Coevolution Research Articles

Adjustment of charge transfer behavior for layered photocatalysts through fabricating face-to-face 2D/2D S-scheme heterojunction toward efficient CO2 reduction

It is a challenging issue to improve charge transfer and separation between neighboring layers of for the layered photocatalysts, because the photogenerated charges are more inclined to migrate within the layer due to their inherent anisotropy. Herein, a new 2D/2D heterojunction is fabricated by implanting Bi2O2S nanoplates into the polymeric carbon nitride (PCN) nanosheets, in which the large area of tightly face-to-face coupling architecture is formed between them that significantly improves the photophysical, photoelectrochemical and electrochemical properties relative to PCN. It is important that this unique architecture induces a strong built-in electric field and gives rise to a S-scheme charge transfer pathway between Bi2O2S and PCN, which effectively conquers the restriction of charge transfer between neighboring layers inside heterojunction, thus significantly improving the whole separation efficiency of photogenerated carriers of the 2D/2D Bi2O2S/PCN heterojunction. As a consequence, the optimal Bi2O2S/PCN-20 heterojunction achieves an average CO evolution rate of 2.61 and 2.15 times that of PCN and Bi2O2S for photocatalytic CO2 reduction reaction, respectively, and exhibits the superior reusability and stability. This work opens a viable design avenue for controlling the charge transfer behavior of anisotropic layered photocatalysts.

In situ construction of S-scheme heterojunctions between BiOCl and Bi-MOF for enhanced photocatalytic CO2 reduction and pollutant degradation

Recently, photocatalytic technology has been widely used as a sustainable method to address environmental pollution issues. Herein, BiOCl/Bi-MOF (BOC/Bi-MOF) based semiconductor photocatalysts with S-scheme heterojunction were fabricated by an in situ growth method, and the photocatalytic activity of the materials was explored for CO2 reduction and pollutant degradation. As confirmed by density functional theory calculations and physiochemical characterizations, the established S-scheme heterojunction confers enhanced carrier separation efficiency and retention of redox capability to the BOC/Bi-MOF. Through an improved combination of charge separation and surface reactions, the prepared BOC/Bi-MOF efficiently reduces CO2 solely to CO. The heterojunction as catalyst is more durable and effective than any of its single component. The CO evolution rate of the optimized composite catalyst was 7.66 and 33.10 times of those of BiOCl and Bi-MOF, respectively. In addition, BOC/Bi-MOF exhibits a high efficiency in the photocatalytic degradation of the pollutant rhodamine B (RhB) in aqueous environments, and the pollutant was completely removed within 20 min. Due to the generation of interfacial potential differences, the internal electric field (IEF) generation at heterogeneous interfaces facilitates the separation and transfer of photogenic charges. This work demonstrated a practical and effective route for in situ growth of S-scheme heterojunctions with high efficiencies in CO2 reduction and RhB degradation.

Carbon dioxide suppresses filamentous growth in the human fungal pathogen Candida tropicalis.

A striking characteristic of the human fungal pathogen Candida albicans is its ability to switch between budding yeast morphology and the filamentous form, facilitating its adaptation to changing host environments. The filamentous growth of C. albicans is mediated by various environmental factors, such as carbon dioxide (CO2), N-acetylglucosamine (GlcNAc), serum, and high temperature. Despite extensive studies in C. albicans, the regulatory mechanism of filamentation in Candida tropicalis, a fungal species that is closely related to C. albicans, has not been well characterized. In this study, we reveal opposite roles of CO2 in regulating filamentation among Candida species: CO2 promotes filamentous growth in C. albicans and Candida dubliniensis, whereas it inhibits filamentation in C. tropicalis. Despite the critical role of the canonical cAMP pathway in filamentation, it is dispensable in CO2-regulated filamentation in C. tropicalis. A CO2-specific signaling is involved in the regulation of filamentous growth in C. tropicalis. Additionally, we identify two key elements involved in CO2 sensing in C. tropicalis: a single carbonic anhydrase (CA) Nce103 and the bZIP transcription factor Rca1. Both Nce103 and Rca1 are important for cellular growth in ambient air and negatively regulate filamentous development in response to CO2 in C. tropicalis. These findings reveal a distinct mechanism underlying CO2-regulated filamentation in C. tropicalis, contributing to a deeper understanding of its unique survival strategies in diverse environmental niches and providing new insights into the adaptive evolution of CO2 sensing mechanisms among various fungal pathogens.

