Photocatalytic CO2 Reduction Research Articles

Efficient methane production from photocatalytic CO2 reduction by InCu0.05Co0.05Ox: The synergistic effect of Co and Cu

Photocatalytic reduction of CO2 to methane (CH4) is a promising strategy to address CO2 emissions and energy scarcity. However, low efficiency limits its practical application. This study presents a bimetallic co-doping strategy using Cu and Co to enhance the photocatalytic performance of the In2O3 catalyst. The InCu0.05Co0.05Ox (InCuCo) catalyst demonstrated a CH4 yield of 22.3 µmol·g−1·h−1, outperforming In2O3 (8.8 µmol·g−1·h−1), InCu (14.5 µmol·g-1·h−1), and InCo (18.0 µmol·g-1·h−1). This remarkable improvement highlights the synergistic effects of Cu and Co in the In2O3 catalyst. Characterizations and density functional theory (DFT) calculations revealed that Co doping narrows the bandgap of the catalyst, enhancing light utilization, while Cu adjusts the energy band positions and improves CO2 adsorption. Consequently, the InCuCo catalyst significantly enhances the photocatalytic reduction of CO2–CH4, offering remarkable activity and stability. These results provide new insights into CO2 photoreduction to CH4, facilitating further practical applications.

MOF-derived phase-selective synthesis of ln2O3 with appropriate surface atomic arrangement for CO2 photoreduction

Crystal phase engineering emerges as a powerful strategy to enhance photocatalytic activity, yet controlled phase-selective synthesis and phase-dependent performance understanding remain challenging. In this study, we introduce a novel method for synthesizing phase-engineered In2O3 via the pyrolysis of metal–organic frameworks (MOFs). We demonstrate that the functional groups and pyrolysis temperatures of MOFs are critical for phase-selective synthesis. Specifically, pyrolysis of MIL-68(ln)–NH2 at optimal temperatures yields In2O3 with rhombohedral (rh-In2O3), cubic (c-In2O3), and rhombohedral/cubic heterophase (rh/c-In2O3) structures. Our photocatalytic CO2 reduction tests reveal that c-In2O3 outperforms rh-In2O3 and rh/c-In2O3, achieving a CO production rate of 29.19 μmol g-1h−1 with 94.47 % selectivity. Spectroscopic and theoretical analyses show that c-In2O3 has superior charge transfer efficiency and lower reaction energy barriers, particularly for the rate-determining *CO intermediate, which exhibits a lower Gibbs free energy on its surface. This work provides a significant advancement in optimizing photocatalytic CO2 reduction efficiency through precise phase engineering, underscoring the vital role of phase control in enhancing catalytic performance.

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.

Facet-Dependent Photocatalytic CO2 Reduction on TiO2 Crystals in the Presence of SO2: Role of Surface Hydroxyl.

Photocatalytic CO2 reduction to solar energy makes great sense to mitigate the greenhouse effect caused by CO2, and great efforts have been made to promote CO2 conversion efficiency. However, the effect of impurities in the photoreduction of CO2 has received relatively little attention. Here, the different CO2 photoreduction behaviors of TiO2 exposed (101) facet (TiO2-101) and (001) facet (TiO2-001) with an SO2 impurity were investigated. On TiO2-101, SO2 accelerates the deactivation of the catalyst for CO2 photoreduction activity, since SO2 mainly binds to the OHb site of TiO2-101. This site is highly susceptible to the transfer of photogenerated holes, resulting in the rapid generation of SO42-, which occupies the active site and poisons the catalyst. For TiO2-001, SO2 has relatively little negative effect on stability, as SO2 mainly binds to the weak binding site (OHt) of TiO2-001, preventing it from being oxidized to SO42-, which alleviates catalyst deactivation and ensures the continuity of CO2 reduction. This paper provides further insights into the role of SO2 in CO2 photoreduction over distinct TiO2 facets and reveals the importance of facet engineering in the photocatalytic reduction of CO2 from industrial flue gas.

Novel Single Perovskite Material for Visible-Light Photocatalytic CO2 Reduction via Joint Experimental and DFT Study.

