Solution Plasma Synthesis of High-Entropy Alloy Nanoparticles with Self-Limiting Oxidation for Photothermal CO2 Reduction.

Engineering multimetallic nanocatalysts with the entropy-mediated strategy to reduce reaction activation energy is regarded as an innovative and effective approach to facilitate efficient heterogeneous catalysis. Accordingly, conformational entropy-driven high-entropy alloys (HEAs) are emerging as a promising candidate to settle the catalytic efficiency limitations of nanozymes, attributed to their versatile active site compositions and synergistic effects. As proof of the high-entropy nanozymes (HEzymes) concept, elaborate PdMoPtCoNi HEA nanowires (NWs) with abundant active sites and tuned electronic structures, exhibiting peroxidase-mimicking activity comparable to that of natural horseradish peroxidase are reported. Density functional theory calculations demonstrate that the enhanced electron abundance of HEA NWs near the Fermi level (EF) is facilitated via the self-complementation effect among the diverse transition metal sites, thereby boosting the electron transfer efficiency at the catalytic interface through the cocktail effect. Subsequently, the HEzymes are integrated with a portable electronic device that utilizes Internet of Things-driven signal conversion and wireless transmission functions for point-of-care diagnosis to validate their applicability in digital biosensing of urinary biomarkers. The proposed HEzymes underscore significant potential in enhancing nanozymes catalysis through tunable electronic structures and synergistic effects, paving the way for reformative advancements in nano-bio analysis.

High entropy alloys (HEA) have garnered significant attention in electromagnetic wave (EMW) absorption due to their efficient synergism among multiple components and tunable electronic structures. However, their high density and limited chemical stability hinder their progress as lightweight absorbers. Incorporating HEA with carbon offers a promising solution, but synthesizing stable HEA/carbon composite faces challenges due to the propensity for phase separation during conventional heat treatments. Moreover, EMW absorption mechanisms in HEAs may be different from established empirical models due to their high-entropy effect. This underscores the urgent need to synthesize stable and lightweight HEA/carbon absorbers and uncover their intrinsic absorption mechanisms. Herein, we successfully integrated a quinary FeCoNiCuMn HEA into a honeycomb-like porous carbon nanofiber (HCNF) using electrostatic spinning and the Joule-heating method. Leveraging the inherent lattice distortion effects and honeycomb structure, the HCNF/HEA composite demonstrates outstanding EMW absorption properties at an ultralow filler loading of 2 wt %. It achieves a minimum reflection loss of -65.8 dB and boasts a maximum absorption bandwidth of up to 7.68 GHz. This study not only showcases the effectiveness of combining HCNF with HEA, but also underscores the potential of Joule-heating synthesis for developing lightweight HEA-based absorbers.

Facilitating the charge separation of semiconductor photocatalysts to increase the photocatalytic CO2 reduction activity has become a great challenge for sustainable energy conversion. Herein, the surface halogen-modified defect-rich Bi2 WO6 nanosheets have been successfully prepared to address the aforementioned challenge. Importantly, the modification of surface with halogen atoms is beneficial for the adsorption and activation for CO2 molecules and charge separation. These properties have been analyzed by experimental and theoretical methods. DFT calculations revealed that the modification of the Bi2 WO6 surface with Br atoms can decrease the formation energy of the *COOH intermediate, which accelerates CO2 conversion. All halogen-modified defect-rich Bi2 WO6 nanosheets showed an enhanced photocatalytic CO2 reduction activity. Specifically, Br-Bi2 WO6 exhibited the best CO generation rate of 13.8 μmol g-1 h-1 , which is roughly 7.3 times as high as the unmodified defect-rich Bi2 WO6 (1.9 μmol g-1 h-1 ). Moreover, in the presence of a cocatalyst (cobalt phthalocyanine) and a sacrificial agent (triethanolamine), Br-Bi2 WO6 exhibited an even further improved CO generation rate of 187 μmol g-1 h-1 . This finding provides a new approach to optimize the CO2 reduction pathway of semiconductor photocatalysts, which is beneficial to develop highly efficient CO2 reduction photocatalysts.

Photocatalytic reduction of CO2 with H2O provides a promising and sustainable pathway to produce valuable chemicals and fuels. However, the low efficiency of CO2 reduction and the concomitant competition of H2 evolution pose serious challenges to practical applications. Herein, a novel approach is proposed to modulate the surface microenvironment of photocatalysts by utilizing hydrogen peroxide (H2O2). A bronze‐phase TiO2 (TB) composed of ultrathin nanosheet with a thickness of ∼3 nm is fabricated and employed as the model catalyst for photocatalytic CO2 reduction. H2O2 molecules are presumed to be bonded to the ultrathin TB surface to form the TB‐H2O2 (TBHO) active specie. The newly generated TBHO enhances the CO2 adsorption and accelerates mass transfer, and the weakly acidic microenvironment of the catalyst surface serves the purpose of mediating the proton‐coupled electron transfer path. Consequently, ultrathin TB nanosheets assisted by H2O2 show an excellent CO generation rate of 29.1 µmol−1 g−1 h−1 (which is 11.2‐fold higher than that of pure TB) in water, and the selectivity toward CO is nearly 100%. This work underscores the importance of tailoring the catalyst surface microenvironment to promote the CO2 reduction while minimizing the H2 generation in pure water.