Revealing the CO Tolerance Mechanism in Acidic Hydrogen Oxidation Reactions on Platinum‐Based Catalyst Surfaces

AbstractThe presence of trace CO impurity gas in hydrogen fuel can rapidly deactivate platinum‐based hydrogen oxidation reaction (HOR) catalysts due to poisoning effects, yet the precise CO tolerance mechanism remains debated. Our designed Au@PtX bifunctional core–shell nanocatalysts exhibit excellent performance of CO tolerance in acidic solution during HOR and possess exceptional Raman spectroscopy enhancement. Through capturing and analyzing in situ Raman spectroscopy evidences on *OH, metal‐O species and *CO evolution under 0.3 V, we confirm that oxygen‐containing species on PtRu and PtSn catalysts promote the oxidation and desorption of *CO. While Ru enhances *CO adsorption on Pt, the primary CO tolerance performance of PtRu arises from *CO oxidation via a bifunctional pathway. Additionally, electronic structure of Sn reduces *CO adsorption on Pt sites, complementing the bifunctional mechanism to further enhance the CO tolerance performance of PtSn. These discoveries significantly deepen our understanding of the anti‐poisoning mechanism of Pt‐based catalysts in the HOR process and offer valuable insights for rational catalyst design.

Revealing the CO Tolerance Mechanism in Acidic Hydrogen Oxidation Reactions on Platinum-Based Catalyst Surfaces.

The presence of trace CO impurity gas in hydrogen fuel can rapidly deactivate platinum-based hydrogen oxidation reaction (HOR) catalysts due to poisoning effects, yet the precise CO tolerance mechanism remains debated. Our designed Au@PtX bifunctional core-shell nanocatalysts exhibit excellent performance of CO tolerance in acidic solution during HOR and possess exceptional Raman spectroscopy enhancement. Through capturing and analyzing in situ Raman spectroscopy evidences on *OH, metal-O species and *CO evolution under 0.3 V, we confirm that oxygen-containing species on PtRu and PtSn catalysts promote the oxidation and desorption of *CO. While Ru enhances *CO adsorption on Pt, the primary CO tolerance performance of PtRu arises from *CO oxidation via a bifunctional pathway. Additionally, electronic structure of Sn reduces *CO adsorption on Pt sites, complementing the bifunctional mechanism to further enhance the CO tolerance performance of PtSn. These discoveries significantly deepen our understanding of the anti-poisoning mechanism of Pt-based catalysts in the HOR process and offer valuable insights for rational catalyst design.

Optimizing thermal and thermal-alkaline pretreatments for polylactic acid biodegradation by Amycolatopsis orientalis and Amycolatopsis thailandensis.

Environmental pollution from packaging, has led to a need for sustainable alternatives. This study investigates the biodegradation of polylactic acid (PLA) by Amycolatopsis orientalis and Amycolatopsis thailandensis after thermal and thermal-alkaline pretreatments. The biodegradation was assessed based on weight loss, CO2 evolution, carbon balance analysis and scanning electron microscopy (SEM). The analysis showed that pretreatment at 37 °C for 8 h provided effective enhancement of the biodegradation performance. Combining thermal pretreatment with alkaline conditions led to chemical degradation of PLA, but is less suitable as a pretreatment for biodegradation. It was also demonstrated that the mineralization rate over a two-week period was higher following thermal than thermal-alkaline pretreatment. SEM confirmed improved biodegradation as illustrated by increased surface roughness. These findings suggest that thermal pretreatment at 37 °C for 8 h is the most effective strategy for enhancing PLA biodegradation by Amycolatopsis spp., promoting a sustainable approach to plastic waste management.

Solid solution characteristic and magnetic evolutions of nanostructured cobalt-based Co–Fe–Zr–Nb–B alloy

Solid solution characteristic and magnetic evolutions of nanostructured cobalt-based Co–Fe–Zr–Nb–B alloy

Dynamic behavior and permeability evolution of CO2 hydrates during dissociation by depressurization: Insights from low-field nuclear magnetic resonance

Dynamic behavior and permeability evolution of CO2 hydrates during dissociation by depressurization: Insights from low-field nuclear magnetic resonance

1D Covalent Organic Frameworks with Tunable Dual-Cobalt Synergistic Sites for Efficient CO2 Photoreduction.

