetectors.

The ability to perceive color by the retina can be attributed to both its trichromatic photoreceptors and the antagonistic neural wiring known as the opponent process. While neuromorphic sensors have been shown to demonstrate memory and adaptation capabilities, color perception is still challenging due to the intrinsic lack of spectral selectivity in narrow bandgap semiconductors. Furthermore, research on emulating neural wiring is severely lacking. The combination of halide perovskite materials with a tunable bandgap and a novel bipolar photodetector design emulates the efficiency of the retina in processing color information. The stimuli-responsive material is also responsible for maintaining partial color constancy-an adaptation feature. Leveraging the unique enhancement of color contrasts, an in-sensor data compression and edge detection can also be demonstrated. The color perception, chromatic adaptation, and color contrast enhancement make perovskite bipolar photodetectors a unique example where the sensor and neural wiring can be co-developed in conjunction.

Catalytic activity of Nb-doped α-Fe2O3—Heterojunction structure, ferrimagnet-like character, and high activity

Photocatalytic activity of α-Fe2O3 under visible light had been studied intensively. Rapid electron-hole recombination is the main drawback of α-Fe2O3 and the photocatalytic activity can be enhanced by transition metal doping and heterojunction structure. In the present study, α-Fe2O3 doped with various amounts of Nb were synthesized using a simple sol–gel method, and further characterization and catalytic activity were investigated. PXRD, TEM-EDS and Mössbauer measurement showed the formation of weak-ferromagnetic Nb-doped α-Fe2O3 and FeNbO4, where heterojunction structure was suggested. UV–vis spectrum showed a broad absorption in visible-light regions with a narrow band gap between 2.27 and 2.97 eV. Photo-Fenton reaction using α-Fe2O3 to decompose methylene blue (MB) was conducted to evaluate the catalytic activity. Nb-doped sample showed a significant improvement compared with pure α-Fe2O3. PXRD and Mössbauer spectroscopy revealed the α-Fe2O3 and FeNbO4 phases, which were attached to a magnet due to the ferrimagentic character of Nb-doped α-Fe2O3. The high catalytic activity with k value 7.1 * 10−2/min was obtained for 7.4Nb600. Higher catalytic activity was also observed for 20Nb600 and 40Nb600, which were driven by higher surface area, Nb substitution and heterojunction structure. Mechanistic analysis revealed that the primary reaction of MB decomposition is the Photo-Fenton process.

Bifunctional Bismuth-Based Layered Double Hydroxide Sonosensitizer for Magnetic Resonance Imaging-Guided Sonodynamic Cancer Therapy.

Novel inorganic sonosensitizers with excellent reactive oxygen species (ROS) generation activity and multifunctionality are appealing in sonodynamic therapy (SDT). Herein, amorphous bismuth (Bi)-doped CoFe-layered double hydroxide (a-CoBiFe-LDH) nanosheets are proposed via crystalline-to-amorphous phase transformation strategy as a new type of bifunctional sonosensitizer, which allows ultrasound (US) to trigger ROS generation for magnetic resonance imaging (MRI)-guided SDT. Importantly, a-CoBiFe-LDH nanosheets exhibit much higher ROS generation activity (≈6.9 times) than that of traditional TiO2 sonosensitizer under US irradiation, which can be attributed to the acid etching-induced narrow band gap, high electron (e-)/hole (h+) separation efficiency and inhibited e-/h+ recombination. In addition, the paramagnetic properties of Fe ion endow a-CoBiFe-LDH with excellent MRI contrast ability, making it a promising contrast agent for T2-weighted MRI. After modification with polyethylene glycol, a-CoBiFe-LDH nanosheets can function as a high-efficiency sonosensitizer to activate p53, MAPK, oxidative phosphorylation, and apoptosis-related signaling pathways, ultimately inducing cell apoptosis in vitro and tumor ablation in vivo under US irradiation, which shows great potential for clinical cancer treatment.

Metal oxide-combined sol-gel synthesized ceria nanoparticles: An operative photocatalyst for visible-light-driven mineralization of ciprofloxacin antibiotic in water

