2D Janus Research Articles

The Defects Genome of Janus Transition Metal Dichalcogenides.

2D Janus Transition Metal Dichalcogenides (TMDs) have attracted much interest due to their exciting quantum properties arising from their unique two-faced structure, broken-mirror symmetry, and consequent colossal polarization field within the monolayer. While efforts are made to achieve high-quality Janus monolayers, the existing methods rely on highly energetic processes that introduce unwanted grain-boundary and point defects with still unexplored effects on the material's structural and excitonic properties Through high-resolution scanning transmission electron microscopy (HRSTEM), density functional theory (DFT), and optical spectroscopy measurements; this work introduces the most encountered and energetically stable point defects. It establishes their impact on the material's optical properties. HRSTEM studies show that the most energetically stable point defects are single (VS and VSe) and double chalcogen vacancy (VS -VSe), interstitial defects (Mi), and metal impurities (MW) and establish their structural characteristics. DFT further establishes their formation energies and related localized bands within the forbidden band. Cryogenic excitonic studies on h-BN-encapsulated Janus monolayers offer a clear correlation between these structural defects and observed emission features, which closely align with the results of the theory. The overall results introduce the defect genome of Janus TMDs as an essential guideline for assessing their structural quality and device properties.

2D Janus Polarization Functioned by Mechanical Force.

2Dpolarization materials have emerged as promising candidates for meeting the demands of device miniaturization, attributed to their unique electronic configurations and transport characteristics. Although the existing inherent and sliding mechanisms are increasingly investigated in recent years, strategies for inducing 2D polarization with innovative mechanisms remain rare. This study introduces a novel 2D Janus state by modulating the puckered structure. Combining scanning probe microscopy, transmission electron microscopy, and density functional theory calculations, this work realizes force-triggered out-of-plane and in-plane dipoles with distorted smaller warping in GeSe. The Janus state is preserved after removing the external mechanical perturbation, which could be switched by modulating the sliding direction. This work offers a versatile method to break the space inversion symmetry in a 2D system to trigger polarization in the atomic scale, which may open an innovative insight into configuring novel 2D polarization materials.

Superconductivity in monolayer Janus titanium-sulfur hydride (TiSH) at ambient pressure

Janus two dimensional (2D) materials are new and novel materials. As they break out-of-plane symmetry, they possess several fascinating properties which can be applied in catalytic reactions and opto-electronics. Recent synthesis of MoSH and the prediction of phonon-mediated superconductivity have opened a new way to investigate the properties of hydrogenated Janus materials (Novoselov et al 2004 Science 306 666–9; Mehta et al 2023 Solid State Commun. 375 115347; Naik et al 2023 Comput. Theor. Chem. 1228 114278). In this work, we performed the density functional theory calculations to demonstrate that titanium sulfur hydride (TiSH) is dynamically stable and becomes phonon-mediated superconductor with the superconducting critical temperature, Tc = 9.24 K with the corresponding value of electron–phonon coupling constant, λ = 0.71, in the weak interaction limits, under ambient conditions. Eliashberg spectral function α2F(ω) was well converged for dense grid of q1 × q2 × q3 = 12 × 12 × 1 and nk1 × nk2 × nk3 = 140 × 140 × 1. The effect of smearing broadening was also considered for determining well converged value of Tc and λ. Figure (b) shows that after smearing broadening of 0.02 Ry, λ shows convergent values, and subsequent changes are as low as less that 5% of the peak value. Overall, our findings predicted a new member in the 2D Janus hydride family with possible applications in 2D nanomaterials and superconducting devices applications.

Prediction of a new 2D Janus monolayer MX2Si2Y2 (M = Mo, W and V; X/Y = N, P; X ≠ Y) from density functional theory