Diatomic catalysts enhance photocatalytic CO2 reduction through synergistic effects. However, precisely regulating the distance between two catalytic centers to achieve synergistic catalysis poses significant challenges. In this study, a series of one-dimensional (1D) covalent organic frameworks (COFs) are designed with adjustable micropores to facilitate efficient CO2 photoreduction. CO2 molecules are anchored between dual-cobalt centers within micropores, thus effectively reducing their activation energy and initiating the photocatalytic process. Additionally, the formation of *COOH intermediates is significantly influenced by the coordination microenvironment around dual-cobalt sites. Notably, COF-Co-N4 exhibited remarkable CO2 photoreduction activity with a CO evolution rate of 110.3 µmol·g-1·h-1, which surpasses most of previously reported single-atom-site photocatalysts. Comprehensive characterization and density functional theory (DFT) calculations revealed that 1D COFs with dual-cobalt sites possess the ability to anchor CO2 molecules, thereby enhancing the efficacy of synergistic catalysis. Simultaneously, COF-Co-N4 with quadruple nitrogen coordination significantly reduced the energy barrier of crucial *COOH intermediate, facilitating efficient photocatalytic CO2 reduction. This study meticulously modulated the coordination microenvironment surrounding dual-cobalt synergistic sites, providing new insight into the design of high-performance photocatalysts.

Visible-Light-Driven CO₂ Reduction Using Imidazole-Based Metal-Organic Frameworks as Heterogeneous Photocatalysts.

The development of robust, efficient, and cost-effective heterogeneous photocatalysts for visible light-driven CO2 reduction continues to be a significant challenge in the quest for sustainable energy solutions. As a result, increasing attention is being directed towards the exploration of high-performance photocatalysts capable of converting CO2 into chemical feedstocks. Imidazolate Frameworks Potsdam (IFPs)can be a promising candidate for CO2 photoreduction due to their ease of synthesis, use of low-cost, earth-abundant metals, and high chemical and thermal stability. Herein, we report the synthesis of Zn(II)- and Co(II)-based IFPs, specifically IFP-1(Zn) and IFP-5(Co), for photocatalytic CO2 reduction. Moreover, we demonstrate the enhanced photocatalytic activity of redox-innocent Zn-based IFP-1 by partially substituting Zn(II) with redox-active Co(II) in IFP-1(Zn), resulting in the formation of a bimetallic photocatalyst, IFP-1(Zn/Co). The IFP-1(Zn/Co) exhibited significantly improved CO evolution (637 μmol g-1 in 1 hour), compared to the pristine IFP-1(Zn) (29 μmol g-1). Among all the prepared photocatalysts, IFP-5(Co) outperformed both the systems, achieving a CO evolution of 1174 μmol g-1 within 1 hour, due to the presence of catalytic cobalt sites. In addition, through the combination of photophysical and electrochemical studies, along with DFT calculations, we have proposed a plausible mechanism for the photocatalytic CO2 reduction.

Biochars Induced Changes in CO2 Evolution and Biochemical Properties of an Alkaline Subtropical soil

Biochars Induced Changes in CO2 Evolution and Biochemical Properties of an Alkaline Subtropical soil

Zn and Cl Coregulated MXene Catalyst Enhances Li-CO2 Battery Reversibility.

MXenes are promising cathodes for Li-CO2 batteries owing to their high electrical conductivity and efficient CO2 activation function. However, the effects of adsorption and electronic structures of MXene on the full life cycle of Li-CO2 batteries have been rarely investigated. Here, we employ a coregulation approach to enhance the adsorption-decomposition of lithium carbonate (Li2CO3) by introducing Zn and Cl surface groups onto the Ti3C2 MXene (Zn-Ti3C2Cl2) catalyst. The incorporation of Cl surface groups enhances Li2CO3 adsorption on the MXene catalyst surface, resulting in the formation of small-sized and uniform Li2CO3. Additionally, the introduction of Zn shifts the d-band centers of titanium and promotes CO2 evolution reaction (CO2ER) activity, thereby facilitating the decomposition of discharge products. As a result, the Li-CO2 battery based on the Zn-Ti3C2Cl2 catalyst exhibits an ultralow overpotential (0.72 V) at 200 mA g-1 and stable cycling for up to 1500 h. This work validates the efficacy of promoting reversibility in Li-CO2 batteries by adjusting the adsorption-decomposition process.