The photocatalytic reduction of CO2 using solar energy presents an effective strategy for CO2 mitigation and utilization. Metal-organic frameworks (MOFs), known for their exceptional CO2 adsorption capacities and unique structural features, are emerging as novel photoactive materials for CO2 reduction. In this study, rod-like, reticular, and ball-like Ni-BTC were synthesized using Ni2⁺ ions and 1,3,5-benzenetricarboxylic acid (H₃BTC). Among these, the rod-like Ni-BTC exhibited the narrowest optical band gaps and achieved an outstanding CO generation rate of 4.707mmol/g/h. To further enhance the photocatalytic performance, Co2⁺ was partially substituted for Ni2⁺ in the rod-like Ni-BTC, resulting in the construction of bimetallic coral-like Co/Ni-BTC-x (x=1, 2, 3). The incorporation of Co2⁺ facilitated the transformation of the larger rod-like Ni-BTC particles into a coral-like morphology with micro- and nanoscale dimensions. Compared to monometallic rod-like Ni-BTC, the bimetallic catalysts exhibited lower bandgap values, faster charge transfer rates, and superior photocatalytic CO₂ reduction activity. Notably, Co/Ni-BTC-2 achieved the highest CO generation rate of 7.392mmol/g/h. This study demonstrates that the combination of morphological control and bimetallic approach is an effective strategy for enhancing the performance of MOF catalysts in the photochemical reduction of CO2.

Modulating the band structure of semiconductor photocatalysts to increase the photocatalytic CO2 reduction activity has become a great challenge for sustainable energy conversion. Herein, the halogenation-modified defective Bi2WO6 nanosheets have been successfully prepared to address aforementioned challenge. The modification of halogenation atoms can promote the defective Bi2WO6 nanosheets to generate more oxygen defects, and the concentration of oxygen vacancy in Bi2WO6 nanosheets can be controlled by modifying with different halogenation atoms. Importantly, the modification of halogenation atoms can modulate the band structure of Bi2WO6 and optimize the separation and transport of photogenerated carriers. As a result, all the halogenation-modified defective Bi2WO6 nanosheets manifested an enhanced photocatalytic CO2 reduction activity. Specially, the Br-Bi2WO6 exhibited the best CO generation rate of 13.8 μmol g-1 h-1, and displayed roughly 7.3 times as high as that of defective Bi2WO6 (1.9 μmol g-1 h-1). Moreover, in the coexistence of cocatalysts (CoPc) and sacrificial agents (TEOA), the Br-Bi2WO6 exhibited superior CO generation rate of 187 μmol g-1 h-1. This finding provides a new approach to simultaneously modulate the concentration of oxygen vacancy and band structure of semiconductor photocatalysts, developing highly efficient CO2 reduction photocatalysts.

CO2 photoreduction into valuable chemicals is a sustainable and prospective technology to alleviate greenhouse effects and the energy crisis. However, the photocatalytic efficiency is impeded by undesirable recombination of photogenerated carriers and poor CO2 activation performance. Herein, oxygen vacancies (OVs) are introduced into BiOBr atomic layers by ultraviolet light assisting to increase the efficiency of carrier separation and CO2 adsorption–activation performance, enhancing the CO2 reduction activity. The introduction of OVs can effectively enhance the visible light absorption, boost the photogenerated carrier separation migration, and tune the adsorption/desorption process for CO2 and products on the surface of photocatalysts. The optimized OVs engineering–mediated photocatalyst achieves a high CO generation rate of 10.15 μmol g−1 under visible light irradiation for 5 h in pure water, which is 1.99 times compared with that of pristine BiOBr atomic layers. The possible photocatalytic mechanism is investigated by in situ Fourier transform infrared spectroscopy (in situ FT‐IR) spectrometry. Also, an opportunity to design OVs‐rich ultrathin semiconductors for high‐performance CO2 reduction is offered.

