C2 Products Research Articles

Quasi-homogeneous photoelectrochemical organic transformations for tunable products and 100% conversion ratio

Photoelectrochemical (PEC) organic transformation at the anode coupled with cathodic H2 generation is a potentially rewarding strategy for efficient solar energy utilization. Nevertheless, achieving the full conversion of organic substrates with exceptional product selectivity remains a formidable hurdle in the context of heterogeneous catalysis at the solid/liquid interface. Here, we put forward a quasi-homogeneous catalysis concept by using the reactive oxygen species (ROS), such as ·OH, H2O2 and SO4•−, as a charge transfer mediator instead of direct heterogeneous catalysis at the solid/liquid interface. In the context of glycerol oxidation, all ROS exhibited a preference for first-order reaction kinetics. These ROS, however, showcased distinct oxidation mechanisms, offering a range of advantages such as ∼ 100 % conversion ratios and the flexibility to tune the resulting products. Glycerol oxidative formic acid with Faradaic efficiency (FE) of 81.2 % was realized by the H2O2 and ·OH, while SO4•− was preferably for glycerol conversion to C3 products like glyceraldehyde and dihydroxyacetone with a total FE of about 80 %. Strikingly, the oxidative coupling of methane to ethanol was successfully achieved in our quasi-homogeneous system, yielding a remarkable production rate of 12.27 μmol h−1 and an impressive selectivity of 92.7 %. This study is anticipated to pave the way for novel approaches in steering solar-driven organic conversions by manipulating ROS to attain desired products and conversion ratios.

Influence of support properties on the activity of 2Cr-Fe/MgO-MO2 catalysts (M = Ce, Zr, CeZr and Si) for the dehydrogenation of n-octane with CO2

The influence of the support on catalytic activity and stability of supported 2Cr-Fe bimetallic catalysts for the CO2-assisted dehydrogenation (DH) of n-octane has been investigated. Four MgO modified supports viz; MgO-CeO2 (MgCe), MgO-ZrO2 (MgZr), MgO-CeO2-ZrO2 (MgCeZr) and MgO-SiO2 (MgSi) were synthesized by the sol-gel combustion technique. The supported catalysts were in turn prepared by vacuum impregnation and thereafter tested for the CO2-assisted DH of n-octane. The catalysts were characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), N2-physisorption, Raman spectroscopy, transmission electron microscopy (TEM), electron dispersive x-ray (EDX), temperature programmed desorption of CO2 (CO2-TPD), temperature programmed reduction and oxidation (H2-TPR and CO2-TPO), electron paramagnetic resonance (EPR) and thermal gravimetric analysis (TGA) techniques. Raman results showed that the CrOx is stabilized as mono- and/or polynuclear Cr(VI) species over the 2Cr-Fe/MgCe catalyst, which are reduced to lower oxidation state species during the DH reaction. The 2Cr-Fe/MgZr, 2Cr-Fe/MgCeZr and 2Cr-Fe/MgSi catalysts stabilized the CrOx as polymerized species, forming the more active Cr-O-Fe polymer units on the catalysts’ surface. XRD, TEM and EDX results showed that the ZrO2-containing supports have smaller particles and stabilized the active metal oxides in a more dispersed amorphous state. The CO2-TPO of the pre-reduced catalysts and EPR of the used catalysts indicated that the 2Cr-Fe/MgCeZr undergoes significant re-oxidation by CO2 during the catalytic process. The 2Cr-Fe/MgCe was the least active, while the 2Cr-Fe/MgZr catalyst showed the best performance and stability over three regeneration cycles. Selectivity to C8 products (octenes and aromatics) was found to strongly depend on the surface basicity of the catalysts. Deactivation of the catalysts was found to follow first order kinetics and coke deposition was identified as the major cause.

Electrocatalytic Glycerol Upgrading into Glyceric Acid on Ni3Sn Intermetallic Compound.

Electrochemical glycerol oxidation features an attractive approach of converting bulk chemicals into high-value products such as glyceric acid. Nonetheless, to date, the major product selectivity has mostly been limited as low-value C1 products such as formate, CO, and CO2, due to the fast cleavage of carbon-carbon (C-C) bonds during electro-oxidation. Herein, the study develops an atomically ordered Ni3Sn intermetallic compound catalyst, in which Sn atoms with low carbon-binding and high oxygen-binding capability allow to tune the adsorption of glycerol oxidation intermediates from multi-valent carbon binding to mono-valent carbon binding, as well as enhance *OH binding and subsequent nucleophilic attack. The Ni3Sn electrocatalyst exhibits one of the highest glycerol-to-glyceric acid performances, including a high glycerol conversion rate (1199µmol h-1) and glyceric acid selectivity (62 ± 3%), a long electrochemical stability of > 150 h, and the capability of direct conversion of crude glycerol (85% purity) into glyceric acid. The work features the rational design of highly ordered catalytic sites for tailoring intermediate binding and reaction pathways, thereby facilitating the efficient production of high-value chemical products.