We devised the Janus monolayer MX2A2Y2 (M = Mo, W, V, Nb, Ta, Ti, Zr, Hf and Cr; X/Y = N, P and As; A = Si and Ge) and systematically investigated the structural parameters, phonon vibrations, thermal stability, the electronic and mechanical properties. Among the 26 systems, there are six stable Janus monolayers at room temperature: MoN2Si2P2, WN2Si2P2, VN2Si2P2, MoP2Si2N2, WP2Si2N2, CrN2Si2P2. Intriguingly, the MoP2Si2N2 and WP2Si2N2 show non-magnetic semiconductor properties. The MoN2Si2P2 and WN2Si2P2 demonstrate non-magnetic metallic ground states. The VN2Si2P2 and CrN2Si2P2 are magnetic metal with magnetic moments of 1.24 μB and 0.53 μB. Furthermore, the elastic constants of the MSi2N4 and five Janus monolayer MX2Si2Y2 (M = Mo, W and V; X/Y = N, P) meet the stability criteria, indicating they are mechanically stable. The in-plane stiffness of the MX2Si2Y2 increases with the increase of the number of metal atoms and are greatly reduced, compared with the corresponding MSi2N4. In addition, according to Poisson's ratio, the MN2Si2P2 with metallic characteristics are ductile, whereas the MP2Si2N2 with semiconductor characteristic are brittle. In short, the Janus monolayer MX2Si2Y2 enriches the family members of 2D materials. The rich electronic and mechanical properties make the MX2Si2Y2 have high application prospects for future novel mechanical electronic device applications.

Harnessing intrinsic electric fields in 2D Janus MoOX (X=S, Se, and Te) monolayers for enhanced photocatalytic hydrogen evolution

Two-dimensional (2D) Janus monolayers, distinguished by their intrinsic vertical electric fields, emerge as highly efficient and eco-friendly materials for advancing the field of hydrogen evolution reactions (HER). In this study, we explore, for the first time, the potential viability of the oxygenation phase of two-dimensional Janus transition metal dichalcogenides MoOX (X = S, Se, and Te) monolayers as an exceptionally efficient photocatalyst for hydrogen production. Based on first-principles computations, we demonstrate that all three monolayers exhibit semiconductor behavior, characterized by a band gap ranging from 0.66 to 1.55 eV. This narrow band gap renders the proposed materials highly efficient at absorbing light within the visible region. Excitingly, the introduction of an electrostatic potential difference ΔΦ has granted us the ability to surpass the conventional bandgap limit (Eg≥1.23). Consequently, all monolayers exhibit favorable band alignment with respect to the vacuum level. Moreover, the calculated solar-to-hydrogen efficiency for the envisaged monolayer exceeds the established theoretical limit. Particularly, the MoOTe monolayer emerges as an infrared-light-driven photocatalyst, demonstrating a remarkable solar-to-hydrogen efficiency limit of up to 25,21% when considering the entire solar spectrum. A thorough examination of the Gibbs free energy differences across these monolayers has revealed that the values during the oxygenation phase are significantly smaller and approach the optimum, in contrast to the parental two-dimensional Janus transition metal dichalcogenides. Our results conclusively establish that the proposed materials exhibit exceptional efficiency as photocatalysts for hydrogen evolution reactions. Notably, their efficacy is demonstrated even in the lack of co-catalysts or sacrificial agents.

2D Janus ZrSSe/SnSSe Heterostructure: A Promising Candidate for Photocatalytic Water Splitting.

The distinctive physical characteristics and wide range of potential applications in optoelectronic and photovoltaic devices have ignited significant interest in two-dimensional materials. Intensive research attention has been focused on Janus transition metal dichalcogenides due to their unique properties resulting from symmetry disruption and their potential in photocatalysis applications. Motivated by the current fascination with Janus TMD heterostructures, we conducted first-principles calculations to examine the stability, electronic, and optical properties of monolayers consisting of ZrSSe, SnSSe, and the ZrSSe/SnSSe heterostructure. The results indicate that the Janus ZrSSe/SnSSe heterostructure exhibits a structural and mechanical stability. Using the HSE06 functional, the ZrSSe/SnSSe heterostructure shows an indirect band gap of 1.20 eV, and band edge analysis reveals a type-II band alignment. The potential for photo/electrocatalysis in the ZrSSe/SnSSe heterostructure for water splitting or generating reactive oxygen species (ROS) has been explored, and it was found that the oxygen evolution reaction (OER) can spontaneously activate in acidic (pH = 0) media under light irradiation, with a potential of U = 1.82 eV. Additionally, the ZrSSe/SnSSe heterostructure exhibits strong light absorption across a wide range, from visible light to the ultraviolet region, at various levels. These findings open up possibilities for the application of ZrSSe/SnSSe-based materials in optoelectronic devices.