CO-to-H2 conversion factor and grain size distribution through the analysis of αCO–qPAH relation

Abstract The CO-to-H2 conversion factor (αCO) is expected to vary with dust abundance and grain size distribution through the efficiency of shielding gas from CO-dissociation radiation. We present a comprehensive analysis of αCO and grain size distribution for nearby galaxies, using the PAH fraction (qPAH) as an observable proxy of grain size distribution. We adopt the resolved observations at 2 kpc resolution in 42 nearby galaxies, where αCO is derived from measured metallicity and surface densities of dust and H i assuming a fixed dust-to-metals ratio. We use an analytical model for the evolution of H2 and CO, in which the evolution of grain size distribution is controlled by the dense gas fraction (η). We find that the observed level of qPAH is consistent with the diffuse-gas-dominated model (η = 0.2) where dust shattering is more efficient. Meanwhile, the slight decreasing trend of observed qPAH with metallicity is more consistent with high-η predictions, likely due to the more efficient loss of PAHs by coagulation. We discuss how grain size distribution (indicated by qPAH) and metallicity impact αCO; we however did not obtain conclusive evidence that the grain size distribution affects αCO. Observations and model predictions show similar anti-correlation between αCO and 12+log(O/H). Meanwhile, there is a considerable difference in how resolved αCO behaves with qPAH. The observed αCO has a positive correlation with qPAH, while the model-predicted αCO does not have a definite correlation with qPAH. This difference is likely due to the limitation of one-zone treatment in the model.

A simple model and rules for the evolution of microbial mutualistic symbiosis with positive fitness feedbacks

The evolution of microbe-microbe mutualistic symbiosis is considered to be promoted by repeated exchanges of fitness benefits, which can generate positive fitness feedbacks ('partner fidelity feedback') between species. However, previous evolutionary models for mutualism have not captured feedback dynamics or coupling of fitness between species. Here, a simple population model is developed to understand the evolution of mutualistic symbiosis in which two microbial species (host and symbiont) continuously grow and exchange fitness benefits to generate feedback dynamics but do not strictly control each other. The assumption that individual microbes provide constant amounts of resources, which are equally divided among interacting partner individual, enables us to reveal a simple rule for the evolution of costly mutualism with positive fitness feedbacks: the product of the benefit-to-cost ratios for each species exceeds one. When this condition holds, high cooperative investment levels are favored in both species regardless of the amount invested by each partner. The model is then extended to examine how symbiont mutation, immigration, or switching affects the spread of selfish or cooperative symbionts, which decrease and increase their investment levels, respectively. In particular, when a host associates with numerous symbionts without enforcement, neither mutation nor immigration but rather random switching would allow the spread of cooperative symbionts. Examples using symbiont switching for evolution would include large ciliates hosting numerous intracellular endosymbionts. The simple model and rules would provide a basis for understanding the evolution of microbe-microbe mutualistic symbiosis with positive fitness feedbacks and without enforcement mechanisms.

Environmental Changes Recorded in Sedimentary Rocks in the Clay-Sulfate Transition Region in Gale Crater, Mars: Results From the Sample Analysis at Mars-Evolved Gas Analysis Instrument Onboard the Mars Science Laboratory Curiosity Rover.

