Photochemical Processes Research Articles

Transformation of persistent organic micropollutants by UV and UV/H2O2 in wastewater treatment plant effluent

ABSTRACT Photochemical and advanced oxidation processes (AOPs) are promising options to simultaneously disinfect wastewater treatment plant (WWTP) effluent and degrade organic micropollutants (OMPs). In the present study, kinetic experiments with UV alone and the combination of UV and hydrogen peroxide (H2O2) as an AOP were conducted in WWTP effluent (with and without ultrafiltration) to assess the degradation of 24 OMP, 13 of which were examined for the first time, in a flow-through batch reactor setup. Four parameters were systematically varied to quantify their impacts on OMP degradation: H2O2 concentrations, UV source, water matrix, and flow rate. Most of the studied OMPs (e.g., trimethylammonium, 1,3-di-o-tolylguanidine, carbamazepine) were only significantly degraded in the presence of UV radiation and H2O2. The highest pseudo-first-order rate constants were found for diclofenac, acesulfame, diatrizoate, and sulfamethoxazole. The experiment with the highest degradation also showed the strongest abatement of UV absorbance at 254 nm. Only three of the 24 substances (cyanoguanidine, melamine, and oxipurinol) were not degraded; UV alone even increased their concentrations. Overall, upgrading a UV disinfection to an AOP using H2O2 allows the degradation of a wide range of OMP, making it an interesting process for water reuse.

Unraveling Photoinduced Desorption Dynamics of π-Conjugated Ligands in ZnS Nanocrystals via Pump-Push-Probe Spectroscopy.

The photoinduced ligand desorption from nanocrystal (NC) surfaces plays a critical role in the diverse functionalities of NCs. However, this reaction is inherently complex because photophysical and photochemical reactions are involved, and many aspects remain elusive. In this study, using ZnS NCs coordinated with perylenebisimide (PBI) ligands as a model system, we revealed that pump-push-probe spectroscopy provides detailed insights into the transient species following photoinduced ligand desorption reactions. This method successfully isolated the signal of the PBI radical anion, generated by photoinduced charge separation, which was difficult to identify by conventional pump-probe spectroscopy. Furthermore, pump-push-probe spectroscopy also revealed that the transiently formed aggregation of PBI after PBI desorption is the H-type aggregate. This research is expected to contribute to the analysis of complex photochemical reaction processes in composite nanomaterials and is important for the development of highly efficient NC photocatalysts and photodurable NCs.

ALMA and GMRT Studies of Dust Continuum Emission and Spectral Lines Toward Oort Cloud Comet C/2022 E3 (ZTF)

The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways: (i) the outgassing from the nucleus, (ii) the photochemical process, and (iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3 (ZTF) using the Giant Metrewave Radio Telescope (GMRT) band L and the Atacama Large Millimeter/submillimeter Array (ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen (H I) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol (CH3OH) from comet C/2022 E3 (ZTF). From the dust continuum emission, the dust production (Afρ) activity of comet ZTF is 2280 ± 50 cm. Based on LTE spectral modeling, the column density and excitation temperature of CH3OH toward C/2022 E3 (ZTF) are (4.50 ± 0.25) × 1014 cm−2 and 70 ± 3 K respectively. The integrated emission maps show that CH3OH was emitted from the coma region of the comet. The production rate of CH3OH toward C/2022 E3 (ZTF) is (7.32 ± 0.64) × 1026 molecules s−1. The fractional abundance of CH3OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH3OH with the existence modeled value, and we see the observed and modeled values are quite similar. We claim that CH3OH is formed via the subsequential hydrogenation of formaldehyde (H2CO) on the grain surface of comet C/2022 E3 (ZTF).