Developing advanced and economically viable technologies for the capture and utilization of carbon dioxide (CO2) is crucial for sustainable energy production from fossil fuels. Converting CO2 into valuable chemicals and fuels is a promising approach to mitigate atmospheric CO2 levels. Among various methods, photocatalytic reduction stands out for its potential to reduce emissions and produce useful products. Here, novel perovskite ZnMoFeO3 (ZMFO) nanosheets are presented as promising semiconductor photocatalysts for CO2 reduction. Experimental results show that ZMFO has a narrow bandgap, exceptional visible light response, large specific surface area, high crystallinity, and various surface-active sites, leading to an impressive photocatalytic CO2 reduction activity of 24.87 µmolg-1h-1 and strong stability. Theoretical calculations reveal that CO2 conversion into CO and CH4 on the ZMFO surface follows formaldehyde and carbine pathways. This study provides significant insights into designing innovative perovskite oxide-based photocatalysts for economical and efficient CO2 reduction systems.

Single-Atom-Layer Metallization of Plasmonic Semiconductor Surface for Selectively Enhancing IR-Driven Photocatalytic Reduction of CO2 into CH4.

Efficient harvesting and utilization of abundant infrared (IR) photons from sunlight is crucial for the industrial application of photocatalytic CO2 reduction. Plasmonic semiconductors have significant potential in absorbing low-energy IR photons to generate energetic hot electrons. However, modulating these hot electrons to selectively enhance the activity of CO2 reduction into CH4 remains a challenge. Herein, the study proposes a single-atom-layer (SAL) metallization strategy to enhance the generation of IR-driven hot electrons and facilitate their transfer from plasmonic semiconductors to CO2 for producing CH4. This strategy is demonstrated using a paradigmatic W18O49@W-Sn nanowire array (NWA), where Sn2+ ions are grafted onto exposed O atoms on the surface of plasmonic W18O49 to form a surface W-Sn SAL. The incorporation of Sn single atoms enhances plasmonic absorption in IR light for W18O49 NWA. The W-Sn SAL not only promotes CO2 adsorption and reduces its reaction activation energy barrier but also shifts the endoergic CO-protonation process toward an exoergic reaction pathway. Thus, the W18O49@W-Sn NWA exhibits >98% selectivity for IR-driven CO2 reduction to CH4 with an activity over 9.0 times higher than that of bare W18O49 NWA. This SAL metallization strategy can also be applied to other plasmonic semiconductors for selectively enhancing CO2-to-CH4 reduction reactions.

Efficient photoreduction of CO2 to CO by Co-ZIL-L derived NiCo-OH with ultrathin nanosheet assembled 2D leaf superstructure.

The photocatalytic reduction of CO2 into valuable chemicals and fuels is considered a promising solution to address the energy crisis and environmental challenges. In this work, we introduce a Co-ZIL-L mediated in situ etching and integration process to prepare NiCo-OH with an ultrathin nanosheet-assembled 2D leaf-like superstructure (NiCo-OH UNLS). The resulting catalyst demonstrates excellent photocatalytic performance for CO2 reduction, achieving a CO evolution rate as high as 309.5 mmol g-1 h-1 with a selectivity of 91.0%. Systematic studies reveal that the ultrathin nanosheet structure and 2D leaf-like architecture not only enhance the transfer efficiency of photoexcited electrons but also improve the accessibility of active reaction sites. Additionally, the Ni-Co dual sites in NiCo-OH UNLS accelerate CO2 conversion kinetics by stabilizing the *COOH intermediate, significantly contributing to its high activity. This work offers valuable insights for designing advanced photocatalysts for CO2 conversion.

Enhancing Internal Electric Field of Metal-Free Donor-Acceptor Conjugated Photocatalysts for Efficient Photocatalytic Degradation of Tetracycline and CO2 Reduction.

Constructing alternating donor-acceptor (D-A) units within g-C3N4 represents an effective strategy for enhancing photocatalytic performance through improved charge carrier separation while concurrently addressing energy shortages and facilitating wastewater remediation. Here, a series of D-A-type conjugated photocatalysts (CNBTC-X) are prepared using g-C3N4 as an acceptor unit and different masses of 5-bromo-2-thiophenecarboxaldehyde (BTC) as a donor unit by a one-step thermal polymerization. CNBTC-50 presents higher photocatalytic properties for CO2 reduction coupled with tetracycline (TC) removal than those of g-C3N4, CNBTC-10, CNBTC-30, and CNBTC-70. The introduction of the unique electron-donor-acceptor structure effectively drives the separation and transfer of photoinduced carriers while reducing the internal carrier transfer hindrance. Photocatalytic experiments reveal that the CNBTC-50 photocatalyst achieves up to 94.6% TC removal under visible light irradiation conditions. Compared with that of the pristine g-C3N4, the photocatalytic degradation reaction rate constant of CNBTC-50 is significantly increased by about 3.87 times. The study examines the influence of various reaction parameters on degradation activity, including catalyst concentration, pH, and TC concentration. Additionally, LC-MS is utilized to perform a comprehensive analysis of the intermediates and pathways involved in TC degradation. Furthermore, CNBTC-50 demonstrates remarkable photocatalytic CO2 reduction activity, achieving rates of 20.83 μmol g-1 h-1 (CO) and 9.36 μmol g-1 h-1 (CH4), which are 10.68 and 5.98 times more efficient than those of g-C3N4, respectively. This work aims to offer valuable guidance for the rational design of nonmetal D-A-structured catalysts and effectively integrates reaction systems to couple CO2 reduction with antibiotic removal.