The Curiosity rover explored the region between the orbitally defined phyllosilicate-bearing Glen Torridon trough and the overlying layered sulfate-bearing unit, called the "clay-sulfate transition region." Samples were drilled from the top of the fluviolacustrine Glasgow member of the Carolyn Shoemaker formation (CSf) to the eolian Contigo member of the Mirador formation (MIf) to assess in situ mineralogical changes with stratigraphic position. The Sample Analysis at Mars-Evolved Gas Analysis (SAM-EGA) instrument analyzed drilled samples within this region to constrain their volatile chemistry and mineralogy. Evolved H2O consistent with nontronite was present in samples drilled in the Glasgow and Mercou members of the CSf but was generally absent in stratigraphically higher samples. SO2 peaks consistent with Fe sulfate were detected in all samples, and SO2 evolutions consistent with Mg sulfate were observed in most samples. CO2 and CO evolutions were variable between samples and suggest contributions from adsorbed CO2, carbonates, simple organic salts, and instrument background. The lack of NO and O2 in the data suggest that oxychlorines and nitrates were absent or sparse, and evolved HCl was consistent with the presence of chlorides in all samples. The combined rover data sets suggest that sediments in the upper CSf and MIf may represent similar source material and were deposited in lacustrine and eolian environments, respectively. Rocks were subsequently altered in briny solutions with variable chemical compositions that resulted in the precipitation of sulfates, carbonates, and chlorides. The results suggest that the clay-sulfate transition records progressivelydrier surface depositional environments and saline diagenetic fluid, potentially impacting habitability.

Study on the reaction mechanism and kinetics of limestone hydrogenation by micro fluidized bed: Effect of H2 concentration and natural limestone

Limestone decomposition is the first step in cement production, which produces a significant amount of CO2 and poses a significant challenge to achieve carbon neutrality. Hydrogenation of limestone can produce CO or CH4 instead of CO2, which can be considered as a new way of carbon capture, making it a promising method for carbon emission reduction. In this work, pure CaCO3 and several natural limestone samples were hydrolyzed under varying H2 concentration using a micro fluidized bed (MFB) reactor combined with online mass spectrometry to reveal the mechanism and kinetics of limestone hydrogenation.The main gases produced by hydrogenation at 1 atm are CO and CO2. The CO2 comes from the calcination of CaCO3. The CO comes from 2 steps: the first step is the in-situ hydrogenation of CaCO3 and the second step is the Reverse Water Gas Shift (RWGS) reaction. The activation energy (Ea) of CO2 formation in H2 atmosphere is lower than in Ar atmosphere. However, there is no obvious effect of different H2 concentrations on the Ea of CO2 formation. The Ea of CO in situ formation is 72.70 KJ/mol, 54.53 KJ/mol, 71.34 KJ/mol and 60.29 KJ/mol in 10%, 30%, 50% and 70% H2 atmosphere, respectively. The H2 concentration also has no significant effect on the in-situ CO evolution. However, the H2 concentration can affect the Ea of CO produced by RWGS. The Ea is 75.67 KJ/mol, 167.59 KJ/mol and 221.47 KJ/mol in 10%, 30% and 50% H2 atmosphere, and this reaction doesn't occur in 70% H2 atmosphere. Compared with the pure CaCO3, the hydrogenation of limestone can produce more CO and less CO2. In limestone, impurity elements are the main factor affecting the reaction kinetics. Transition metals can increase the rate of CO2 production, but have no apparent effect on CO. The CO2 yield of high impurity limestone is higher than that of limestone with low impurities. Transition metals can also reduce the Ea of CO2 formation and the RWGS reaction. In the 50% H2 atmosphere, the Ea of CO2 formation is 88.87 KJ/mol and the Ea of CO from RWGS is 137.60 KJ/mol. However, under the same conditions, the Ea of pure CaCO3 is 126.91 KJ/mol and 221.47 KJ/mol.

A phase-diagram-formulated EOS and fluid-solid coupling analysis for eco-friendly blasting of carbon dioxide phase transition

The Carbon dioxide (CO2) phase transition blasting is a state-of-the-art technology in fields of geotechnical, geological, and mining engineering, due to its advantages of high safety, environmental friendliness (Non-toxic and smoke-free), and cost-effective design benefited from the low-temperature characteristics. However, the evolution mechanism of CO2 within the pressure vessel before the blasting is still not clearly revealed. To address this issue, a phase-diagram-formulated Equation of State (EOS) is proposed to describe the phase evolution and mechanical behaviors of CO2. Furthermore, a fluid-solid coupling simulation model is established using the Euler grid-based Finite Element Method (FEM). The simulation model is validated through CO2 phase transition blasting experiments and then used for the mechanism analysis. The results reveal that the initial rapid rise, further slow increase, and extremely rapid decline of the pressure evolution in the vessel are dominated by the combination of heat absorption and external work, the phase transition of CO2, and the failure of the rupture disc, respectively. In addition, the influence laws of combustion agent energy, environment temperature and rupture disc strength on the blasting are systematically investigated. The final conclusions may provide useful insights for the design of CO2 phase transition blasting and the development of eco-friendly blasting technologies.

