Photothermal catalysis for CO2 conversion

Improved CO2 conversion to methanol promoted by ionic liquid additives using a Cu/ZnO/Al2O3 heterogeneous catalyst

An efficient amine-based CO2 hydrogenation to methanol system using a Cu/ZnO/Al2O3 heterogeous catalyst was promoted by ionic liquid additives. Relative to a system without an ionic liquid, methanol yields greatly improved when an imidazolium-based ionic liquid [BMIm][OAc] was added. Among the amines tested, triethanolamine yielded the highest conversions.

CuCo2S4/g-C3N4-x S-Scheme Heterojunction for Photothermal-Assisted Photocatalytic CO2 Reduction

Photocatalytic conversion of CO2 into chemical fuels has emerged as a research hotspot, aiming to mitigate the rapid depletion of fossil fuels and alleviate global warming. However, the inherent low carrier separation efficiency and limited solar light utilization of photocatalysts lead to unsatisfactory CO2 conversion efficiency. In this study, an appealing CuCo2S4/g-C3N4-x S-scheme heterostructure is successfully fabricated by a simple polyol reflux method. Notably, nitrogen vacancies enhance the Fermi level difference between CuCo2S4 and g-C3N4-x, resulting in a stronger interfacial built-in electric field. The full-spectrum strong optical absorption capability endows the synthesized catalysts with superior light-harvesting property. The photothermal effect-induced temperature increase accelerates the cyclic process of CO2 adsorption and CO desorption on the catalyst surface. Most importantly, the S-scheme charge transfer pathway ensures the efficient separation of photogenerated carriers. Thanks to these synergistic benefits, CuCo2S4/g-C3N4-x exhibits exceptional photothermal-assisted photocatalytic CO2 reduction performance. Under simulated sunlight, the average CO production rate of CuCo2S4/g-C3N4-x reaches 24.64 μmol g-1 h-1, which is 12.1 and 27.1 times higher than that of g-C3N4 and CuCo2S4, respectively. This study offers a novel strategy for designing photocatalysts with outstanding CO2 conversion performance.

Self-sacrificial synthesis of Cu3(HHTP)2 on Cu substrate for recyclable NH3 gas adsorption with energy-efficient photothermal regeneration

The efficient adsorption and removal of toxic gases, particularly ammonia (NH3), remains a critical challenge in environmental management and industrial safety. Metal-organic frameworks (MOFs) have emerged as promising gas adsorbents due to their tunable structures and high surface area. However, the strong interaction between NH3 and MOFs poses challenges for the regeneration and reusability of MOF adsorbents, often requiring energy-intensive desorption methods. This study proposes a sustainable approach for regenerating adsorption sites for recyclable gas adsorbents. We present a facile method for the direct synthesis of Cu3(HHTP)2 on a Cu mesh substrate (Cu3(HHTP)2@Cu), utilizing the Cu metal itself as a precursor to eliminate the need for external metal sources. The resulting Cu3(HHTP)2@Cu serves as a recyclable NH3 adsorbent, leveraging the π-conjugated hexahydroxytriphenylene (HHTP) ligand for photothermal conversion under sunlight irradiation, where photo-generated heat facilitates NH3 desorption. The study further explores the effect of an external voltage on the NH3 adsorption performance and crystalline structure of Cu3(HHTP)2@Cu. Our findings demonstrate that Cu3(HHTP)2@Cu achieves efficient NH3 desorption through a minimally invasive and energy-efficient mechanism, addressing the limitations of conventional adsorbents.

Differential evolution-optimized gold nanorods for enhanced photothermal conversion

