Guo Chen

High‐entropy oxides (HEOs) with photothermal conversion capability provide a promising platform for enhancing the oxygen evolution reaction (OER) in electrocatalytic water splitting. In this work, the adsorbate evolution mechanism (AEM), the lattice oxygen mechanism (LOM), and photothermal effects are integrated into a single reaction system through Fe doping into HEOs. By combining theoretical calculations and experimental characterizations, we reveal that Fe doping optimally tailors the adsorption/desorption energetics of intermediates along the AEM, while simultaneously introducing oxygen vacancies that modulate the metal‐oxygen electronic environment and promote LOM participation. This dual‐pathway activation, enabled by the high‐entropy rock‐salt structure, enhances catalytic activity. In addition, the photothermal effect of (FeMgCoNiCuZn)O _1−x can accelerate interfacial charge‐transfer kinetics and facilitate OOH ^* deprotonation. Under Xe‐lamp irradiation, Fe doping lowers the apparent activation energy for OER from 15.3 to 11.2 kJ mol ⁻¹ , and the catalyst achieves oxygen evolution current densities of 10 and 50 mA cm ⁻² at overpotentials of 159 and 247 mV. More importantly, it exhibits outstanding long‐term durability, maintaining stable operation for over 1500 h at 1 A cm ⁻² . These findings underscore the potential of Fe‐doping hexanary HEOs as a highly efficient candidate for electrocatalytic water splitting.

Interface engineering is a useful way to fabricate nonprecious-based electrocatalyst materials for easy overall water splitting (OWS), which is of great importance for renewable hydrogen energy production. Herein, we designed a needle-like catalyst by a low-temperature CVD method using NiCu alloy nanoparticles evenly embedded in the graphene shell, resulting in a large-scale NiCu/C/NiCu interface. The few-layer graphene prevents the NiCu alloy nanoparticles from melting and growing and increases the number of interfaces. Meanwhile, the C layer coated on the surface of the NiCu alloy hinders the erosion of Cl– to the catalyst, showing excellent stability in the overall water splitting. The HER and OER overpotentials of the needle-like catalyst in a 1 M KOH solution were 53.8 and 298.5 mV (10 mA cm–2), respectively, and the HER and OER overpotentials in a 1 M KOH+0.5 M NaCl solution were 38.4 and 304.1 mV (10 mA cm–2), respectively. Assembled with two electrodes in a cell for saline water splitting, it reaches the current density of 100 mA cm–2 at an operating voltage of 1.86 V. Additionally, it also shows superb stability for 65 h at a high current density.

In this work, two types of nitrogen- and phosphorus-co-doped carbon dots (N,P1-CDs, N,P2-CDs) were successfully prepared via a solvothermal method at 180 °C for 6 h, employing o-phenylenediamine and phosphoric acid, as well as 2-aminoterephthalic acid and phosphoric acid, as the respective precursors. Characterizations including X-ray diffractometer, transmission electron microscope, X-ray photoelectron spectrometer, FT-IR, and zeta potential verify the successful co-doping of nitrogen and phosphorus. The zeta potentials of N,P1-CDs and N,P2-CDs are 8.04 mV and 7.12 mV, with corresponding fluorescence quantum yields of 11.38 and 13.2%, respectively. Both CDs exhibit outstanding pH tolerance and long-term fluorescence storage stability. As fluorescent probes, their sensing performance toward Cr6+, tetracycline (TC), and ethylene glycol (EG) was systematically investigated. Both CDs realize quantitative detection of Cr6+ within the concentration range of 5–140 μg/mL with distinct recognition selectivity: N,P2-CDs display superior performance for TC detection, while N,P1-CDs can specifically recognize EG. All sensing systems exhibit favorable linearity and relatively low limits of detection (LOD), among which the LOD of N,P1-CDs toward EG reaches only 0.1052 μM. Coexisting ion experiments prove the favorable anti-interference capacity of the two probes, and N,P2-CDs possess better stability. Satisfactory detection results are achieved in spiked real water matrices including tap water and river water, where the fluorescence quenching efficiencies for Cr6+ all exceed 93%. Mechanism analysis reveals that the detection of Cr6+ by N,P-CDs follows the photoinduced electron transfer pathway. The fluorescence quenching triggered by EG and TC originates from the synergistic effect of hydrogen bonds and inner-filter effect. The dual CDs system enables simultaneous multitarget detection of heavy metals, antibiotics, and organic solvents, which broadens the application prospects of carbon-based fluorescent materials in environmental pollutant monitoring.