The superb spreading of antibiotic waste represents a vital issue related to water and soil contamination that distress the environment and humankind. Accordingly, various research projects for the eco-friendly degradation of such contaminants. Here, we envisioned the coupling of narrow bandgap (Eg) metal oxide with copolymeric-assisted sol-gel-prepared ceria nanoparticles (CeO2) for photoelimination of ciprofloxacin (CiP) as a model for antibiotic waste in water. The few tens nanometer-sized cubic CeO2 was receptive to the irradiated visible light by a combination of a few nanometer-sized AgVO3, Bi2O3, and CoTiO3 at 10.0 wt% by simple precipitation of their salt precursors. The designed nanostructures exposed mesoporous surfaces similar to the pristine CeO2 with a specific surface area range of 165–169 m2 g−1. The 1.25 mg mL−1 dose CoTiO3-composited CeO2 displayed the best-performed photomineralization of CiP (98 ± 1.2 %) within only 2 h of light illumination compared to added oxides with an outstanding reaction rate of 0.0297 min−1. In addition, the CoTiO3/CeO2 displayed a bearable recyclability of five times with 93 % of its mineralization efficiency. The boosted photoactivity of CoTiO3/CeO2 is referred to the momentous light captivation and a band alignment with Eg minimization to 2.48 eV. Also, the constructed heterojunction among n-type CoTiO3 and n-type CeO2 has improved the photoexcited charge separation and migration as resolved by high photocurrent and photoluminescence suppression. Such a comparative study proposes an efficient photocatalyst design for clean and sustainable antibiotic waste remediation.

Fabrication of a family of BiOI-doped copper-organic frameworks for enhancing photocatalytic degradation of dyes

Organic dyes are one of the most popular dyes used in industrial and consumption nowadays, and the use of dyes has certain hazards. One of the greenest and most efficient methods for breaking down organic contaminants is photocatalysis. It is a green technology that has enormous promise for the environment and energy sectors. In this work, p-type BiOI nanosheets were deposited in situ on n-type copper-based metal–organic framework (Cu-MOF) to create a unique BiOI@Cu-MOF heterojunction. The BiOI@Cu-5 heterojunction that is optimized showed nearly 100 % removal of rose Bengal (RB) under UV irradiation as well as the degradation rates of methyl orange (MO), crystal violet (GV), methylene blue (MB), and rhodamine B (RhB) were 99.70 %, 95.70 %, 27.20 %, and 23.90 %, respectively. First, the introduction of narrow bandgap BiOI into the material can effectively enhance its absorption of sunlight. Secondly, the high specific surface of the Cu-based MOFs material is favorable for improving the catalytic activity of the catalyst. More critically, the intrinsic electric field at the Cu-MOFs/BiOI heterojunction interface facilitates a successful division of photogenerated electron-hole pairs. Further studies revealed that the photogenerated holes are the important active ingredients for RB scavenging. In this paper, Bi-based semiconductors were used to create p-n heterostructures that will bring new ideas for increasing MOF photocatalytic activity.

Computational investigation of electronic, thermoelectric, and optical properties in Cs2Li[formula omitted](X = Br, I) for energy harvesting applications

The remarkable potential of double perovskite materials, characterized by lead-free, non-toxic attributes and robust dynamical stability, positions them as highly promising candidates for both thermoelectric and optoelectronic applications. In light of this, a comprehensive investigation is undertaken through density functional theory to thoroughly explore the optoelectronic and transport characteristics of Cs2LiBiX6 (X = Br, I) double perovskite materials. To ascertain dynamic stability, phonon dispersion band structures are computed, and the structural stability is evaluated through the tolerance factor. The resulting band structures reveal narrow band gaps of 3.45 eV and 1.79 eV for the Br and Indium-based DPs, respectively. These narrow band gaps hold significant importance for applications such as ultraviolet detectors and other optoelectronic devices that function in the visible and UV-light spectrum. Notably, absorption peaks of maximal intensity emerge at 5.1 eV (76 nm) and 4.0 eV (67 nm) for the Br and Indium-based double perovskites, respectively. Furthermore, a comprehensive analysis of thermoelectric behavior is conducted, encompassing the figure of merit, power factor, Seebeck coefficient, and the ratio of electrical to thermal conductivity across a temperature range of 50–800 K. The exceptionally low lattice vibration values, coupled with a substantial enhancement in the thermoelectric figure of merit (ZT), notably underscore their significance for advanced thermoelectric generator applications.

Revealing the Effect of Anion Regulation in NiCo2X4 (X = O, S, Se, Te) on Photoassisted Methanol Electrocatalytic Oxidation.