Electronic and optical properties of two-dimensional Janus Sn0.5Ge0.5S monolayer

Janus two-dimensional (2D) materials have received widespread attention in recent years due to their out-of-plane asymmetric structures which makes them promising candidates for sustainable energy devices. In this work, using first-principles calculations, we study a novel 2D Janus monolayer Sn0.5Ge0.5S for recently synthesized SnS monolayer. We investigate structural, electronic and optical properties of this new 2D Janus material. Our results show that monolayer Sn0.5Ge0.5S is an indirect band gap semiconductor with the lowest conduction band is nearly flat around the band minimum. Atom projected band structure reveals that this flattened valley is mainly originated from orbitals of Sn atom. In addition, the inclusion of spin–orbit coupling leads to splitting of the bands, largely along Γ-Y direction. Optical absorption spectra indicate superior sunlight absorption in the visible and ultraviolet regions. Interestingly, absorption spectra of Janus monolayer Sn0.5Ge0.5S are polarization dependent owing to its anisotropic crystal structure along zigzag and armchair directions.

Piezoelectric response and ferromagnetic order in 2D Janus FeGeN3

Two-dimensional (2D) materials with ferromagnetism and piezoelectricity have drawn great attention due to their promising application and fundamental significance. Using first-principles swarm structure search calculations, we have predicted a 2D Janus FeGeN3, with quintet atomic layers of N–Fe–N–Ge–N, demonstrating a desirable coexistence of ferromagnetism and piezoelectricity. It has an out-of-plane piezoelectric response of −0.31 pm/V, a robust ferromagnetic order with a Curie temperature (TC) of 302 K, and an excellent semiconductivity with a bandgap of 1.99 eV. Its ferromagnetic coupling is derived from the super-exchange interaction between Fe atoms mediated by multi-type N atoms. Moreover, the biaxial tensile strain is in the favor of the enhancement of ferromagnetism. These intriguing properties make Janus FeGeN3 an attractive candidate for spintronic devices with multifunctionality.

Computational investigation on 2D Janus MSiGeN4 with structural, electronic properties, quantum capacitance, and photocatalytic activity

Inspired by the superior properties of Janus MA2Z4, the electronic properties, quantum capacitance, and photocatalytic activity of Janus MSiGeN4 (M=Cr, Hf, Mo, Nb, Ta, Ti, V, W, and Zr) monolayers are explored. The results indicate that TiSiGeN4, ZrSiGeN4, and HfSiGeN4 are semiconductors with the bandgap larger than 2 eV. NbSiGeN4 is a spin-polarization semiconductor with magnetic moment of 0.61 μB. VSiGeN4 exhibits the character of half-metal and its spin-up channel hosts a Dirac cone around Fermi level, which is derived from V-d states. The analysis of Bader charge shows that built-in electric field in these systems appears and promotes the charge redistribution across the Janus atomic layer. All systems except NbSiGeN4 and TaSiGeN4 are cathode materials because of |Qp|/|Qn| larger than 1 in aqueous system. Broad voltage keeps the electrode type of all systems unchangeable. MSiGeN4 (M=Hf, Nb, Zr, V, Ti) can perform photocatalytic water splitting, while all MSiGeN4 can reduce N2 to NH3, but are not good CO2 photocatalysts. The Bader charge, work function, and optical properties are further explored.

Two-dimensional 1T′ α -VXY (X = S, Se, Te; Y = Cl, Br, I): A multifunctional vanadium chalcohalide family with room-temperature ferromagnetism and sliding ferroelectricity

Two-dimensional (2D) ferromagnetic materials with Curie temperature (Tc) above room temperature have great potential ranging from spintronics to information processing and storage. Here, we computationally design a series of 1T′α-VXY (X = S, Se, Te; Y = Cl, Br, I) monolayers with the X and Y atoms arranged alternately in the 2D plane. VXY monolayers are ferromagnetic semiconductors with Tc much higher than room temperature. Furthermore, the symmetry breaking of VXY bilayers leads to sliding ferroelectricity with large reversible out-of-plane electric polarization and moderate interlayer sliding barriers. We further show that half-metal-to-semiconductor nonvolatile field-effect switching can be achieved in multiferroic van der Waals heterostructures composed of VXY and In2S3 ferroelectric substrates due to the synergistic effect between the polarization field-induced band edge shifting and the selective charge transfer at the interface. These findings reveal a promising role of 2D Janus 1T′α-VXY in spintronics, ferroelectric, and multiferroic device applications.