To address the key issues of traditional carbon quantum dots (CQDs), such as unstable photophysical and photochemical properties and limited carrier transport performance, N,P-CQDs were prepared via a one-step hydrothermal synthesis method in this study. By regulating the mass ratio of carbon-to-nitrogen sources, we systematically explored the fluorescence properties of four N,P-CQDs. The findings demonstrated that N,P-CQDs-2 prepared at 180 °C for 8 h with a citric acid-to-ammonium dihydrogen phosphate molar ratio of 1.15:1.0 exhibited the optimal optical performance. The material showed excellent stability with 76.96% fluorescence retention after 180 days of storage at room temperature and stable fluorescence in pH 1-13, demonstrating favorable acid-base resistance. Structure, morphology, and optical properties were characterized by X-ray powder diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), transmission electron microscope (TEM), fluorescence spectrophotometer (PL), ultraviolet-visible (UV-vis), and steady-state/transient fluorescence spectrometer (FLS). All samples emitted blue fluorescence under UV light. The carbon-nitrogen ratio did not change the core structure but obviously affected fluorescence intensity and emission peaks. N,P-CQDs-2 was used as a fluorescent probe for ion detection. After different metal ions (Ni²⁺, Fe²⁺, Cu²⁺, Mg²⁺, Cr³⁺) were added to its aqueous solution, the system's fluorescence emission intensity showed differential attenuation. Among them, the fluorescence quenching effect induced by Cr³⁺ was the most significant. The fluorescence quenching efficiency of N,P-CQDs-2 shows a good linear relationship with the concentration of Cr³⁺ in the range of 150-330 μg/mL, with a correlation coefficient R² of 0.977 and a limit of detection as low as 0.25 mg/L. Based on the characterization results of FT-IR, UV-vis absorption, and fluorescence lifetime, the fluorescence quenching process is verified to be dominated by the static quenching mechanism. This green and low-cost method provides a valuable reference for efficient Cr³⁺ detection.

In response to the increasingly severe issue of heavy metal pollution in water, this paper proposes a method for the robust quantitative analysis of copper ions in purified water and real water samples based on the feature-level fusion of ultraviolet-visible absorption (UV-Vis) spectra and fluorescence spectra, combined with the Extreme Gradient Boosting (XGBoost) algorithm. Specifically, this study introduces a feature-level fusion strategy to overcome the limitations of single-spectrum detection, while the optimized XGBoost algorithm is employed to model the complex non-linear relationships that are difficult to capture using traditional linear regression methods. An optimization algorithm is introduced to fine-tune the model’s hyperparameters, thereby enhancing its predictive performance. Using the coefficient of determination (R²) and root mean square error (RMSE) as evaluation metrics, rapid and accurate detection of copper ions in water is achieved. Experimental results show that, for standard solutions, the optimized XGBoost model achieves a coefficient of determination of 0.9915 and a root mean square error of 2.6663 mg/L; for actual water samples, the optimized XGBoost model achieved a coefficient of determination of 0.9892 and RMSE of 1.2738 mg/L. This demonstrates the model’s strong generalization ability in overcoming the physical limitations of optical probes. This method effectively identifies and quantifies copper ions in water samples, demonstrating good accuracy and stability.

With the growing demand for high-performance lithium-ion batteries, developing energy-efficient and simple synthesis methods to enhance the electrochemical performance of LVO (LiV₃O₈) has become a critical challenge. This study presents an low-temperature fluoride salt solid-state synthesis method, utilizing lithium fluoride (LiF) simultaneously as both the lithium source and flux. This approach initiates the formation of lithium trivanadate (LVO) at 400 °C and achieves complete reaction at 550 °C, enabling the one-step direct preparation of pure-phase, microrod-shaped LVO with a high oxygen vacancy concentration (approximately 16.5 at. %). Electrochemical performance tests demonstrate that the material delivers specific discharge capacities of 335.5, 333.9, 313.6, 249.5, 174.5, 144.3, 129.9, and 109.1 mAh g^-1 at current densities of 50, 100, 200, 400, 800, 1200, 1500, and 2000 mA g^-1, respectively. Notably, at a high rate of 1000 mA g^-1 during long-cycle testing, the material maintains an initial capacity of 156.3 mAh g^-1, with a capacity retention of 83.17% after 400 cycles. The excellent electrochemical performance of this material can be attributed to its unique microrod-shaped morphology and the introduced high concentration of oxygen vacancy defects, which synergistically enhance lithium-ion storage kinetics and structural stability. The developed one-step low-temperature synthesis strategy successfully achieves the controllable preparation of LVO integrating both high oxygen vacancy concentration and a microrod morphology, providing a pathway for the design and synthesis of high-performance lithium-ion battery cathode materials.