Hydrogen- assisted synthesis of defective triazine/heptazine homostructured nanosheets for efficient CO2photoreduction.

Homostructure construction has been demonstrated to be an effective way for boosting the photocatalytic activity of polymeric carbon nitride. However, the contribution of the intrinsic activity of molecular fragments in the catalytic performance of homostructured carbon nitride is yet to be explored. In this paper, a facile hydrogen-assisted strategy was used to synthesize triazine/heptazine intermolecular homojunctions (g-C3N4(MU-H)) with an ultrathin and defective structure, via the co-pyrolysis of melamine and urea precursors. Experimental characterizations and theoretical calculations revealed the copolymerization of triazine- and heptazine-based carbon nitride generated a homostructured interface with a large build-in electric field for efficient separation of photogenerated carriers. Due to the synergestic effect between the homostructured interface and nitrogen vacancies, as-synethesized g-C3N4(MU-H) exhibited an outstanding activity for photocatalytic CO2 reduction, with a CO yield rate of 14.45 μmol h-1, which was 23.5 and 3.64 times higher than those of bulk g-C3N4 and g-C3N4(M-H) synthesized from a single precursor, respectively. This study provides a new avenue for optimizing the charge separation efficiency of CO2 photoreduction catalysts by constructing intramolecular homojunction.

Enabling Interfacial Lattice Matching by Selective Epitaxial Growth of CuS Crystals on Bi2WO6 Nanosheets for Efficient CO2 Photoreduction into Solar Fuels.

Photocatalytic CO2 reduction serves as an important technology for value-added solar fuel production, however, it is generally limited by interfacial charge transport. To address this limitation, a two-dimensional/two-dimensional (2D/2D) p-n heterojunction CuS-Bi2WO6 (CS-BWO) with highly connected and matched interfacial lattices was designed in this work via a two-step hydrothermal tandem synthesis strategy. The integration of CuS with BWO created a robust interface electric field and provided fast charge transfer channels due to the work function difference, as well as highly connected and matched interfacial lattices. The p-n heterojunction combination promoted the electron transfer from the Cu to Bi sites, leading to the coordination of Bi sites with high electronic density and low oxidation state. The Bi sites in the BWO nanosheets facilitated the adsorption and activation of CO2, and the generation of high-coverage key intermediate b-CO3 2-, while CuS (CS) acted as a broad light-harvesting material to provide abundant photoinduced electrons that were injected into the conduction band of BWO for CO2 photoreduction reaction. Remarkably, the p-n heterojunction CS-BWO exhibited average CO and CH4 yields of 33.9 and 16.4 μmol g-1 h-1, respectively, which were significantly higher than those of CS, BWO, and physical mixture CS-BWO samples. This work provided an innovative design strategy for developing high-activity heterojunction photocatalyst for converting CO2 into value-added solar fuels.

Surface Sulfurization of Cubic Cu2O to Form Cu2S Nanostructure-Decorated Catalysts for Light-Enhanced Electrocatalytic H2 Evolution and Photocatalytic CO2 Reduction.

Developing highly efficient bifunctional catalysts for electrocatalysis and photocatalysis suffers from sluggish charge transfer and poor photo-to-electric conversion rate. Herein, micro-sized Cu2O cubes were initially prepared for subsequent transformation into Cu2O@Cu2S core-shell structures by a slight surface sulfurization. The formation of nanostructured Cu2S thin layer at Cu2O surface can endow an immediate charge separation and migration under light irradiation, leading to high surface photovoltages (SPV, 18-30 mV). As a result, the as-prepared Cu2O@Cu2S catalysts exhibited reduced overpotentials (η, only 86 mV is required for the optimized sample to achieve a current density of 10 mA cm-2) for H2 evolution with good cycling stability in electrocatalytic water splitting. Meanwhile, a high methane (CH4) production rate of 30.3 μmol h-1 g-1 can be delivered from the optimized Cu2O@Cu2S sample when used for photocatalytic CO2 reduction. This work has provided a strategy to prepare bifunctional catalysts with improved photoelectric properties for photo/electrocatalytic applications.