W Single‐Atoms Anchored on Rutile TiO2 for Direct Methane Photocatalytic Conversion under Mild Conditions

Photo-driven direct CH4 conversion to value added liquid oxygenates attracts great attention for its enormous energy and environment benefits. However, because of the intrinsic inertness of CH4, realizing highly efficient direct CH4 conversion and prevent peroxidation remains a great challenge. Herein, a novel photocatalyst of rutile TiO2 supported W single-atoms was prepared for CH4 direct conversion to C1 products with 100% selectivity. The electron deficient property of the atomically-dispersed W active sites together with the photo-excited electron transferring from Ti to W can facilitate H2O2 adsorption and decomposition, and promote CH4 activation and conversion to varied products with a yield as high as 7 mmol gcat‐1 h‐1. This yield equaled to 238.5 mol molW‐1 h‐1, 82 times higher than that of the reported Cr single-atoms. In-situ ESR, FTIR and DFT simulation were combined to elucidate the CH4 conversion mechanism.

Nitrogen doping retrofits the coordination environment of copper single-atom catalysts for deep CO2 reduction

The electrocatalytic CO2 reduction reaction (CO2RR) represents an effective way to address energy crises and environmental issues by converting CO2 into valuable chemicals. Single-atom catalysts (SACs) can achieve excellent catalytic activity in CO2RR. However, the study of CO2RR on SACs still poses significant challenges, especially in terms of controlling the selectivity towards the deep product such as CH4 and CH3OH. Herein, we employ density functional theory (DFT) calculations to investigate the CO2RR on Cu SAC supported on N-doped graphene (Cu-N/C) and explore the role of N dopants on the CO2RR performance. Compared to Cu SACs supported on N-doped defective graphene with double vacancy (Cu-N/C-DV), Cu SACs supported on N-doped defective graphene with single vacancy (Cu-N/C-SV) can effectively convert CO2 into the deeply reduced C1 products, including CH4 and CH3OH, thus further indicating that Cu-N/C-SV has a stronger interaction with ∗CO, which is conducive to the deep reduction of ∗CO. Increasing the coordination number of N atoms or the proximity of doping site to the Cu active site can effectively enhance the stability of catalyst and promote the adsorption of ∗CO on Cu-N/C-SV. However, this also increases the free energy of the formation of ∗CHO intermediate. The results suggest that CuC3-Nm, which contains a N atom in the second coordination shell (meta-position) of Cu SACs, has the best electrocatalytic performance of CO2RR in terms of both selectivity and catalytic activity, not only contributing to an in-depth understanding of the reaction mechanism of CO2RR on SACs but also providing insights into the design of SACs for efficient CO2RR.

Ligand-tuning copper in coordination polymers for efficient electrochemical C–C coupling

Cu catalyses electrochemical CO2 reduction to valuable multicarbon products but understanding the structure-function relationship has remained elusive due to the active Cu sites being heterogenized and under dynamic re-construction during electrolysis. We herein coordinate Cu with six phenyl-1H-1,2,3-triazole derivatives to form stable coordination polymer catalysts with homogenized, single-site Cu active sites. Electronic structure modelling, X-ray absorption spectroscopy, and ultraviolet–visible spectroscopy show a widely tuneable Cu electronics by modulating the highest occupied molecular orbital energy of ligands. Using CO diffuse reflectance Fourier transform infrared spectroscopy, in-situ Raman spectroscopy, and density functional theory calculations, we find that the binding strength of *CO intermediate is positively correlated to highest occupied molecular orbital energies of the ligands. As a result, we enable a tuning of C–C coupling efficiency—a parameter we define to evaluate the efficiency of C2 production—in a broad range of 0.26 to 0.86. This work establishes a molecular platform that allows for studying structure-function relationships in CO2 electrolysis and devises new catalyst design strategies appliable to other electrocatalysis.

Dynamic Bubbling Balanced Proactive CO2 Capture and Reduction on a Triple-Phase Interface Nanoporous Electrocatalyst.