Icelandic glacial dissolved organic carbon fluxes, composition and variability - relevance for the global glacial carbon budget

Despite their relatively large size, organic carbon (OC) fluxes from Icelandic glaciers have not been explicitly considered in current global glacial OC flux calculations. Most global glacial OC estimates are based on limited individual flux estimates, which show considerable spatial differences, are often based on melt season fluxes, and rarely account for seasonal and diurnal variability of glacial dissolved organic matter (DOM). Using an annual dataset of 25 Icelandic glaciers (and their glacial streams) we investigate DOM concentration and composition, calculating an estimate for downstream OC fluxes from Icelandic glaciers, considering diurnal and seasonal variability. DOM source and composition distinctly changed from a terrestrial character toward a more proteinaceous character as melt increased, both on a seasonal and diurnal basis, likely reflecting the flow path of the meltwater. While DOC concentration did not change on a diurnal basis, DOM composition was more labile in the afternoons, possibly indicating photochemical or biological transformation processes. Overall, the glacial streams predominantly acted as CO2 sinks. However, higher DOC concentrations, along with contributions of more proteinaceous DOM in proglacial streams, led to a decrease in the uptake potential for CO2. Finally, we estimated an export flux of 0.0026 ± 0.0029 Gg C yr−1 km−2 of DOC, and 0.011 ± 0.007 Tg C yr−1 km−2 of POC, from Icelandic glaciers. We reveal larger than previously assumed DOC and POC fluxes from Icelandic glaciers, with higher-than-global-average areal fluxes (~3 % and 9 % of global glacial C flux respectively). Our findings underscore the importance of revising current global estimates to include the not-fully-accounted-for contribution of Icelandic, and other glaciers. This is particularly important considering ongoing climatic changes will likely affect glacial meltwater discharge and sources, leading to altered DOM composition and DOC concentration, having potentially considerable consequences for glacial OC export and CO2 uptake potentials of glacial streams.

Selective light-driven methane oxidation to ethanol

Methane (CH4) photocatalytic upgrading to value-added chemicals, especially C2 products, is significant yet challenging due to sluggish energy/mass transfer and insufficient chemical driven-force in single photochemical process. Herein, we realize solar-driven CH4 oxidation to ethanol (C2H5OH) on crystalline carbon nitride (CCN) modified with Cu9S5 and Cu single atoms (Cu9S5/Cu-CCN). The integration of photothermal effect and photocatalysis overcomes CH4-to-C2H5OH conversion bottlenecks, with Cu9S5 as a hotspot to convert solar-energy to heat. In-situ characterizations demonstrate that Cu single atoms play as electron acceptor for O2 reduction to ·OOH/ · OH, while Cu9S5 acts as hole acceptor and site for CH4 adsorption, C − H activation, and C − C coupling. Theoretical calculations demonstrate that Cu9S5/Cu-CCN reduces C − C coupling energy barrier by stabilizing ·CH3 and ·CH2O. Impressively, C2H5OH productivity reaches 549.7 μmol g–1 h–1, with selectivity of 94.8% and apparent quantum efficiency of 0.9% (420 nm). This work provides a sustainable avenue for CH4 conversion to value-added chemcials.

Decadal changes in summer aerosol composition and secondary aerosol formation mechanisms in Beijing

Abstract Aerosol chemistry in China has undergone significant transformation due to stringent emission control measures, leading to great shifts in aerosol composition and formation mechanisms. This study investigates the summer chemical evolution of aerosol species in Beijing over the past decade based on two summertime measurements using aerosol chemical speciation monitors. The results reveal a substantial decrease in fine particulate matter concentrations by 72.7% in summer over the past decade, particularly primary species that dropped by 86.3-95.1%. However, this improvement in particulate matter was accompanied by a worsening of ozone pollution between 2011 and 2022. In contrast, secondary components such as sulfate and secondary organic aerosol (SOA) exhibited significant increases in their contributions, rising from 18.2-25.5% to 21.4-41%. The varying responses of aerosol species to emission reductions are closely tie to changes in emission sources, aerosol chemistry, and meteorology. By decoupling the influence of meteorology through machine learning, our analysis highlights the crucial role of emission reductions in improving air quality, though with different impacts on aerosol chemistry. The dominant formation mechanisms of secondary components varied between the two summers, likely influenced by shifts in aerosol liquid water content and atmospheric oxidation capacity due to NOx reductions. Compared to the summer of 2011, the formation of sulfate and SOA in summer 2022 was primarily driven by photochemical processes related to ozone, with less impacts from aqueous-phase formation, while nitrate was predominantly formed via N2O5 heterogeneous hydrolysis. Considering the complex nature of secondary aerosol formation, future summer pollution control strategies should prioritize stricter collaborative regulation of precursors for both secondary aerosol and ozone.

