s a promising alternative to sluggish Li2CO3-based Li-CO2 electrochemistry, Li2C2O4 offers a favorable 2e− discharge pathway, yet its selective formation and reversible decomposition remain debated. Herein, we propose a nonmetal-metal synergistic catalyst—B-Ti coregulated layered transition metal boride Ti18B18O9/graphene (B-Ti/TiBOG)—to enable efficient CO2-to-Li2C2O4 conversion via frontier orbital engineering (FOE). Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations reveal that the low electronegativity of B (O > N > C > B) induces asymmetric Ti coordination, driving strong B 2p and Ti 3d orbital hybridization near the Fermi level, and better structural stability, outperforming C/N/O-Ti analogs. Interestingly, this unique FO alignment activates CO2 by populating its antibonding orbitals through a bidirectional “acceptance-feedback” mechanism to enhance CO2 adsorption (from −0.19 to −1.05 eV). The B-Ti synergy selectively stabilizes Li2C2O4 nucleation while kinetically suppressing its conversion to Li2CO3 (barrier > 0.68 eV). Consequently, the hybrid B-Ti/TiBOG catalyst achieves exceptional bifunctionality, yielding a minimal total overpotential (0.75 V) for CO2-to-Li2C2O4 cycling—maintained in the tetraethylene glycol dimethyl ether (TEGDME) solvent environments. This work highlights electronegativity-driven FOE in B-Ti diatomic synergy as key for rechargeable Li-CO2 batteries.
Expanding near-infrared (NIR) spectral response and utilizing ultraviolet (UV) photons are effective strategies for enhancing the power conversion efficiency (PCE) of lead halide perovskite solar cells (PSCs). However, the range of NIR spectral response extension and the utilization of UV light for devices are not enough, and the loss of photovoltaic performance caused by UV light-induced degradation is still unavoidable. Herein, we develop a novel strategy by integrating a PTB7-Th:COi8DFIC bulk heterojunction (BHJ) with perovskite layers to broaden the NIR spectral absorption range to 1050 nm. Meanwhile, the BHJ layer with a suitable energy level can effectively passivate defects, improve charge transport, and resist the erosion of moisture. The mechanism of UV light-induced degradation in PSCs demonstrates that the evolution of microstructure results in a drastic decrease in photovoltaic parameters. For increasing UV utilization, a Y2O3:Bi3+, Yb3+ film is introduced into the device to convert high-energy photons in the UV region into lower-energy photons in the visible and NIR regions by the quantum-cutting effect. After synchronously broadening the NIR spectral absorption and improving the UV spectral response of the PSCs, the efficiency is considerably improved to 23.47%, and the short-circuit current density is enhanced from 21.33 to 24.62 mA cm−2. Upgraded devices exhibit excellent UV, humidity, and long-term stability. This study explores a comprehensive strategy for obtaining high-performance and stable broad-spectral response PSCs.
The evolution of the γ′−Ni3(Al, Ti) phase in superalloys is governed by a coupled coalescence-ripening mechanism driven by elemental diffusion. In this study, thermal exposure experiments were performed at 750°C and 800°C for durations ranging from 100 to 20,000 h. The γ′ phase underwent coalescence-ripening, with its morphology evolving from small spherical particles to elliptical and finally to large spherical particles. During this process, high chemical potential gradients were observed around small-diameter γ′ phases and at the long-axis ends of elliptical γ′ phases. These gradients drove the dissolution of smaller γ′ phases by larger ones and the evolution of elliptical γ′ into spherical ones. Concurrently, the Ni/(Al + Ti) ratio in the γ′ phase decreased from 3.26 to 3.02 during exposure at 800°C. High-resolution scanning transmission electron microscopy (HR-STEM) analysis revealed complex atomic arrangements at the γ/γ′ interface and the dislocation, featuring variations in interplanar distance and abundant edge dislocations, which serve as efficient pathways for atomic diffusion. Moreover, as the γ′ phase coarsened, the γ/γ′ interfaces remained coherent, with the lattice mismatch gradually approaching zero. Geometric phase analysis (GPA) indicated a significant relaxation of elastic strain at these interfaces. Based on the change in Al concentration at the γ/γ′ interfaces, the interfacial energy decreased by approximately 3 times between 100 and 20,000 h of exposure at 800°C. This study provides foundational insights for a deeper understanding of elemental diffusion mechanisms in superalloys.