The formation and preservation of the active phase of the catalysts at the triple-phase interface during CO2 capture and reduction is essential for improving the conversion efficiency of CO2 electroreduction toward value-added chemicals and fuels under operational conditions. Designing such ideal catalysts that can mitigate parasitic hydrogen generation and prevent active phase degradation during the CO2 reduction reaction (CO2RR), however, remains a significant challenge. Herein, we developed an interfacial engineering strategy to build a new SnOx catalyst by invoking multiscale approaches. This catalyst features a hierarchically nanoporous structure coated with an organic F-monolayer that modifies the triple-phase interface in aqueous electrolytes, substantially reducing competing hydrogen generation (less than 5%) and enhancing CO2RR selectivity (∼90%). This rationally designed triple-phase interface overcomes the issue of limited CO2 solubility in aqueous electrolytes via proactive CO2 capture and reduction. Concurrently, we utilized pulsed square-wave potentials to dynamically recover the active phase for the CO2RR to regulate the production of C1 products such as formate and carbon monoxide (CO). This protocol ensures profoundly enhanced CO2RR selectivity (∼90%) compared with constant potential (∼70%) applied at -0.8 V (V vs RHE). We further achieved a mechanistic understanding of the CO2 capture and reduction processes under pulsed square-wave potentials via in situ Raman spectroscopy, thereby observing the potential-dependent intensity of Raman vibrational modes of the active phase and CO2RR intermediates. This work will inspire material design strategies by leveraging triple-phase interface engineering for emerging electrochemical processes, as technology moves toward electrification and decarbonization.

A First-Principles Study on the Reaction Mechanisms of Electrochemical CO2 Reduction to C1 and C2 Products on Cu(110)

The mechanism of the electrochemical CO2 reduction reaction on a Cu(110) surface has yet to be fully revealed. In this work, based on first-principles calculations, we investigate the mechanisms of the CO2 reduction reaction to produce C1 (including one C atom) and C2 (including two C atoms) products on a Cu(110) surface. The results show that CH4 and C2H5OH are the main C1 and C2 products on the Cu(110) surface, respectively. CH4 is produced along the pathway CO2 → COOH* → CO* → CHO* → CH2O* → CH3O* → CH4. C2H5OH is produced via the C-C coupling pathway between CO* and CH2O* intermediates, which is the key reaction step. This is because CO* and CH2O* coupling to CO-CH2O* has the lowest barrier among the CHxO* (x = 0–2) coupling pathways. Therefore, it is the most likely C-C coupling pathway. Further, CO-CH2O* is gradually hydrogenated to C2H5OH along the following pathway: CO-CH2O* → CHO-CH2O* → CHOH-CH2* → CH2OH-CH2* → CH2OH-CH3* → C2H5OH.

Real‐Time Product Detection during CO2 Electroreduction on SCILL‐Modified Cu Catalysts

AbstractModifying the chemical environment of active surfaces with ionic liquids (IL) is an emerging strategy for tailoring novel electrocatalytic systems, including carbon dioxide reduction (CO2RR). Although copper (Cu) catalysts have recently gained more attention in this field, their modification with ILs is yet to be investigated. This work tested a range of common hydrophobic ILs impregnated into carbon‐supported Cu catalysts, following the “solid catalyst with ionic liquid layer” (SCILL) approach. The latter was used to showcase the applicability of real‐time product detection for CO2RR employing electrochemical mass spectrometry. The observed patterns of C1 to C3 product selectivity offered valuable insights into the intricate reaction mechanism. In addition, increasing the size of the IL cation showed an opposite and significant effect on the reaction selectivity. The obtained qualitative results were partially compared with conventional long‐term experiments.

Facile Synthesis of Silanol Group Rich Sn‐Beta for Highly Efficient Isomerization of Glucose to Fructose

AbstractThe isomerization of glucose to fructose is an important process in the conversion of biomass into valuable fuels and chemicals. Development of efficient catalyst for this reaction has attracted much attention. In this study, Sn‐Beta zeolites with rich silanols were synthesized for glucose isomerization by solid‐state ion‐exchange method, where Si‐Beta zeolites with different amounts of silanols were applied as the precursors. It is confirmed that open Sn sites show much higher catalytic performance than closed Sn sites for glucose isomerization (about 2.1 times). The silanol amount in Si‐Beta not only affects the formation of framework Sn sites in Sn‐Beta but also influences the isomerization reaction. More silanols in the catalyst can promote the 1,2‐H shift in isomerization and reduce the side reactions of formation of mannose and C3 products. Over 3Sn‐Beta‐3h with rich silanols, 64 % of fructose yield was obtained. Furthermore, the prepared Sn‐Beta catalyst is stable and recyclable. High fructose yield and facile synthesis method of Sn‐Beta reported in this work will contribute to the development of biomass and sugar industry.