A new 2D Janus family with multiple properties: auxetic behavior, straintunable photocatalyst, high Curie temperature ferromagnets, and piezoelectric quantum anomalous Hall insulator

A new 2D Janus family with multiple properties: auxetic behavior, straintunable photocatalyst, high Curie temperature ferromagnets, and piezoelectric quantum anomalous Hall insulator

An Efficient Descriptor for Rapid Determination of Dipole Moments and Band Alignments of 2D Janus Transition‐Metal Dichalcogenides

AbstractThe dipole moment (µ) is a critical parameter in Janus structures, influencing band alignments and carrier transmissions. However, evaluating µ in 2D Janus layers is challenging due to the vast number of structures and the inefficiency of Kelvin probe force microscopy. Using the recently developed 2D Janus transition‐metal dichalcogenides (TMDCs) as a prototype, a descriptor is proposed based on fundamental parameters (atomic number and atomic radii) to investigate the relationship between atomic structures and µ. By constructing 621 structural models, this descriptor is applicable from monolayers to three‐layers. By considering shielding effect of terminal atoms, the performance of the descriptor has been significantly enhanced, resulting in a description accuracy of 94.6% for all TMDC systems. Based on this descriptor, the Anderson's Rule (AR) model can be extended to Janus bilayers in simulating band alignments, resulting in a substantial improvement in accuracy from 20.0% to 90.8%. This development holds crucial importance in screening Janus self‐doping P‐N junctions. The work provides an efficient descriptor based on inherent atomic properties for rapid determining dipole moment and band alignment in 2D Janus TMDCs, accelerating the design of devices with built‐in electronic field structures.

Free‐Standing Janus Nanosheets: Ultrafast Self‐Assembly and Versatile Biphase‐Application

AbstractThe development of stable Janus architectures suitable for biphasic applications holds significant importance. A novel approach is introduced for interfacial supramolecular self‐assembly, resulting in 2D Janus nanosheets (OA‐TA/Fe) exhibiting an amphiphilic nature. These nanosheets consist of hydrophilic coordination complexes of ferric ions (Fe3+) and tannic acid (TA) on one side of both surfaces and hydrophobic alkyl chains on the other side of both surfaces. The synthesis of these 2D Janus nanosheets involves a simple, ultrafast, and environmentally benign process, eliminating the need for time‐consuming multistep procedures and harsh synthetic conditions typically associated with Janus architecture formation. By exploiting the inherent singular anisotropic wettability inherent in OA‐TA/Fe‐2, the efficacy of these innovative Janus nanosheets in the efficient separation of various organic liquid‐in‐water and water‐in‐organic liquid emulsions is elucidated. Subsequent post‐modification of OA‐TA/Fe has facilitated the highly efficient remediation of contaminated oily wastewater, serving as a model biphasic catalysis reaction, wherein the Janus nanosheets function simultaneously as emulsifiers and catalysts within biphasic mixtures. The methodology establishes a rapid self‐assembly approach for the creation of amphiphilic free‐standing Janus nanosheets, offering compelling prospects for their application in diverse fields, as exemplified by, but not limited to, the case studies presented herein.

Janus MSiSnN4(M= Mo; W):High efficiently overall water splitting photocatalyst triggered by the intrinsic electric field

Photocatalytic hydrolysis is one of the most effective ways for hydrogen fuel as a strategy for turning solar energy into hydrogen fuel. Two-dimensional(2D) Janus materials with an out-of-plane polarized electric field not only help to promote photogenerated carrier separation and migration but also alter the alignment of water splitting potentials, which enhances photo-oxidation and retains efficient absorption of visible light. In this manuscript, a systematic first-principles analysis was conducted on the WSn2N4 and MSiSnN4 (M= Mo; W) system. The results show that Janus MSiSnN4 (M= Mo; W) systems have a suitable bandgap and band edge position (span the redox position of water), as well as the ample electron mobility(>200 cm2V−1s−1) and outstanding visible light optical absorption capacity(η’STH = 23.12 % for WSiSnN4; η’STH = 32.91 % for MoSiSnN4). The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) Gibbs free energy changes of WSiSnN4 show that it can make HER and OER processes occur spontaneously under light in acidic and neutral solutions, demonstrating excellent photocatalytic performance.