Prolonging Charge Carrier Lifetime via Intraband Defect Levels in S-Scheme Heterojunctions for Artificial Photosynthesis.

S-scheme heterostructure photocatalysts, distinguished by unique charge-transfer pathways and exceptional catalytic redox capabilities, have found widespread applications in addressing challenging chemical processes, including the photocatalytic reduction of CO2 with a high reaction barrier. Nevertheless, the influence of intraband defect levels within S-scheme heterojunctions on charge separation, carrier lifetime, and surface catalytic reactions has, for the most part, been overlooked. Herein, we develop a tunable defect-level-assisted strategy to construct an electron reservoir, effectively prolonging the lifetime of charge carriers through the rapid capture and gradual release of photoelectrons within WO3-x/In2S3 S-scheme heterojunctions, as authenticated by femtosecond transient absorption spectroscopy and theoretical simulations. The surface photoredox mechanism, unraveled by Gibbs free energy calculations, demonstrates that oxygen-vacancy-induced defect states in WO3-x/In2S3 heterojunctions unlock the rate-determining H2O oxidation into free oxygen molecules by forming metastable oxygen intermediates, contributing to the facilitation of H2O photooxidation. This distinct role, combined with the extended carrier lifetime, results in boosted CO2 photoreduction with nearly 100 % CO selectivity in the absence of any photosensitizer or scavenger. Our work sheds light on the role of controllable defect levels in governing charge transfer dynamics within S-scheme heterojunctions, thereby inspiring the development of more advanced photocatalysts for artificial photosynthesis.

Enhanced Charge Transfer in Poly(Heptazine Imide) Synergistically Induced by Donor-Acceptor Motifs and Ohmic Junctions for Efficient Photocatalytic CO2 Reduction.

Poly(heptazine imide) (PHI) has received widely interest in the photocatalytic CO2 reduction due to its good crystallinity and complete in-plane structure. However, its poor photo-induced carrier separation and migration efficiency and insufficient active sites results in undesirable photocatalytic CO2 reduction performance. Herein, we designed and constructed a novel ohmic junction photocatalyst by integrating melamine edge-modified PHI (mel-PHI) with extended π-conjugated system with TiN (TiN/mel-PHI) for enhancing the photocatalytic CO2 reduction activity. Strikingly, the photocayalytic CO2 reduction yield of the optimal TiN/mel-PHI is 62.64 µmol·g-1·h-1, which is 5.6 and 2.8 times higher than PHI (11.26 µmol·g-1·h-1) and mel-PHI (22.32 µmol·g-1·h-1), respectively. The superior photocatalytic CO2 reduction activity is attributed not only to the formation of D-A structure by the introduction of melamine, which extends the π-conjugation system, alters the electronic structure of PHI, and accelerates the charge separation and migration, but also to the induced internal electric field by ohmic junction further enhances the charge separation and migration efficiency. Meanwhile, the synergistic effect of mel-PHI and TiN enriched the electron number of TiN, reducing the CO2 reduction potential. This work highlights the synergistic enhancement of charge transfer between D-A motifs and ohmic junctions, confirming their potential in optimizing photocatalysts.

CuO/CeO2 Nanocomposites with p‐n Heterojunction for Photocatalytic CO2 Reduction to CH4

CH4 is a significant fuel with considerable industrial value. And photocatalytic CO2 reduction presents an effective strategy for producing CH4, offering a green, environmentally friendly, and sustainable solution. However, challenges such as inefficient light absorption and inadequate separation and transport of photogenerated electron‐hole pairs are crucial barriers to its progress. Herein, an efficient CuO/CeO2 photocatalyst with p‐n heterojunction was prepared for the photocatalytic reduction of CO2 to CH4. CuO/CeO2 exhibited improved light absorption efficiency, along with enhanced separation and transport of photogenerated charges, leading to superior photocatalytic performance compared with individual CuO and CeO2. Only CO was detected on CuO or CeO2. In contrast, CuO/CeO2 produced CH4 and C2H4 at yields of 80.2 μmol·g‐1 and 2.1 μmol·g‐1 within 4 h, respectively. And the selectivity for CH4 reached 97.4%.