Noble metallic nanoparticles (NPs) have shown great potential in the field of sustainable energy. Gold nanorods (AuNRs), known for their size-dependent optical and electrical characteristics, are strong candidates for various applications, particularly in solar energy conversion. Additionally, AuNRs are well-established nanomaterials in precision medicine. In this paper, we optimize the shape and size of AuNRs to maximize light-to-heat conversion based on a validated theoretical model. Utilizing the Differential Evolution (DE) algorithm, a robust metaheuristic optimization approach, we calculated the optimal size and shape of AuNRs for selected wavelengths. The aspect ratio (AR), defined as the ratio of the diameter to the length of the AuNRs, was a key parameter in the optimization process. The optimization results reveal that for shorter wavelengths, near-spherical AuNRs (AR of 0.71 and 0.75) demonstrate the highest efficiency, while for longer wavelengths, more elongated AuNRs (AR of 0.24 and 0.17) outperform others. This study also includes Computational Fluid Dynamics (CFD) calculations to evaluate the impact of optimized AuNRs on heat generation in a real-world scenario. A case study is presented in which lasers of different wavelengths irradiate a borosilicate glass embedded with a slab of AuNRs at its center. The results, reported as temperature distributions and temperature evolution during irradiation, indicate that the optimized AuNRs significantly enhance heat generation across various laser wavelengths. Specifically, temperature increases were observed as follows: from 2.28 to [Formula: see text] at 465 nm, from 1.91 to [Formula: see text] at 532 nm, from 1.7 to [Formula: see text] at 640 nm, from 40 to [Formula: see text] at 808 nm, and from 0.94 to [Formula: see text] at 980 nm, respectively. These findings underscore the effectiveness of the optimization process in enhancing photothermal conversion.

Principle Design of C-C Coupling Pathway Towards Highly Selective C2 Products Using Photocatalytic CO2 Reduction:A Review

Photocatalytic conversion of environmental CO2 into valuable fuels is expected to alleviate fossil fuel and pollution problems. However, intricate product-reaction pathways complicate the regulation of product selectivity. Most studies in this field have focused on increasing productivity rather than on controlling product formation. To date, the major products of photocatalytic CO2 reduction reactions (CO2RRs) are C1 compounds, as opposed to the higher-value C2 compounds, because of the low C2 selectivity of this process. The design of C-C coupled pathways is paramount to facilitate selective access to C2 products in the photocatalytic CO2RR. In this review, we discuss the mechanisms and pathways of CO2RR product generation based on recent research results and summarise the work on CO2RR to C2 products. This review aims to modulate the product-generation pathway to improve the yield and selectivity of C2 products by facilitating C-C coupling reactions. Finally, some of the current challenges in the field of the CO2RR to C2 are outlined, including possible mechanistic interpretations, cost of catalyst use, reactor design, and potential solutions.

Comprehensive Insight into Indium Oxide‐Based Catalysts for CO2 Hydrogenation: Thermal, Photo, and Photothermal Catalysis

The conversion of carbon dioxide (CO2) into value‐added chemicals presents an innovative pathway for advancing the low‐carbon clean energy revolution, contributing significantly to CO2 emission reduction and resource utilization. Recently, In2O3‐based catalysts have emerged as a promising frontier in CO2 hydrogenation research. This review provides a comprehensive introduction of the latest advancements in the application of In2O3‐based catalysts across thermal, photocatalytic, and photothermal catalysis platforms. The review examines critical aspects such as structural properties, active sites, reaction mechanisms, performance enhancement, product impact, and the development of multi‐functional catalytic systems. Thermal Catalysis for CO2 hydrogenation involves the application of elevated temperatures to initiate and drive the hydrogenation reactions. Photocatalysis, on the other hand, harnesses light energy to facilitate these reactions. Among these approaches, photothermal catalysis has emerged as a particularly promising method for CO2 hydrogenation, offering several advantages over both thermal catalysis and photocatalysis. These advantages include more efficient energy utilization, a broader range of reaction conditions, enhanced synergistic effects, selective activation, and improved environmental sustainability. This review not only summarizes the current state of research in this field but also may provide critical insights and guidance for future studies aimed at advancing artificial carbon cycling processes.

MgCr2O4/MgIn2S4 Spinel/Spinel S-Scheme Heterojunction: A Robust Catalyst for Photothermal-Assisted Photocatalytic CO2 Reduction

Photocatalytic CO2 reduction technology has engaged significant attention due to its high efficiency, high selectivity, and environmental friendliness. However, its application is severely restrained by issues such as low separation efficiency of photogenerated carriers and a limited light absorption range. This work proposes an innovative MgCr2O4/MgIn2S4 magnesium-based spinel/spinel heterostructure photocatalyst to improve the photocatalytic CO2 reduction efficiency through the synergistic contributions of S-scheme heterojunction and photothermal effect. On the one hand, the unique S-scheme charge transfer mechanism enables the effective separation of photogenerated carriers. On the other hand, the photothermal effect allows an accelerated charge migration by increasing the reaction center temperature. Moreover, the abundant oxygen vacancies serve as electron traps and CO2 adsorption sites, unifying reaction and adsorption sites and substantially improving catalytic efficiency. Under UV-vis and UV-vis-NIR illumination, the average CO yields of the MgCr2O4/MgIn2S4 composite are 8.03 and 15.62 μmol g-1 h-1, respectively, greatly higher than those of pure MgCr2O4 and MgIn2S4 samples. Furthermore, the fabricated photocatalyst demonstrates excellent performance and structure stability. Therefore, this work may offer a new strategy for designing efficient and stable photocatalysts.