Chiral breathing-valley locking in two-dimensional kagome lattice Ta3I8

The exploration of valley-related physics is essential to the development and refinement of valleytronics. Here, a paradigm called chiral breathing-valley locking (CBVL) is proposed, in which two chiral “breathing” phases are completely locked to their valley indexes. Utilizing first-principles calculations, a two-dimensional (2D) kagome lattice with large spontaneous valley polarization (VP), namely, monolayer Ta3I8, is proposed to realize CBVL. There are two breathing phases with chiral symmetry in Ta3I8, and they can change to each other under some conditions. The valley indexes change between “−K” and “K” along the breathing of the two chiral symmetric phases, so CBVL can be obtained. Remarkably, the VP is up to 199.7 meV, so CBVL can cause the obvious switching of the anomalous valley Hall effect (AVHE). Additionally, a 2D Janus Kagome structure TaI4X4 is constructed to confirm experimentally the feasibility of electric field modulation on the CBVL. The built-in electric field and the breathing mode can mutually influence each other in TaI4X4, which provides a synergistic regulation of the AVHE. Our findings broaden the horizon for exploring AVHE materials and provide a platform for future valleytronic applications.

Two-Dimensional Room-Temperature Magnetism in Janus Mn2I3S3 and Cr2I3Se3 Monolayers with Tunable Magnetic Properties by Strain Engineering.

Exploring room-temperature intrinsic magnetism in two-dimensional (2D) materials for nanoscale spintronic devices has garnered significant interest. Achieving a high Curie temperature and substantial spin polarization in 2D ferromagnetic materials remains challenging. Drawing inspiration from the substantial enhancement of the Curie temperature observed in ferromagnetic CrIS monolayers by manipulating the covalent nature of Cr-S bonds, our study systematically delves into the electronic structure and magnetic properties of Janus M2X3Y3 (M = V, Cr, Mn, Fe, and Co; X = Cl, Br, I; Y = S, Se, and Te) monolayers through first-principles calculations. Our findings reveal that 15 kinds of these monolayers exhibit dynamic and thermodynamic stability while displaying diverse electronic and ferromagnetic characteristics. Notably, Mn2I3S3 demonstrates half-metallicity and in-plane magnetic anisotropy, while Cr2I3Se3 exhibits a half-semiconductor and perpendicular magnetic anisotropy. Consequently, Mn2I3S3 transforms from in-plane to perpendicular magnetic anisotropy through strain manipulation. Cr2I3Se3, under strain, transforms from a half-semiconductor to a bipolar magnetic semiconductor. The strong coupling caused by the M-Y bonds makes them have a Curie temperature higher than room temperature. The unique magnetic properties exhibited by the 2D Janus Mn2I3S3 and Cr2I3Se3 magnets hold promise for applications in spintronics. Our study provides a foundational understanding for future experimental explorations in this exciting research area.

Study on the piezoelectric properties and the mechanism of strain-regulated piezoelectricity in flexible Janus monolayers Cr2X3Y3 (X/Y = Cl, Br, I)

Piezoelectric materials hold significant promise in piezoelectric electronics and piezoelectric optoelectronics. As a new member of this family, the 2D Janus structures characterized by central symmetry breaking have attracted much attention due to the out-of-plane piezoelectric effects. In this work, the mechanical, piezoelectric properties, and the strain regulation mechanism of Juans structure material (Cr2X3Y3, X/Y = Cl, Br, I) are systematically investigated by the first-principles methods. The calculated mechanical properties show that Cr2X3Y3 with a lower Young’s modulus of 27.31∼29.76 N m−1 is more sensitive to applied stresses, theoretically exhibiting exceptional piezoelectric properties. The in-plane piezoelectric coefficients d 11 for Cr2Br3Cl3, Cr2I3Cl3, and Cr2I3Br3 are 4.92, 9.89, and 7.86 pm V−1, respectively; the out-of-plane piezoelectric coefficients d 31 are 1.13, 2.33, and 1.64 pm V−1, respectively. Cr2I3Cl3 has the highest values of d 11 and d 31 due to the large electronegativity difference between iodine and chlorine atoms. Based on the analysis, it can be deduced that Cr2X3Y3 demonstrates substantial piezoelectric responses in both in- and out-of-plane, with potential strain regulation effects. The d 31 values of Cr2I3Cl3 show an approximately linear relationship to strain in the range from −2% to 4% and remain consistently above 2.10 pm V−1 across a broader range of strain from −4% to 6%, underscoring its robustness to strain. Our study indicates that two-dimensional Janus Cr2X3Y3 monolayers would emerge as promising candidates for diverse applications in multifunctional electronic devices.