Delocalized Orbitals over Metal Clusters and Organic Linkers Enable Boosted Charge Transfer in Metal-Organic Framework for Overall CO2 Photoreduction.

The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi-electron transfer process. Herein, taking metal-organic framework (MOF, PFC-98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC-6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge-separated (ICS) state, prolonging the excited state lifetime and further inhibiting the electron-hole recombination. The presence of ICS state prolongs the excited state lifetime and further inhibits the electron-hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi-electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.

Oxygenate-induced structural evolution of high-entropy electrocatalysts for multifunctional alcohol electrooxidation integrated with hydrogen production

High-entropy compounds have been emerging as promising candidates for electrolysis, yet their controllable electrosynthesis strategy remains a formidable challenge because of the ambiguous ionic interaction and codeposition mechanism. Herein, we report a oxygenates directionally induced electrodeposition strategy to construct high-entropy materials with amorphous features, on which the structural evolution from high-entropy phosphide to oxide is confirmed by introducing vanadate, thus realizing the simultaneous optimization of composition and structure. The representative P-CoNiMnWVOx shows excellent bifunctional catalytic performance toward alkaline hydrogen evolution reaction and ethanol oxidation reaction (EOR), with small potentials of -168 mV and 1.38 V at 100 mA cm-2, respectively. In situ spectroscopy illustrates that the electrochemical reconstruction of P-CoNiMnWVOx induces abundant Co-O species as the main catalytic active species for EOR and follows the conversion pathway of the C2 product. Theoretical calculations reveal the optimized electronic structure and adsorption free energy of reaction intermediates on P-CoNiMnWVOx, thereby resulting in a facilitated kinetic process. A membrane-free electrolyzer delivers both high Faradaic efficiencies of acetate and H2 over 95% and superior stability at100 mA cm-2 during 120 h electrolysis. In addition, the unique composition and structural advantages endow P-CoNiMnWVOx with multifunctional catalytic activity and realize multipathway electrosynthesis of formate-coupled hydrogen production.

Delocalized Orbitals Over Metal Clusters and Organic Linkers Enable Boosted Charge Transfer in Metal‐Organic Framework for Overall CO2 Photoreduction

The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi‐electron transfer process. Herein, taking metal‐organic framework (PFC‐98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC‐6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge‐separated state (ICS), prolonging the excited state lifetime and further inhibiting the electron‐hole recombination. The presence of an internal charge‐separated state (ICS) prolongs the excited state lifetime and further inhibits the electron‐hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi‐electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.

Ultrafast photochemistry and electron diffraction for cyclobutanone in the S2 state: Surface hopping with time-dependent density functional theory.

We simulate the photodynamics of gas-phase cyclobutanone excited to the S2 state using fewest switches surface hopping (FSSH) dynamics powered by time-dependent density functional theory (TDDFT). We predict a total photoproduct yield of 8%, with a C3:C2 product ratio of 0 trajectories to 8 trajectories. One primary S2 → S1 conical intersection is identified involving the compression of an α-carbon-carbon-hydrogen bond angle. Excited state lifetimes computed with respect to electronic state populations were found to be 3.96ps (S2 → S1) and 498fs (S1 → S0). We also generate time-resolved difference pair distribution functions (ΔPDFs) from our TDDFT-FSSH dynamics results in order to generate direct comparisons with ultrafast electron diffraction experiment observables. Global and target analysis of time-resolved ΔPDFs produced a distinct set of lifetimes: (i) a 0.548ps decay and (ii) a 1.69ps decay, both resembling the S2 minimum, as well as (iii) a long decay that resembles the S1 minimum geometry and the fully separated C2 products. Finally, we contextualize our results by considering the impact of the most likely sources of significant errors.