In recent years, tungsten disulfide(WS2) and tungsten selenide(WSe2) have emerged as favorable electrode materials because of their high theoretical capacity, large interlayer spacing, and high chemical activity;nevertheless, they have relatively low electronic conductivity and undergo large volume expansion during cycling, which greatly hinder them in practical applications. These drawbacks are addressed by combining a superior type of carbon material, graphene, with WS2 and WSe2 to form a WS2/WSe2@graphene nanocomposites.These materials have received considerable attention in electro-chemical energy storage applications such as lithium-ion batteries(LIBs), sodium-ion batteries(SIBs),and supercapacitors. Considering the rapidly growing research enthusiasm on this topic over the past several years, here the recent progress of WS2/WSe2@graphene nanocomposites in electrochemical energy storage applications is summarized. Furthermore, various methods for the synthesis of WS2/WSe2@graphene nanocomposites are reported and the relationships among these methods, nano/microstructures, and electrochemical performance are systematically summarized and discussed. In addition, the challenges and prospects for the future study and application of WS2/WSe2@graphene nanocomposites in electrochemical energy storage applications are proposed.
s a promising alternative to sluggish Li2CO3-based Li-CO2 electrochemistry, Li2C2O4 offers a favorable 2e− discharge pathway, yet its selective formation and reversible decomposition remain debated. Herein, we propose a nonmetal-metal synergistic catalyst—B-Ti coregulated layered transition metal boride Ti18B18O9/graphene (B-Ti/TiBOG)—to enable efficient CO2-to-Li2C2O4 conversion via frontier orbital engineering (FOE). Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations reveal that the low electronegativity of B (O > N > C > B) induces asymmetric Ti coordination, driving strong B 2p and Ti 3d orbital hybridization near the Fermi level, and better structural stability, outperforming C/N/O-Ti analogs. Interestingly, this unique FO alignment activates CO2 by populating its antibonding orbitals through a bidirectional “acceptance-feedback” mechanism to enhance CO2 adsorption (from −0.19 to −1.05 eV). The B-Ti synergy selectively stabilizes Li2C2O4 nucleation while kinetically suppressing its conversion to Li2CO3 (barrier > 0.68 eV). Consequently, the hybrid B-Ti/TiBOG catalyst achieves exceptional bifunctionality, yielding a minimal total overpotential (0.75 V) for CO2-to-Li2C2O4 cycling—maintained in the tetraethylene glycol dimethyl ether (TEGDME) solvent environments. This work highlights electronegativity-driven FOE in B-Ti diatomic synergy as key for rechargeable Li-CO2 batteries.
Expanding near-infrared (NIR) spectral response and utilizing ultraviolet (UV) photons are effective strategies for enhancing the power conversion efficiency (PCE) of lead halide perovskite solar cells (PSCs). However, the range of NIR spectral response extension and the utilization of UV light for devices are not enough, and the loss of photovoltaic performance caused by UV light-induced degradation is still unavoidable. Herein, we develop a novel strategy by integrating a PTB7-Th:COi8DFIC bulk heterojunction (BHJ) with perovskite layers to broaden the NIR spectral absorption range to 1050 nm. Meanwhile, the BHJ layer with a suitable energy level can effectively passivate defects, improve charge transport, and resist the erosion of moisture. The mechanism of UV light-induced degradation in PSCs demonstrates that the evolution of microstructure results in a drastic decrease in photovoltaic parameters. For increasing UV utilization, a Y2O3:Bi3+, Yb3+ film is introduced into the device to convert high-energy photons in the UV region into lower-energy photons in the visible and NIR regions by the quantum-cutting effect. After synchronously broadening the NIR spectral absorption and improving the UV spectral response of the PSCs, the efficiency is considerably improved to 23.47%, and the short-circuit current density is enhanced from 21.33 to 24.62 mA cm−2. Upgraded devices exhibit excellent UV, humidity, and long-term stability. This study explores a comprehensive strategy for obtaining high-performance and stable broad-spectral response PSCs.