Elucidating Interplay of Chemical and Metal Interface Damping in Single Gold Nanorods Coated with an Ultrathin Palladium Shell.

Understanding plasmon damping pathways in gold nanoparticles is crucial for its efficient utilization in photochemical processes and biosensing experiments. However, elucidating the competition and interplay between chemical and metal interface damping pathways remains a significant challenge. Herein, we investigate the plasmon decay pathways of thiolated ultrathin palladium (Pd)-coated gold nanorods (AuNRs@Pd) by using dark-field (DF) spectroscopy and surface-enhanced Raman spectroscopy (SERS). AuNRs@Pd were synthesized via bottom-up epitaxial Pd growth at five Pd precursor concentrations. The resulting AuNRs@Pd exhibited a redshift and line width broadening in the DF scattering spectra as the Pd loading on the nanoparticles increased. The attachment of thiol adsorbates (thiophenol) to the nanoparticle surface induced further redshift and narrowed the line width, which was particularly pronounced with increased Pd loading. Electron-withdrawing adsorbates (p-nitrothiophenol) on the nanoparticle surface led to line width narrowing and redshift, attributed to reduced electron density on the AuNR core lattices. This electron density reduction was confirmed through SERS, with AuNRs@Pd53 demonstrating the highest enhancement factor at four Raman peak points. Therefore, we elucidate plausible plasmon decay pathways under the coexistence of chemical interface damping and metal interface damping in single AuNRs@Pd.

Exploring the photocatalytic performance of (CH3NH3)2AgInBr6, a Pb-free perovskite, and the composite with a MgAlTi layered double hydroxide for air purification purposes

Pb-free metal halide perovskites (MHPs) have lately been employed in different types of photocatalytic applications due to their high absorption in the visible region and excellent electrochemical properties. In this work, the In-based (CH3NH3)2AgInBr6 (MAIB) perovskite has been synthesized using a solvent-free mechanochemical method and the photocatalytic activity has been assessed in the NO removal reaction. The ball milling approach has been employed to obtain microcrystals with a high degree of crystallinity. The diffuse reflectance spectroscopy reveals a band gap energy of 3.44 eV but with an absorption tail covering the visible region. The photocatalytic experiments reveal a high NO abatement of 92 % and 32 % under UV-Vis and visible irradiation, respectively. The cyclability of the MAIB material was investigated during six cycles obtaining an almost nearly constant performance. In a novel approach, the low selectivity showed by the MAIB perovskite in the DeNOx process was circumvented by the preparation of a composite with the MgAlTi layered double hydroxide (LDH). The presence of MgAlTi-LDH avoids the release of NO2 during the photochemical oxidation of the NO gas. Under visible light, the MAIB perovskite is the active species leading to the production of superoxide radicals, which initiate the photochemical process. The MAIB/LDH composite exhibited good efficiency and outstanding selectivity to remove NO gas, together with long-term stability when irradiated under visible light.