Confined CuⅠ sites in partially electro-reduced 2D conductive Cu-MOF film for boosting CO2 electrocatalysis to C2 products

Cu-based catalysts, especially co-sites of Cu0 and CuⅠ, are the best competitors for electrochemical CO2 fixation to produce multi-carbon (C2 + ) products. However, it is challenging to construct highly stable CuⅠ sites due to the changeability of its valence state and electronic structure in the electroreduction process, and the mechanism is also elusive. Herein, a 2D conductive CuⅡ-MOF film (CuⅡHHTP@Cu0) is prepared on Cu (100) foil by in-situ electrochemical assembly. After pre-reduction, the in-situ produced Cu2O clusters are confined in the cavities of the film created by the local breaking of the MOF framework to construct a unique CuⅠ-CuⅡHHTP@Cu0 catalyst, so that a novel strategy is proposed to stablize highly dispersed CuⅠ sites during electrochemical reduction, thus protecting the Cu2O clusters from further reduction and ensuring the coexistence of CuⅠ (111)-Cu0 (100) sites. As such, the current density of CO2 electrochemical reduction catalyzed by this catalyst exceeds 300 mA cm−2, the duration overs 50 h, and the C2 selectivity achieves 72.6 %. In-situ spectroscopy and theoretical calculations reveal that the optimized microenvironment of the CuⅠ (111) sites reduces the energy barrier of *OCCOH coupling, and Cu0 (100) sites increase the coverage of *CO, thus boosting the production of C2 products.

Correction of the cracking mechanism ratio in catalytic cracking process to characterize the thermal cracking reaction and realize highly sensitive identification of catalysts

AbstractIn this work, we have specially carried out the catalytic cracking experiments of heavy distillate oil in the high temperature range of 500~700°C. The composition of dry gas generated in the catalytic cracking process was analyzed, with emphasis on the variation of yield of C1 and C2 products. Two cracking mechanism ratios (CMRs) were redefined by replacing the (C1 + C2) products in the traditional definition of CMR with CH4, and the feasibility of using them to characterize the thermal cracking reaction in the catalytic cracking process in the high temperature range was investigated. The results showed that CH4 was more sensitive to temperature than (C1 + C2) and it was feasible and more accurate to use CH4 instead of (C1 + C2) corrected R3 to characterize the thermal cracking reaction in the catalytic cracking process in the high temperature range. In addition, it was found that the corrected R3 had the effect of distinguishing and identifying catalysts.

Landscape and paleoenvironmental change in stream valleys of the Central Great Plains, North America, during Marine Isotope Stage 3 (ca. 59–27 ka)

Recent studies of late Quaternary landscape evolution in stream valleys throughout the central Great Plains of North America have identified thick packages of MIS 3-age alluvium and colluvium beneath terraces, alluvial fans, and footslopes. Here, we review and build on these studies to highlight the geomorphic history of river systems in the Central Plains during MIS 3 and reconstruct the paleoclimatic conditions and vegetation communities that existed in the region at that time.A suite of 50 radiocarbon and optically stimulated luminescence ages indicate that late MIS 3 was a period of widespread landscape stability and soil development in the Central Plains. In general, river systems were actively aggrading during early MIS 3, but aggradation slowed after ca. 40 ka, allowing soils to develop until ca. 30–27 ka. In some river valleys, a second pulse of aggradation occurred shortly after that time followed by a period of landscape stability and pedogenesis during early MIS 2 (ca. 24–19 ka). Evidence for widespread landscape stability in stream valleys implies that high magnitude flooding was minimal. Atmospheric circulation patterns that favor these conditions include zonal airflow that inhibits incursions of moist, maritime air from the Gulf of Mexico.Paleoenvironmental conditions during late MIS 3 were reconstructed using the stable carbon, oxygen, and hydrogen isotopic composition of pedogenic phyllosilicates, carbonates, and organic matter. Estimated paleotemperatures ranged from 6 to 9 °C ± 3 °C and are approximately 4–7 °C lower than modern mean annual temperature. The estimated δ18O values of soil water from phyllosilicates range from −10.6‰ to −9.6‰. These estimates are lower (18O-depleted) by about 1.5–3‰ relative to modern meteoric δ18O values and we estimate that the δ18O of paleoprecipitation was likely 18O-depleted by up to 8.5‰ relative to modern values. Our estimated δ18O values for soil waters in the Central Plains during late MIS 3 can be explained by climatic conditions characterized by 1) cooler temperatures, 2) precipitation being sourced primarily from Pacific/Arctic air masses, 3) seasonal changes in precipitation patterns (i.e., predominantly winter precipitation), or 4) a combination of the above. δ13C values indicate the presence of a notable proportion of C4 vegetation in the Central Plains during late MIS 3. We suggest that C4 productivity was likely favored at that time by a low atmospheric CO2 environment that had sufficiently warm temperatures and effective precipitation during the growing season.

Cu Based Dilute Alloys for Tuning the C2+ Selectivity of Electrochemical CO2 Reduction.