Surface defects in semiconductors have a significant role to tune the photocatalytic reactions. However, the dominant studied defect type is oxygen vacancy, and metal cation vacancies are seldom explored. Herein, bismuth vacancies are engineered into BiOBr through ultrathin structure control and employed to tune photocatalytic CO2 reduction. VBi-BiOBr ultrathin nanosheets deliver a high selective CO generation rate of 20.1 μmol g-1 h-1 in pure water, without any cocatalyst, photosensitizer, and sacrificing reagent, roughly 3.8 times higher than that of BiOBr nanosheets. The increased CO2 reduction activity is ascribed to the tuned electronic structure, optimized CO2 adsorption, activation, and CO desorption process over VBi-BiOBr ultrathin nanosheets. This work offers new opportunities for designing surface metal vacancies to optimize the CO2 photoreduction performances.

Designing photocatalysts with efficient charge transport and abundant active sites for photocatalytic CO2 reduction in pure water is considered a potential approach. Herein, a nickel-phthalocyanine containing Ni-N4 active sites-based conjugated microporous polymer (NiPc-CMP), offering highly dispersed metal active sites, satisfactory CO2 adsorption capability, and excellent light harvesting properties, is engineered as a photocatalyst. By virtue of the covalently bonded bridge, an atomic-scale interface between the NiPc-CMP/Bi2 WO6 Z-scheme heterojunction withstrong chemical interactions is obtained. The interface creates directional charge transport highways and retains a high redox potential, thereby enhancing the photoexcited charge carrier separation and photocatalytic efficiency. Consequently, the optimal NiPc-CMP/Bi2 WO6 (NCB-3) achieves efficient photocatalytic CO2 reduction performance in pure water under visible-light irradiation without any sacrificial agent or photosensitizer, affording a CO generation rate of 325.9µmol g-1 with CO selectivity of 93% in 8h, outperforming those of Bi2 WO6 and NiPc-CMP, individually. Experimental and theoretical calculations reveal the promotion of interfacial photoinduced electron separation and the role of Ni-N4 active sites in photocatalytic reactions. This study presents a high-performance CMP-based Z-scheme heterojunction with an effective interfacial charge-transfer route and rich metal active sites for photocatalytic CO2 conversion.

Efficient and stable electrocatalytic hydrogen evolution reaction (HER) at high current densities is highly desirable for industrial-scale hydrogen production, which is yet challenging, because of the electrocatalyst with short lifespans during the acidic HER process. Here, a controllable preparation technique is successfully developed to synthesize PdPtRuRhAu high-entropy alloys (HEAs) of various sizes, within the 3.14nm particles (HEA-3.14) demonstrating exceptional catalytic performance and stable hydrogen production at current densities of -500 and -1000 mA·cm-2 with negligible activity loss over 100h. Theoretical calculations indicate that the bridge adsorption site of Pd-Au serves as an ideal location for HER, with HEA-3.14 possessing the highest proportion of such sites, reaching 18.97%. To further analyze the thermodynamic stability of HEAs, an element-encoding machine learning model is developed from over 300000 preprocessed dataset of HEAs that achieving an impressively low RMSE of 58.6°C and a high R2 value of 0.98. By integrating thermodynamic modeling with machine learning methods, the melting point of the PdPtRuRhAu HEAs at 3.14nm (366°C) is predicted, which aligns well with the results obtained from differential scanning calorimetry tests. This work offers new insights and approaches for designing HEAs that reliably produce hydrogen at high current densities.

High-entropy alloys (HEAs) exhibit exceptional catalytic performance due to their complex surface structures. However, the vast number of active binding sites in HEAs, as opposed to conventional alloys, presents a significant computational challenge in catalytic applications. To tackle this challenge, robust methods must be developed to efficiently explore the configurational space of HEA catalysts. Here, we introduce a novel approach that combines alchemical perturbation density functional theory (APDFT) with a graph-based correction scheme to explore the binding energy landscape of HEAs. Our results demonstrate that APDFT can accurately predict binding energies for isoelectronic permutations in HEAs at minimal computational cost, significantly accelerating configurational space sampling. However, APDFT errors increase substantially when permutations occur near binding sites. To address this issue, we developed a graph-based Gaussian process regression model to correct discrepancies between APDFT and conventional density functional theory values. Our approach enables the prediction of binding energies for hundreds of thousands of configurations with a mean average error of 30 meV, requiring a handful of ab initio simulations.