Visible Light‐Mediated [4+2] Annulation of Silylimines with Olefins to 1‐Aminotetralins Enabled by Diradical Hydrogen Atom Transfer of C−H Bonds

A facile photochemical, one‐pot synthesis of highly functionalized 1‐aminotetralins derivatives (> 70 examples) from readily accessible o‐alkyl and o‐formyl aryl silylimines with olefins is described. A diradical‐mediated hydrogen atom transfer (DHAT) of primary, secondary, and tertiary C(sp3)−H bonds of o‐alkyl arylsilylimines and C(sp2)−H bonds of o‐formyl arylsilylimines enabled a [4+2] annulation with olefins in excellent diastereoselectivity. This was accomplished upon irradiation at λ = 420 nm in the presence of thioxanthen‐9‐one (10 mol%) as the sensitizer via energy transfer. Moreover, sulfur‐substituted o‐alkyl silylimines can undergo such photochemical process in the absence of an external photosensitizer. This effective protocol is compatible with a variety of functional groups and can be applied to the modification of bioactive molecules. Based on mechanistic evidences and computational studies, it is suggested that the silyl substituent enables an efficient energy transfer leading to the formation of a key C,N‐diradical and subsequent [4+2]‐cyclization was supported by a better molecular orbital matching between the HSOMO of the 1,4‐diradical intermediate and the LUMO of the olefins. Thus, upon irradiation, the excited silylimine unlocks a carbon‐to‐nitrogen DHAT and subsequent [4+2] cyclization that allows the divergent functionalization of benzylic C(sp3)−H bonds and C(sp2)−H bonds.

Visible Light-Mediated [4+2] Annulation of Silylimines with Olefins to 1-Aminotetralins Enabled by Diradical Hydrogen Atom Transfer of C-H Bonds.

A facile photochemical, one-pot synthesis of highly functionalized 1-aminotetralins derivatives (> 70 examples) from readily accessible o-alkyl and o-formyl aryl silylimines with olefins is described. A diradical-mediated hydrogen atom transfer (DHAT) of primary, secondary, and tertiary C(sp3)-H bonds of o-alkyl arylsilylimines and C(sp2)-H bonds of o-formyl arylsilylimines enabled a [4+2] annulation with olefins in excellent diastereoselectivity. This was accomplished upon irradiation at λ = 420 nm in the presence of thioxanthen-9-one (10 mol%) as the sensitizer via energy transfer. Moreover, sulfur-substituted o-alkyl silylimines can undergo such photochemical process in the absence of an external photosensitizer. This effective protocol is compatible with a variety of functional groups and can be applied to the modification of bioactive molecules. Based on mechanistic evidences and computational studies, it is suggested that the silyl substituent enables an efficient energy transfer leading to the formation of a key C,N-diradical and subsequent [4+2]-cyclization was supported by a better molecular orbital matching between the HSOMO of the 1,4-diradical intermediate and the LUMO of the olefins. Thus, upon irradiation, the excited silylimine unlocks a carbon-to-nitrogen DHAT and subsequent [4+2] cyclization that allows the divergent functionalization of benzylic C(sp3)-H bonds and C(sp2)-H bonds.

Photo-induced carboxylation of C(sp2)−S bonds in aryl thiols and derivatives with CO2

Aryl thiols have proven to be a useful class of electron donors and hydrogen atom sources in photochemical processes. However, the direct activation and functionalization of C(sp2)–S bonds in aryl thiols remains elusive in the field of photochemistry. Herein, a photochemical carboxylation of C(sp2)–S bonds in aryl thiols with CO2 is reported, providing a synthetic route to important aryl carboxylic acids. Moreover, different kinds of aryl thiol derivatives, benzeneselenol and diphenyl diselenide also show moderate-to-high reactivity in this transformation. Mechanistic studies, including DFT calculations, suggest that the in situ generated carbon dioxide radical anion (CO2•−) and disulfide might be the key intermediates, which undergo radical substitution to yield products. This reaction features mild and catalyst-free conditions, good functional group tolerance and wide substrate scope. Furthermore, the efficient degradation of polyphenylene sulfide highlights the usefulness of this methodology.