The Reduced Barrier for the Photogenerated Charge Migration on Covalent Triazine‐Based Frameworks for Boosting Photocatalytic CO2 Reduction Into Syngas

AbstractPhotocatalytic CO2 reduction together with hydrogen generation is a promising approach to generate syngas, the photogenerated electron migration from photosensitizers to the catalytic active sites is the rate‐determining step. Herein, an integrative strategy is presented by covalently grafting metal complexes into donor–acceptor covalent triazine‐based frameworks. The catalytic active sites are integrated with the photosensitizer units by covalent linkages to form an extended π‐conjugated framework, which significantly reduces the energy barrier for the migration of the photogenerated charge carriers, resulting in high activity and durability in photocatalytic CO2 reduction into syngas under visible light irradiation. The CO and H2 evolution amounts in 1.5 h are 1086 and 1042 µmol g−1, respectively, which greatly surpass those in the host‐guest counterparts. Furthermore, selective adsorption for CO2 over N2 renders this photocatalytic system to be effective for syngas production from the simulated flue gas. This study provides new approaches to construct the integrative photocatalytic systems for solar‐to‐chemical energy conversion.

Potassium and Boron Co-Doping of g-C3N4 Tuned CO2 Reduction Mechanism for Enhanced Photocatalytic Performance: A First-Principles Investigation.

Graphitic phase carbon nitride (g-C3N4, abbreviated as CN) can be used as a photocatalyst to reduce the concentration of atmospheric carbon dioxide. However, there is still potential for improvement in the small band gap and carrier migration properties of intrinsic materials. K-B co-doped CN (KBCN) was investigated as a promising photocatalyst for carbon dioxide reduction via the Density Functional Theory (DFT) method. The electronic and optical properties of CN and KBCN indicate that doping K and B can improve the catalytic performance of CN by promoting charge migration and separation. In terms of the Gibbs free energy change, the CO2 reduction reaction catalysed by KBCN results in CH3OH, and its optimal pathway is CO2 → *CO2 → *COOH → CO → *OCH → HCHO → *OCH3 → CH3OH. Compared with CN, the doping elements K and B shift the rate-determining step from CO2 → *CO2 to *CO2 → *COOH. The K and B elements co-doping tuned the charge distribution between the catalyst and the adsorbate and reduced the Gibbs free energy of the rate-determining step from 1.571 to 0.861 eV, suggesting that the CO2 reduction activity of KBCN is superior to that of CN. Our work provides useful insights for the design of metallic-nonmetallic co-doped CN for photocatalytic CO2 reduction (CO2PR) reactions.

Water-Induced Switching in Selectivity and Steric Control of Activity in Photochemical CO2 Reduction Catalyzed by RhCp*(bpy) Derivatives.

Photocatalytic reduction of CO2 to formic acid (HCOOH) was investigated in either organic or aqueous/organic media by employing three water-soluble [RhIIICp*(LH2)Cl]+ (LH2 = n,n'-dihydroxy-2,2'-bipyridine; n = 4, 5, or 6) in the presence of [Ru(bpy)3]2+, 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) and triethanolamine (TEOA). Through studying the electron-donating effects of two hydroxyl groups introduced into the bipyridyl ligand, we found that the substituent positions greatly affect both the catalytic efficiency and selectivity in CO2 reduction. More importantly, the HCOOH selectivity shows a dramatic increase from 14 to 83% upon switching the solvent media from pure organic to an aqueous/organic mixture, where the H2 selectivity shows a reverse phenomenon. The enhanced HCOOH selectivity and the drastic decrease in the H2 yield are well rationalized by the fact that the catalytic CO2 hydrogenation is not only driven photochemically via the attack of RhIII(H)Cp*(LH2-·) on CO2 but also partly bypassed by a dark H2 addition reaction yielding [RhIII(H)Cp*(L)]- from [RhIIICp*(L)Cl]+, which was also separately investigated under dark conditions. A combination of experimental and theoretical approaches was made to clarify the pKa values of catalyst intermediates together with the abundant species responsible for the major catalytic processes. Our DFT studies unveil that the exceptionally large structural strain given by the steric contacts between the 6,6'-dihydroxyl groups and the Cp* moiety plays a significant role in bringing about an outstanding catalytic performance of the 6,6'-substituted derivative. The intrinsic reaction coordinate calculations were carried out to clarify the mechanism of hydride transfer steps leading to generating formate together with the heterolytic H2 cleavage steps leading to afford the key hydridorhodium intermediates. This study represents the first report on the water-induced high selectivity in CO2-to-HCOOH conversion, shedding new light on the strategy to control the efficiency and selectivity in the catalysis of CO2 reduction.