s a promising alternative to sluggish Li2CO3-based Li-CO2 electrochemistry, Li2C2O4 offers a favorable 2e− discharge pathway, yet its selective formation and reversible decomposition remain debated. Herein, we propose a nonmetal-metal synergistic catalyst—B-Ti coregulated layered transition metal boride Ti18B18O9/graphene (B-Ti/TiBOG)—to enable efficient CO2-to-Li2C2O4 conversion via frontier orbital engineering (FOE). Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations reveal that the low electronegativity of B (O > N > C > B) induces asymmetric Ti coordination, driving strong B 2p and Ti 3d orbital hybridization near the Fermi level, and better structural stability, outperforming C/N/O-Ti analogs. Interestingly, this unique FO alignment activates CO2 by populating its antibonding orbitals through a bidirectional “acceptance-feedback” mechanism to enhance CO2 adsorption (from −0.19 to −1.05 eV). The B-Ti synergy selectively stabilizes Li2C2O4 nucleation while kinetically suppressing its conversion to Li2CO3 (barrier > 0.68 eV). Consequently, the hybrid B-Ti/TiBOG catalyst achieves exceptional bifunctionality, yielding a minimal total overpotential (0.75 V) for CO2-to-Li2C2O4 cycling—maintained in the tetraethylene glycol dimethyl ether (TEGDME) solvent environments. This work highlights electronegativity-driven FOE in B-Ti diatomic synergy as key for rechargeable Li-CO2 batteries.
Expanding near-infrared (NIR) spectral response and utilizing ultraviolet (UV) photons are effective strategies for enhancing the power conversion efficiency (PCE) of lead halide perovskite solar cells (PSCs). However, the range of NIR spectral response extension and the utilization of UV light for devices are not enough, and the loss of photovoltaic performance caused by UV light-induced degradation is still unavoidable. Herein, we develop a novel strategy by integrating a PTB7-Th:COi8DFIC bulk heterojunction (BHJ) with perovskite layers to broaden the NIR spectral absorption range to 1050 nm. Meanwhile, the BHJ layer with a suitable energy level can effectively passivate defects, improve charge transport, and resist the erosion of moisture. The mechanism of UV light-induced degradation in PSCs demonstrates that the evolution of microstructure results in a drastic decrease in photovoltaic parameters. For increasing UV utilization, a Y2O3:Bi3+, Yb3+ film is introduced into the device to convert high-energy photons in the UV region into lower-energy photons in the visible and NIR regions by the quantum-cutting effect. After synchronously broadening the NIR spectral absorption and improving the UV spectral response of the PSCs, the efficiency is considerably improved to 23.47%, and the short-circuit current density is enhanced from 21.33 to 24.62 mA cm−2. Upgraded devices exhibit excellent UV, humidity, and long-term stability. This study explores a comprehensive strategy for obtaining high-performance and stable broad-spectral response PSCs.
The evolution of the γ′−Ni3(Al, Ti) phase in superalloys is governed by a coupled coalescence-ripening mechanism driven by elemental diffusion. In this study, thermal exposure experiments were performed at 750°C and 800°C for durations ranging from 100 to 20,000 h. The γ′ phase underwent coalescence-ripening, with its morphology evolving from small spherical particles to elliptical and finally to large spherical particles. During this process, high chemical potential gradients were observed around small-diameter γ′ phases and at the long-axis ends of elliptical γ′ phases. These gradients drove the dissolution of smaller γ′ phases by larger ones and the evolution of elliptical γ′ into spherical ones. Concurrently, the Ni/(Al + Ti) ratio in the γ′ phase decreased from 3.26 to 3.02 during exposure at 800°C. High-resolution scanning transmission electron microscopy (HR-STEM) analysis revealed complex atomic arrangements at the γ/γ′ interface and the dislocation, featuring variations in interplanar distance and abundant edge dislocations, which serve as efficient pathways for atomic diffusion. Moreover, as the γ′ phase coarsened, the γ/γ′ interfaces remained coherent, with the lattice mismatch gradually approaching zero. Geometric phase analysis (GPA) indicated a significant relaxation of elastic strain at these interfaces. Based on the change in Al concentration at the γ/γ′ interfaces, the interfacial energy decreased by approximately 3 times between 100 and 20,000 h of exposure at 800°C. This study provides foundational insights for a deeper understanding of elemental diffusion mechanisms in superalloys.