Isomeric Covalent Organic Frameworks for High-Efficiency Photocatalytic CO2 Reduction: Substituent Position Effect.

The exploration of covalent organic frameworks (COFs) for high-efficiency photocatalytic CO2 reduction is urgently demanded. Herein, COF-based catalysts are constructed for the selective photoreduction of CO2 to CO via delicately designed isomeric monomers with substituent at the 4,5,9,10- positions (K) or 1,3,6,8-positions (A) of pyrene knots. The distinct substituted regions significantly affect the planarity of pyrene knots, resulting in COFs with different microstructures and photocatalytic activities. While employing a 5 W LED white-light as the light source, the single atomic Co contained A-Py-Bpy-COF-Co showcased a moderate CO evolution rate of 2174.4 µmol g-1 h-1. In sharp contrast, K-Py-Bpy-COF-Co reveals a considerable CO photo-reduction rate of 12 476.4 µmol g-1 h-1 (5.7 times higher than A-Py-Bpy-COF) with a selectivity up to 93.3%. Remarkably, the excellent photocatalytic activity of K-Py-Bpy-COF-Co can be maintained for at least 5 cycles without obvious decay. The distinct photocatalytic properties of the two isomeric COFs can be attributed to the larger steric-hindrance of K-Py-4CHO which enlarges the interlayer distances to inhibit exciton quenching and electron-richer nature of monatomic Co in K-Py-Bpy-COF-Co. This work provides a new protocol to explore COFs with boosted photocatalytic performance via isomeric design from refined modulation of reported COFs.

(General Student Poster Award Winner, 3rd Place) Solar CO2 Reduction to Form Green Syngas Employing a Black Cu3VS4 Photocathode Utilizing a Whole Range of Visible Light

A photoelectrochemical cell as artificial photosynthesis is an attractive system for solar CO2 reduction in H2O to produce a mixture gas of H2 and CO, so called “green syngas.” Development of photocathodes with the response to long wavelength visible light and high selectivity for CO formation is necessary in terms of efficient solar energy conversion. Recently, we reported that a powder-based Cu3VS4 black photocathode was active for solar H2 production utilizing a whole range of visible light.1 This photocathode was a Cu(Ⅰ)-containing metal sulfide, which was a suitable material for solar CO2 reduction.2 Therefore, solar CO2 reduction using a Cu3VS4 photocathode is expected to be achieved by constructing a photoelectrochemical cell. In the present study, we developed a new photoelectrochemical cell employing a black Cu3VS4 photocathode for solar CO2 reduction to produce green syngas.The black metal sulfide was prepared by a solid-state-reaction (SSR) and a flux method using a mixture of chloride salts (flux).1 The powder-based Cu3VS4 photocathode was fabricated by a particle transfer method contacted with deposited Au as a conductive layer.1,3 A sputtered Au cocatalyst was loaded on the photocathode. Photocathodic properties were measured using a three-electrode system under CO2 atmosphere. The photocathode was irradiated with visible light and simulated sunlight using a 300 W Xe-lamp attached with a long-pass filter and a solar simulator, respectively. The amounts of evolved H2, CO and O2 were determined using an online gas-chromatograph.Single particle layers with Cu3VS4 (SSR, flux) particles were observed on the photocathodes by SEM images. Large Cu3VS4 (SSR) particles with a size of 5-8 µm contacted with deposited Au layer roughly, while fine contacts with the Au layer were constructed due to small Cu3VS4 (flux) particles with a size of 200-800 nm. The results of SEM-EDS mappings and XPS measurements indicated that the surfaces of Cu3VS4 (SSR, flux) particles were mostly covered with a sputtered Au cocatalyst and a deposited Au layer. Photoelectrochemical CO2 reduction to form a green syngas using the Cu3VS4 photocathodes proceeded under visible light irradiation. During the reaction, green syngas including 24% of CO was successfully obtained using a Cu3VS4 (flux) photocathode. The comparatively high selectivity for CO evolution was due to the 2-type Au functioning as efficient active sites. It was notable that a stability of the photocurrent was drastically improved by employing fine Cu3VS4 (flux) particles instead of large Cu3VS4 (SSR) particles. XRF analysis and SEM images of the photocathode revealed that a large amount of the Cu3VS4 (SSR) particles were peeled off from the Au-deposited substrate after the reaction, while the Cu3VS4 (flux) particles were not. Therefore, the good stability of the photocurrent on the Cu3VS4 (flux) photocathode was due to the good contacts between the photocatalyst particles and the deposited Au layer. The onset of the IPCE agreed well with that of an absorption edge of Cu3VS4, reaching up to 820 nm. In other words, the black photocathode produced a green syngas utilizing a whole range of visible light. Finally, a photoelectrochemical cell consisting of the Cu3VS4 photocathode and a BiVO4 photoanode was constructed. Solar CO2 reduction proceeded applying the bias at 1.0 V between the photocathode and the photoanode. H2 and CO steadily evolved accompanied by O2 evolution from water, reaching unity of the ratio of reacted electrons to holes. These results indicated that solar CO2 reduction to form a green syngas using the Cu3VS4 photocathode was successfully achieved utilizing water as an electron donor.Thus, it was concluded that a Cu3VS4 photocathode with the high selectivity for CO evolution and the response to long wavelength visible light was successfully developed. Our findings will contribute to development of a photoelectrochemical cell for an efficient solar energy conversion and a sustainable carbon neutrality.[1] H. Fukai, K. Nagatsuka, Y. Yamaguchi, A. Iwase, A. Kudo, ECS J. Solid State Sci. Technol. 2022, 11, 063002.[2] S. Yoshino, T. Takayama, Y. Yamaguchi, A. Iwase, A. Kudo, Acc. Chem. Res. 2022, 55, 966.[3] T. Minegishi, N. Nishimura. J. Kubota, K. Domen, Chem. Sci. 2013, 4, 1120. Figure 1