Adjusting Electronic Properties of Janus SHfAZ2 (A═Si,Ge; Z═N, P, As) via Strain Engineering and an Electric Field

AbstractIn this work, novel monolayers of 2D Janus SHfAZ2 (A═Si, Ge; Z═N, P, As) materials are introduced. These Janus structures are primarily investigated for their ability to exhibit adjustable electronic properties when subjected to biaxial strain and an applied electric field. At equilibrium, the four structures in the Janus SHfAZ2 monolayers all display indirect bandgap semiconductor properties, with the exception of the SHfGeN2 monolayer, which exhibits direct bandgap semiconductor properties. Under the influence of biaxial strain, the study observes that the electronic properties of all SHfAZ2 monolayers can be adjusted, transitioning from semiconductor to metallic properties when subjected to compressive strain. However, the SHfSiP2, SHfGeP2, and SHfGeAs2 monolayers show limited sensitivity to an applied electric field, with their electronic properties being modifiable solely under the influence of applied biaxial strain. In contrast, both the SHfSiAs2 and SHfGeN2 monolayers demonstrate the ability to modulate their electronic properties from semiconductors to metals when subjected to both biaxial strain and an applied electric field. Finally, the carrier mobility of these five structures is calculated. The outcomes of the research provide a solid theoretical foundation for the potential utilization of 2D Janus SHfAZ2 monolayers in electronic devices.

2D Janus piezoelectric iridium trihalide Ir2X3Y3 with potential application in photocatalysts for water splitting

The Janus 2D iridium trihalide, Ir2X3Y3 (X, Y = Cl, Br, I and X ≠ Y), has been studied using first-principles calculations. We have shown that all monolayers are stable in energy, thermodynamics, dynamics and mechanics. Electronic calculations based on hybrid functional spin–orbit coupling (SOC) show that they are semiconductors with indirect band gaps ranging from 1.833 to 2.192 eV, and the band edge positions lie between the reduction potential of H+/H2 and the oxidation potential of O2/H2O. BSE calculations show that they have significant optical absorption capability in both the visible and ultraviolet light regions. The high surface area, suitable band gap, suitable band alignment and high optical absorption make them potentially applicable in photocatalytic full water splitting. The broken inversion symmetry generates a built-in electronic field along the z-direction and a significant out-of-plane piezoelectric response with piezoelectric coefficients of d31 ranging from 0.566 to 0.820 pm/V (e31 varying from 39.7 to 85.0 pC/m). The applied field accelerates charge separation and migration, thereby improving their photocatalytic efficiency. Our results would be instructive for synthesis and potential applications in photocatalytic water splitting and electromechanical devices.

Rational design of 2D Janus P3m1 M2N3 (M = Cu, Zr, and Hf) and their surface-functionalized derivatives: ferromagnetic, piezoelectric, and photocatalytic properties.

In this study, first-principles calculations were employed to rationally design two-dimensional (2D) Janus transition metal nitrides of P3m1 M2N3 phases, where M is a d-block element (Sc-Zn, Y-Cd, Hf-Hg). Among the 29 examined 2D M2N3, three 2D phases, namely P3m1 Cu2N3, Zr2N3, and Hf2N3, exhibit excellent thermodynamic, dynamic, mechanical, and thermal stabilities. These novel Janus 2D materials exhibit ferromagnetic metallic and half-metallic behavior. The related 2D Janus surface-functionalized derivatives, Cu2N3H, Cu2N3F, Cu2N3Cl, Zr2N3H, Hf2N3H, and Hf2N3F, are all dynamically stable. The 2D Janus P3m1 phases of Zr2N3H, Hf2N3H, and Hf2N3F, all with M in the +IV oxidation state, act as semiconductors in the visible region, with energy band gaps of 2.26-2.70 eV at the HSE06 level of theory. On the other hand, the 2D Janus P3m1 Cu2N3X phases (where X = H, F, and Cl) are ferromagnetic half-metals. Additionally, it has been unveiled that there are high hole mobilities (∼6 × 103 cm2 V-1 s-1) derived from the moderate deformation potential and effective mass in the 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases. Uniaxial strain engineering has demonstrated the outstanding in-plane piezoelectric properties of 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F with high d11 values (∼99.91 pm V-1). Furthermore, the desirable band-edge alignments and high anisotropic carrier mobilities of 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases indicate their potential as visible light-driven photocatalysts for water splitting reactions on different facets. These properties render 2D Janus P3m1 Zr2N3H, Hf2N3H, and Hf2N3F phases promising for use in optoelectronics, piezoelectric sensing, and photocatalysis applications.