Bioprospecting a Natural Antioxidant Peptide for Tomato Biostimulation Under Water Limitations: Physiological Approach

AbstractDrought causes major agricultural losses, threatening food security worldwide. Thus, innovative strategies have been explored to improve crop tolerance to drought. This work focused on one natural peptide (PpT-2) with antioxidant activity, unexplored in plant applications, to evaluate its effectiveness in mitigating drought effect on Solanum lycopersicum L. plants. For that, tomato plants were foliar sprayed with different doses of PpT-2 (0, 15 or 150 mg L−1) and exposed to water Stressed and UnStressed conditions. The plant growth, photosynthesis and oxidative stress-related parameters were evaluated. Plant treatment with PpT-2, mostly at the highest concentration, alleviated diverse effects induced by water restriction: stimulated CO2 assimilation; improved ΦPSII, Fv/Fm and Fv’/Fm’; amended net CO2 assimilation rate and water use efficiency; restricted H2O2 accumulation and lipid peroxidation; stimulated SOD activity. Under UnStressed conditions, PpT-2 induced some degree of stomatal closure, nevertheless without restricting CO2 availability for the non-photochemical processes of photosynthesis, besides of decreasing H2O2 content and CAT activity. Overall, PpT-2 application controlled H2O2 accumulation, and under water limitations improved both photochemical and non-photochemical processes of photosynthesis and promoted drought tolerance, underscoring its potential for managing drought stress in crop species.

Unveiling photochemical CO2 reduction processes on PbBiO2I/GO surfaces: Insights from in-situ Raman spectroscopy

Bismuth-based materials are increasingly valued for their dual capability in catalyzing the photochemical CO2 reduction reaction (CO2RR) and enhancing the selectivity towards multi-carbon (C2+) products. This study introduces a novel PbBiO2I/graphene oxide (PbBiO2I/GO) composite, synthesized to leverage the unique properties of both components for improving catalytic performance. The physical and chemical properties of these composites were characterized to delineate their functionality and interaction mechanisms. The heterojunction structure in the composites significantly facilitated the CO2RR, with a noted CH4 conversion rate of 0.8376 µmolg−1h−1. This rate is significantly higher ∼1.78 times that of standalone PbBiO2I under similar conditions. Advanced X-ray photoelectron spectroscopy (XPS) analysis indicated that the incorporation of graphene oxide enhances the electronic environment around Pb2+ and Bi3+ ions, reducing their charge states and increasing oxygen vacancies. This modification likely contributes to the observed catalytic enhancement. Furthermore, in-situ Raman spectroscopy provided insights into the dynamic formation of key intermediates during the CO2RR. Under targeted light irradiation, distinct intermediates such as *COO−, *CO, H*CO/H*COH, OC*C*O, O*CCHO, and C–H were detected, facilitating a deeper understanding of the mechanistic pathways involved in C1 and C2 product formation. This comprehensive analysis not only elucidates the enhanced catalytic pathways facilitated by the composite structure but also sets a foundation for future optimizations in bismuth-based photocatalytic systems.

Azopyridine Polymers in Organic Phase Change Materials for High Energy Density Photothermal Storage and Controlled Release.

Azo-compounds molecules and phase change materials offer potential applications for sustainable energy systems through the storage and controllable release photochemical and phase change energy. Developing novel and highly efficient Azo-based solar thermal fuels (STFs) for photothermal energy storage and synergistic cooperation with organic phase change materials present significant challenges. Herein, three types of (ortho-, meta-, and para-) azopyridine polymers hinged with flexible alkyl chain are synthesized, in which meta-azopyridine polymer exhibits striking photothermal storage capacity of 430 J/g, providing a feasibility solution for developing high energy density Azo-based STFs. Furthermore, a stable two-phase hybrid system was innovatively constructed by combining the meta-azopyridine polymer with organic phase change materials leveraging hydrogen bonds and van der Waals interactions to collectively harness phase change energy and photothermal energy. The organic phase change material not only supplies additional phase change latent heat but also serves as a solvent, offering abundant free volume for the photo-induced isomerization of the azopyridine chromophores, which successfully circumvents the low charging efficiency in the condensed state and reliance on solvent-assisted charging in traditional Azo-based STFs. This study demonstrates the energy distribution and utilization for household consumers and the photothermal-assisted insulation strategy, achieving more extensive potential implementation for STFs.