Designing nonprecious metal anode catalysts for photoassisted direct methanol fuel cells (PDMFCs) remains a challenge. As a semiconductor catalyst with a spinel structure, NiCo2O4 has good methanol catalytic oxidation activity and photocatalytic activity, making it a highly promising anode non-noble metal catalyst for PDMFCs. However, compared with the noble metal catalyst, the photoelectrocatalytic activity remained to be improved. In this report, an anion regulation strategy was adopted to improve the photoassisted methanol electrocatalytic activity. Using a CoNi-Aspartic (CoNi-Asp) nanorod as the precursor, the anion-regulated NiCo2X4 (X = O, S, Se, Te) was prepared by oxidation, sulfuration, selenization, and telluridation reactions. The regulation of anions and their effects on the electronic structure, intermediate product, and photoelectric catalytic performance of NiCo2X4 (X= O, S, Se, Te) was systematically discussed. Photoelectrochemical characterization and adsorption energy of •OH revealing the volcano-like correlation between the anion in NiCo2X4 (X = O, S, Se, Te) and their photoelectrocatalytic performance. The narrowest band gap (2.239 eV), the highest •OH adsorption energy (-3.32 eV), and the highest ratio of Co3+/Co2+ (2.19) ensure the best photoelectric catalytic performance of NiCo2S4, under the visible light irradiation, the photoresponse current density was 1.9 A g-1, the current density at 0.6 V was up to 21.9 A g-1. After 9 h of stability testing, the current retention rate was 80%. This report sheds an idea for the rational design of non-noble anode catalysts for PDMFCs.

Kesterite‐Type Narrow Bandgap Piezoelectric Catalysts for Highly Efficient Piezocatalytic Fenton System

AbstractPiezocatalytic Fenton (PF) system emerges as a promising approach to wastewater treatment by leveraging piezocatalysis to enhance Fenton‐like reactions. However, conventional piezocatalysts encounter challenges because they often compromise catalytic properties in biased favor of superior piezoelectricity, resulting in sluggish catalytic kinetics. To tackle this trade‐off, here a novel class of kesterite‐type narrow bandgap piezoelectrics, Cu2XSnS4 (CXTS, X = Zn, Ni, Co), is developed for PF reactions, which exhibit a unique combination of physicochemical attributes favorable for catalysis such as narrow bandgap (1.2–1.5 eV), high free charge density (1 × 1018 cm−3), mobility, and redox activity while retaining excellent piezoelectricity (62–142 pm V−1). With the well‐balanced piezoelectric, semiconducting, and catalytic properties, CXTS‐based PF systems demonstrate outstanding performance for tetracycline degradation, delivering a notable reaction kinetics of 0.34 min−1 only with a minor H2O2 dosage (1.2 mm), outperforming most of the conventional Fenton‐like reactions requiring a large amount H2O2 dosage by a factor up to 10. Such a remarkable performance is fulfilled by the simultaneously effective H2O2 activation and in situ generation of reactive oxygen species from oxygen and water via piezocatalysis. Additionally, the distinctive hierarchical morphology consisting of 2D nanosheets enables easy crystal domain deformation to trigger the piezoelectric effect, thereby drastically reducing the mechanical energy input required to drive redox reactions. Rigorous testing has validated the viability and practical feasibility of this system. The study offers a new design strategy for highly efficient piezocatalysts in the PF systems, enabling a cost‐effective and sustainable water treatment approach.

A p-n heterojunction PdO/CeO2 photocatalysts with enhanced photocatalytic ability for reduction of Hg(II) ions from aqueous solution

Heterostructured photocatalysts represent an essential role in the catalytic redox reactions in wastewater during illumination. In this contribution, p-n heterojunction PdO/CeO2 photocatalysts were constructed with enhanced photocatalytic ability for the reduction of Hg(II) utilizing HCOOH as hole scavengers under visible light. PdO NPs were uniformly spread on the mesoporous CeO2 surface, to act as potential separation centers of electrons and holes. The synthesized PdO/CeO2 nanocomposites exhibited an excellent photocatalytic ability, contrasted to the bare CeO2 NPs. The photocatalytic ability of PdO/CeO2 nanocomposites for reduction of Hg(II) has existed in the trends of 2%PdO ≥1.5%PdO >1%PdO >0.5 % PdO/CeO2 nanocomposites > bare CeO2 NPs. A photocatalytic ability of 100 % for Hg(II) reduction was achieved within 40 min utilizing 1.5 % PdO/CeO2 nanocomposites, which was 2.2 folds greater than that of bare CeO2 NPs. The rate constant of 1.5 % PdO/CeO2 nanocomposite (0.106 min−1) is more 9.9 times than that CeO2 NPs (0.0107 min−1). The enhancement photocatalytic ability of PdO/CeO2 can be interpreted to the wide surface area, narrow bandgap, numerous active sites, fast mobility, efficient diffusion of Hg(II), and the high separation rate of photocarriers. Considering the promotion photocatalytic ability of heterojunction PdO/CeO2 nanocomposites, the heterostructure photocatalyst is of magnificent importance to the photocatalytic redox reactions and exhibits a significant effect on our human health and ecological environment.