Electrochemical CO2 reduction is a promising technology for replacing fossil fuel feedstocks in the chemical industry but further improvements in catalyst selectivity need to be made. So far, only copper-based catalysts have shown efficient conversion of CO2 into the desired multi-carbon (C2+) products. This work explores Cu-based dilute alloys to systematically tune the energy landscape of CO2 electrolysis toward C2+ products. Selection of the dilute alloy components is guided by grand canonical density functional theory simulations using the calculated binding energies of the reaction intermediates CO*, CHO*, and OCCO* dimer as descriptors for the selectivity toward C2+ products. A physical vapor deposition catalyst testing platform is employed to isolate the effect of alloy composition on the C2+/C1 product branching ratio without interference from catalyst morphology or catalyst integration. Six dilute alloy catalysts are prepared and tested with respect to their C2+/C1 product ratio using different electrolyzer environments including selected tests in a 100-cm2 electrolyzer. Consistent with theory, CuAl, CuB, CuGa and especially CuSc show increased selectivity toward C2+ products by making CO dimerization energetically more favorable on the dominant Cu facets, demonstrating the power of using the dilute alloy approach to tune the selectivity of CO2 electrolysis.

Hydrochar from Pine Needles as a Green Alternative for Catalytic Electrodes in Energy Applications.

Hydrothermal carbonization (HTC) serves as a sustainable method to transform pine needle waste into nitrogen-doped (N-doped) hydrochars. The primary focus is on evaluating these hydrochars as catalytic electrodes for the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR), which are pivotal processes with significant environmental implications. Hydrochars were synthesized by varying the parameters such as nitrogen loading, temperature, and residence time. These materials were then thoroughly characterized using diverse analytical techniques, including elemental analysis, density measurements, BET surface area analysis, and spectroscopies like Raman, FTIR, and XPS, along with optical and scanning electron microscopies. The subsequent electrochemical assessment involved preparing electrocatalytic inks by combining hydrochars with an anion exchange ionomer (AEI) to leverage their synergistic effects. To the best of our knowledge, there are no previous reports on catalytic electrodes that simultaneously incorporate both a hydrochar and AEI. Evaluation metrics such as current densities, onset and half-wave potentials, and Koutecky-Levich and Tafel plots provided insights into their electrocatalytic performances. Notably, hydrochars synthesized at 230 °C exhibited an onset potential of 0.92 V vs. RHE, marking the highest reported value for a hydrochar. They also facilitated the exchange of four electrons at 0.26 V vs. RHE in the ORR. Additionally, the CO2RR yielded valuable C2 products like acetaldehyde and acetate. These findings highlight the remarkable electrocatalytic activity of the optimized hydrochars, which could be attributed, at least in part, to their optimal porosity.

Non-adiabatic dynamics of photoexcited cyclobutanone: Predicting structural measurements from trajectory surface hopping with XMS-CASPT2 simulations.

Over the years, theoretical calculations and scalable computer simulations have complemented ultrafast experiments, as they offer the advantage of overcoming experimental restrictions and having access to the whole dynamics. This synergy between theory and experiment promises to yield a deeper understanding of photochemical processes, offering valuable insights into the behavior of complex systems at the molecular level. However, the ability of theoretical models to predict ultrafast experimental outcomes has remained largely unexplored. In this work, we aim to predict the electron diffraction signals of an upcoming ultrafast photochemical experiment using high-level electronic structure calculations and non-adiabatic dynamics simulations. In particular, we perform trajectory surface hopping with extended multi-state complete active space with second order perturbation simulations for understanding the photodissociation of cyclobutanone (CB) upon excitation at 200nm. Spin-orbit couplings are considered for investigating the role of triplet states. Our simulations capture the bond cleavage after ultrafast relaxation from the 3s Rydberg state, leading to the formation of the previously observed primary photoproducts: CO + cyclopropane/propene (C3 products), ketene, and ethene (C2 products). The ratio of the C3:C2 products is found to be about 1:1. Within 700fs, the majority of trajectories transition to their electronic ground state, with a small fraction conserving the initial cyclobutanone ring structure. We found a minimal influence of triplet states during the early stages of the dynamics, with their significance increasing at later times. We simulate MeV-ultrafast electron diffraction (UED) patterns from our trajectory results, linking the observed features with specific photoproducts and the underlying structural dynamics. Our analysis reveals highly intense features in the UED signals corresponding to the photochemical processes of CB. These features offer valuable insights into the experimental monitoring of ring opening dynamics and the formation of C3 and C2 photoproducts.