Azopyridine Polymers in Organic Phase Change Materials for High Energy Density Photothermal Storage and Controlled Release

Azo‐compounds molecules and phase change materials offer potential applications for sustainable energy systems through the storage and controllable release photochemical and phase change energy. Developing novel and highly efficient Azo‐based solar thermal fuels (STFs) for photothermal energy storage and synergistic cooperation with organic phase change materials present significant challenges. Herein, three types of (ortho‐, meta‐, and para‐) azopyridine polymers hinged with flexible alkyl chain are synthesized, in which meta‐azopyridine polymer exhibits striking photothermal storage capacity of 430 J/g, providing a feasibility solution for developing high energy density Azo‐based STFs. Furthermore, a stable two‐phase hybrid system was innovatively constructed by combining the meta‐azopyridine polymer with organic phase change materials leveraging hydrogen bonds and van der Waals interactions to collectively harness phase change energy and photothermal energy. The organic phase change material not only supplies additional phase change latent heat but also serves as a solvent, offering abundant free volume for the photo‐induced isomerization of the azopyridine chromophores, which successfully circumvents the low charging efficiency in the condensed state and reliance on solvent‐assisted charging in traditional Azo‐based STFs. This study demonstrates the energy distribution and utilization for household consumers and the photothermal‐assisted insulation strategy, achieving more extensive potential implementation for STFs.

Vertical Distribution, Diurnal Evolution, and Source Region of Formaldehyde During the Warm Season Under Ozone-Polluted and Non-Polluted Conditions in Nanjing, China

Formaldehyde (HCHO), a key volatile organic compound (VOC) in the atmosphere, plays a crucial role in driving photochemical processes. Satellite-based observations of column concentrations of HCHO and other gaseous pollutants (e.g., NO2) have generally been used in previous studies to elucidate the mechanisms behind secondary organic aerosol (SOA) and ozone (O3) formation. This study aimed to investigate the characteristics of HCHO by retrieving its vertical profile over Nanjing during the warm season (May–June 2022) and analyzing the diurnal variation in vertical distribution and potential source regions on non-polluted (MDA8 O3 < 160 μg m−3, NO3P) and O3-polluted (MDA8 O3 ≥ 160 μg m−3, O3P) days. Under both conditions, HCHO was primarily concentrated below 1.5 km altitude, with average vertical profiles displaying similar Boltzmann-like distributions. However, HCHO concentrations on O3P days were 1.2–1.6 times higher than those on non-polluted days at the same altitude below 1.5 km. Maximum HCHO concentrations occurred in the afternoon, while the peak value in the 0.1–0.4 km layers was reached around noon (~11:00 a.m.). The variation rates (VR) of HCHO in the 0.3–1.2 km altitudes had a maximum on O3P days (approximately 0.33 ppbv h−1), and were significantly higher (p < 0.01) than the VR observed on NO3P days (0.14–0.20 ppbv h−1). The analysis of footprints showed that HCHO concentrations were jointly influenced by the upstream region and the surroundings of the study site. The study results improve the understanding of the vertical distribution and potential source regions of HCHO.

Precise Photochemical Post‐Processing of Molecular Crystals

Molecular crystals carry a great potential as new soft smart materials, with a plethora of recent examples overcoming the major obstacle of mechanical flexibility, and this research direction holds enormous potential to revolutionize optics, electronics, medicine, and space exploration. However, shaping organic crystals into desired shapes and sizes remains a major practical challenge due to the lack of control over the crystallization process, and the difficulties in mechanical post‐processing without introduction of defects that are usually imparted by their soft nature. Here we present an innovative approach that employs photochemical processing for precise and nondestructive cutting of a molecular crystal. Our proposed method uses light to post‐process crystals of the desired size and shape, similar to using light to cut other materials. This reaction induces strain, ensuring sharp cleavage without the need for melting or other processes. We further demonstrate the potential of this approach by producing crystals of arbitrary size, which can be used as controllable optical waveguides. Among other potential applications, this method can be used to prepare dynamic crystals, particularly those with aspect ratios crucial for mechanical deformation, such as flexible electronics, soft robotics, and sensing.