Understanding High Voltage Electrolyte Reactivity on Cation-Disordered Rock Salt Cathodes

Li-ion battery demand is expected to increase dramatically to meet rapidly increasing energy storage demands. To address the expense and scarcity of cobalt and nickel used in current layered oxide cathodes, alternative cathode materials that rely on earth-abundant transition metals must be explored. Promising such materials are cation-disordered rocksalt (DRX) oxides, particularly those that are comprised of manganese and titanium, along with lithium excess to allow for high reversible capacities (>300 mAh/g). A substantial fraction of extractable lithium capacity in DRX materials occurs at high voltages, creating high energy density, but also leading to deleterious degradation processes. Recent studies have observed reactivity of the DRX surface when cycled to high voltages: >25% of transition metals migrating out of the cathode and continuous evolution of CO2 after 150 cycles [1]. 13C labeling has identified the carbonate electrolyte as the primary source of the CO2 after the first cycle [2]. This reactivity leads to a sharp increase in impedance and rapid capacity fade [1]. However, the exact cause of high voltage reactivity is still not fully understood for the electrolyte – DRX interface.In this study, we quantify the surface reactivity of select electrolyte – DRX systems using operando gas measurements and inductively coupled plasma – optimal emission spectrometry (ICP-OES). Through this method, we can identify what electrolyte and DRX properties have the largest influence on surface reactivity. To monitor surface reactivity of the electrolyte, differential electrochemical mass spectrometry (DEMS) was used to quantify evolution of CO2 and other gaseous products during cycling. To track the surface reactivity of the DRX, ICP-OES was used to quantify transition metal dissolution. We show that ethylene carbonate oxidation is particularly problematic above 4.4 V, and that processes involving the conductive carbon, as well as Mn and O redox are culpable. The results of this study provide insight into the primary causes of capacity fade in DRX-based batteries, informing future designs of the electrolyte, DRX, and other cathode materials.[1]: Matthew J. Crafton et al 2024 J. Electrochem. Soc. 171 020530[2]: Manuscript in Preparation: Tzu-Yang Huang et al 2024. Chem. Of Mat. (Manuscript ID: cm-2024-007563)