Simultaneous Photocatalytic CO2 Reduction and H2O Oxidation Under Non-Sacrificial Ambient Conditions.

The utilization of CO2, H2O, and solar energy is regarded as a sustainable route for converting CO2 into chemical feedstocks, paving the way for carbon neutrality and reclamation. However, the simultaneous photocatalytic CO2 reduction and H2O oxidation under non-sacrificial ambient conditions is still a significant challenge. Researchers have carried out extensive exploration and achieved dramatic developments in this area. In this review, we first primarily elucidate the principles of two half-reactions in the photocatalytic conversion of CO2 with H2O, i. e., CO2 reduction by the photo-generated electrons and protons, and H2O oxidation by the photo-generated holes without sacrificial agents. Subsequently, the strategies to promote two half-reactions are summarized, including the vacancy/facet/morphology design, adjacent redox site construction, and Z-scheme heterojunction development. Finally, we present the advanced in situ characterizations and future perspectives in this field. This review aims to provide fresh insights into effectively simultaneous photocatalytic CO2 reduction and H2O oxidation under non-sacrificial ambient conditions.

Reductive Transformation of CO2 to Organic Compounds.

Carbon dioxide is a major greenhouse gas and a safe, abundant, easily accessible, and renewable C1 resource that can be chemically converted into high value-added chemicals, fuels and materials. The preparation of urea, organic carbonates, salicylic acid, etc. from CO2 through non-reduction conversion has been used in industrial production, while CO2 reduction transformation has become a research hotspot in recent years due to its involvement in energy storage and product diversification. Designing suitable catalysts to achieve efficient and selective conversion of CO2 is crucial due to its thermodynamic stability and kinetic inertness. From this perspective, the redistribution of charges within CO2 molecules through the interaction of Lewis acid/base or metal complexes with CO2, or the forced transfer of electrons to CO2 through photo- or electrocatalysis, is a commonly used effective way to activate CO2. Based on understanding of the activation/reaction mechanism on a molecular level, we have developed metal complexes, metal salts, inorganic/organic salts, ionic liquids, as well as nitrogen rich and porous materials as efficient catalysts for CO2 reductive conversions. The goal of this personal account is to summarize the catalytic processes of CO2 reductive conversion that have been developed in the past 7 years: 1) For the reductive functionalization of CO2, the major challenge lies in accurately adjusting reaction parameters (such as pressure) to achieve high catalytic efficiency and the product selectivity; 2) For photocatalytic or electrocatalytic reduction of CO2, how to suppress competitive hydrogen evolution reactions and improve catalyst stability are key points that requires continuous attention.

Computational screening of 2D ternary penta-materials with auxetic properties and efficient photocatalytic CO2 reduction

Due to unique structural and electronic properties, pentagon-based two-dimensional (2D) materials have captured significant interest in recent years. However, previous studies on these materials have primarily focused on unary and binary systems, with less exploration of ternary pentagonal structures. Herein, we conducted first-principles calculations to evaluate the stability of 122 ternary pentagonal monolayers composed of metals, nitrogen, and chalcogen. We identify six highly stable candidates, including AuNS, CuNTe, GaNS, InNS, SbNS, and SbNSe that meet the criteria for thermodynamic, mechanical, and dynamic stability. Mechanical property analysis reveals that five of these monolayers demonstrate auxetic behavior. Electronic structure calculations show that all candidates are semiconductors with band gaps ranging from 0.12 to 3.42 eV. Specifically, the SbNS and SbNSe monolayers are indirect semiconductors with band gaps of 2.25 and 2.27 eV, respectively. These materials exhibit strong visible light absorption, and potentially serve as exceptional photocatalysts for the reduction of CO2 to CH4 due to the optimal band alignment. The free energy change in the rate-limiting step is even lower than those found in g-C3N4 and MoS2-based systems. Our findings highlight new pentagon-based 2D materials with remarkable electronic, mechanical, and optical properties, making them promising candidates for applications in mechanics and energy conversion.