High-entropy alloys (HEAs) are attracting increased attention as an alternative to noble metals for various catalytic reactions. However, it is of great challenge and fundamental importance to develop spatial HEA heterostructures to manipulate d-band center of interfacial metal atoms and modulate electron-distribution to enhance electrocatalytic activity of HEA catalysts. Herein, an efficient strategy is demonstrated to construct unique well-designed HEAs spatial heterostructure electrocatalyst (HEA@Pt) as bifunctional cathode to accelerate oxygen reduction and evolution reaction (ORR/OER) kinetics for Li-O2 batteries, where uniform Pt dendrites grow on PtRuFeCoNi HEA at a low angle boundary. Such atomically connected HEA spatial interfaces engender efficient electrons from HEA to Pt due to discrepancy of work functions, modulating electron distribution for fast interfacial electron transfer, and abundant active sites. Theoretical calculations reveal that electron redistribution manipulates d-band center of interfacial metal atoms, allowing appropriate adsorption energy of oxygen species to lower ORR/OER reaction barriers. Hence, Li-O2 battery based on HEA@Pt electrocatalyst delivers a minimal polarization potential (0.37V) and long-term cyclability (210 cycles) under a cut-off capacity of 1000mAhg-1 , surpassing most previously reported noble metal-based catalysts. This work provides significant insights on electron-modulation and d-band center optimization for advanced electrocatalysts.

The highly efficient spatial carrier separation and abundant active sites are significant for CO2 photocatalytic reduction efficiency. Herein, an ultrathin Bi2O3 nanosheet/Bi2WO6 network heterostructure is successfully synthesized via a covalently bonded epitaxial growth strategy. Due to cosharing of the Bi–O tetrahedron between Bi2O3 and Bi2WO6, this heterostructure exhibits a compact interface, which can provide a highway for the charge transfer and then boost their separation. Moreover, the pores generated from the hierarchical structure afford abundant exposed photocatalytic active sites. Thus, the optimal Bi2O3/Bi2WO6 heterostructure (BOBWO-12) shows superior photocatalytic performance for CO2 reduction with an ultrahigh selectivity as well as the removal of RhB. Notably, the photocatalytic CO generation rate over BOBWO-12 reaches up to 17.39 μmol·g–1·h–1, which is 18.0 and 4.2 times higher than that of bulk-Bi2WO6 and Bi2WO6 nanosheets, respectively, and the selectivity is of about 95.4%. Moreover, the Bi2O3/Bi2WO6 heterostructure also exhibits improved long-term stability, resulting from the firm heterointerface. Our studies present a conventient avenue to construct a high-efficiency heterostructure photocatalyst with a firm interface by the covalently bonded epitaxial growth method for CO2 reduction.

Transition metal phosphosulfides (TMPSs) have gained much interest due to their highly enhanced photocatalytic activities compared to their corresponding phosphides and sulfides. However, the application of TMPSs on photocatalytic CO2 reduction remains a challenge due to their inappropriate band positions and rapid recombination of photogenerated electron-hole pairs. Herein, we report ultrasmall copper phosphosulfide (us-Cu3P|S) nanocrystals anchored on 2D g-C3N4 nanosheets. Systematic studies on the interaction between us-Cu3P|S and g-C3N4 indicate the formation of an S-scheme heterojunction via interfacial P-N chemical bonds, which acts as an electron transfer channel and facilitates the separation and migration of photogenerated charge carriers. Upon the composite formation, the band structures of us-Cu3P|S and g-C3N4 are altered to enable the enhanced photocatalytic CO generation rate of 137 μmol g-1 h-1, which is eight times higher than that of pristine g-C3N4. The unique phosphosulfide structure is also beneficial for the enhanced electron transfer rate and provides abundant active sites. This first application of Cu3P|S to photocatalytic CO2 reduction marks an important step toward the development of TMPSs for photocatalytic applications.

Photoreduction of CO2 with water into chemical feedstocks of fuels provides a green way to help solve both the energy crisis and carbon emission issues. Metal-organic frameworks (MOFs) show great potential for CO2 photoreduction. However, poor water stability and sluggish charge transfer could limit their application. Herein, three water-stable MOFs functionalized with electron-donating methyl groups and/or electron-withdrawing trifluoromethyl groups are obtained for the CO2 photoreduction. Compared with UiO-67-o-CF3-CH3 and UiO-67-o-(CF3)2, UiO-67-o-(CH3)2 achieves excellent performance with an average CO generation rate of 178.0 μmol g-1 h-1 without using any organic solvent or sacrificial reagent. The superior photocatalytic activity of UiO-67-o-(CH3)2 is attributed to the fact that compared with trifluoromethyl groups, methyl groups could not only elevate CO2 adsorption capacity and reduction potential but also promote photoinduced charge separation and migration. These are evidenced by gas physisorption, photoluminescence, time-resolved photoluminescence, electrochemical impedance spectroscopy, transient photocurrent characteristics, and density functional theory calculations. The possible working mechanisms of electron-donating methyl groups are also proposed. Moreover, UiO-67-o-(CH3)2 demonstrates excellent reusability for the CO2 reduction. Based on these results, it could be affirmed that the strategy of modulating substituent electronegativity could provide guidance for designing highly efficient photocatalysts.