Precise Photochemical Post-Processing of Molecular Crystals.

Molecular crystals carry a great potential as new soft smart materials, with a plethora of recent examples overcoming the major obstacle of mechanical flexibility, and this research direction holds enormous potential to revolutionize optics, electronics, medicine, and space exploration. However, shaping organic crystals into desired shapes and sizes remains a major practical challenge due to the lack of control over the crystallization process, and the difficulties in mechanical post-processing without introduction of defects that are usually imparted by their soft nature. Here we present an innovative approach that employs photochemical processing for precise and nondestructive cutting of a molecular crystal. Our proposed method uses light to post-process crystals of the desired size and shape, similar to using light to cut other materials. This reaction induces strain, ensuring sharp cleavage without the need for melting or other processes. We further demonstrate the potential of this approach by producing crystals of arbitrary size, which can be used as controllable optical waveguides. Among other potential applications, this method can be used to prepare dynamic crystals, particularly those with aspect ratios crucial for mechanical deformation, such as flexible electronics, soft robotics, and sensing.

Synergistic effect between amino functional group and graphene oxide in selective photocatalytic CO2 reduction to formic acid

Carbon dioxide (CO2) reduction to useful possible chemicals is of great significance to energy supply, while formic acid is one of the most desirable product among the many other chemicals. In this study, a novel reduced graphene oxide (rGO) coupled doped TiO2 with NH2-MIL-125(Ti)(TiM) composite photocatalysts TiO2@rGO@TiM was designed by using a solvent-thermal method to facilitate the photocatalytic CO2 reduction to formic acid under the visible light. Benefiting from the special structure of TiO2@rGO@TiM, up to a rate of 113 µmol•g−1•h−1 of formic acid was produced in a photochemical process, which is four times greater than that of pure TiO2 and TiM without any sacrificial agent. The results of structure and photoelectrochemical characterization demonstrated that the enhanced production of formic acid was attributable to the synergistic effect generated by the incorporation of the amino functional group and reduced graphene oxide, resulting in the effective photo-induced carrier spatial segregation and transfer and improving the catalytic activity.

How Sophisticated Are Neural Networks Needed to Predict Long-Term Nonadiabatic Dynamics?

Nonadiabatic dynamics is key for understanding solar energy conversion and photochemical processes in condensed phases. This often involves the non-Markovian dynamics of the reduced density matrix in open quantum systems, where knowledge of the system's prior states is necessary to predict its future behavior. In this study, we explore time-series machine learning methods for predicting long-time nonadiabatic dynamics based on short-time input data, comparing these methods with the physics-based transfer tensor method (TTM). To understand the impact of memory time on these approaches, we demonstrate that non-Markovian dynamics can be represented as a linear map within the Nakajima-Zwanzig generalized quantum master equation framework. We further propose a practical method to estimate the effective memory time, within a given tolerance, for reduced density matrix propagation. Our predictive models are applied to various physical systems, including spin-boson models, multistate harmonic (MSH) models with Ohmic spectral densities and for a realistic organic photovoltaic system composed of a carotenoid-porphyrin-fullerene triad dissolved in tetrahydrofuran. Results indicate that the simple linear-mapping fully connected neural network (FCN) outperforms the more complicated nonlinear-mapping networks including the gated recurrent unit (GRU) and the convolutional neural network/long short-term memory (CNN-LSTM) in systems with short memory times, such as spin-boson and MSH models. Conversely, the nonlinear CNN-LSTM and GRU models yield higher accuracy in the triad MSH systems characterized by long memory times. These findings offer valuable insights into the role of effective memory time in non-Markovian quantum dynamics, providing practical guidance for the application of time-series machine learning models to complex chemical systems.