Applications of Ni-Based Catalysts in Photothermal CO2 Hydrogenation Reaction

Heterogeneous CO2 hydrogenation catalytic reactions, as the strategies for CO2 emission reduction and green carbon resource recycling, play important roles in alleviating global warming and energy shortages. Among these strategies, photothermal CO2 hydrogenation technology has become one of the hot catalytic technologies by virtue of the synergistic advantages of thermal catalysis and photocatalysis. And it has attracted more and more researchers' attentions. Various kinds of effective photothermal catalysts have been gradually discovered, and nickel-based catalysts have been widely studied for their advantages of low cost, high catalytic activity, abundant reserves and thermal stability. In this review, the applications of nickel-based catalysts in photothermal CO2 hydrogenation are summarized. Finally, through a good understanding of the above applications, future modification strategies and design directions of nickel-based catalysts for improving their photothermal CO2 hydrogenation activities are proposed.

Recent Progress of Studies on Photoconversion and Photothermal Conversion of CO2 with Single-Atom Catalysts

Catalytic conversion of carbon dioxide (CO2) into useful chemical raw materials or fuels can help achieve the "dual carbon" goals of carbon peaking and carbon neutrality. As a sustainable green energy source, solar energy provides energy for human production and life. In recent years, the reported single-atom catalysts (SACs) have higher atom utilization and better catalytic efficiency than traditional heterogeneous catalysts. In the field of photocatalysis and photothermal synergistic catalysis of CO2 conversion, single-atom catalysts can reduce the reaction temperature and pressure, improve the catalytic activity, and improve the selectivity of the reaction. In this mini-review, the basic mechanism and classification of CO2 reduction are introduced, and then the roles and differences of single-atom catalysts in photocatalysis and photothermal catalysis are introduced. In addition, according to the reduction product types, the recent research progress of single-atom catalysts in photoconversion and photothermal CO2 conversion was reviewed. Finally, the challenges of monoatomic photocatalytic and photothermal CO2 reduction technologies have prospected. This mini-review hopes to provide an in-depth understanding of the roles of single atoms in photocatalysis and photothermal catalysis and to shed light on the actual production and application of renewable energy. High-performance single-atom catalysts are expected to achieve industrial applications of CO2 conversion, which will contribute to the early realization of the two-carbon goal.

Integration of Co Single Atoms and Ni Clusters on Defect-Rich ZrO2 for Strong Photothermal Coupling Boosts Photocatalytic CO2 Reduction

We report a solvothermal method for the synthesis of an oxygen vacancy-enriched ZrO2 photocatalyst with Co single atoms and Ni clusters immobilized on the surface. This catalyst presents superior performance for the reduction of CO2 in H2O vapor, with a CO yield reaching 663.84 μmol g-1 h-1 and a selectivity of 99.52%. The total solar-to-chemical energy conversion efficiency is up to 0.372‰, which is among the highest reported values. The success, on one hand, depends on the Co single atoms and Ni clusters for both extended spectrum absorption and serving as dual-active centers for CO2 reduction and H2O dissociation, respectively; on the other hand, this is attributed to the enhanced photoelectric and thermal effect induced by concentrated solar irradiation. We demonstrate that an intermediate impurity state is formed by the hybridization of the d-orbital of single-atom Co with the molecular orbital of H2O, enabling visible-light-driven excitation over the catalyst. In addition, Ni clusters play a crucial role in altering the adsorption configuration of CO2, with the localized surface plasmon resonance effect enhancing the activation and dissociation of CO2 induced by visible-near-infrared light. This study provides valuable insights into the synergistic effect of the dual cocatalyst toward both efficient photothermal coupling and surface redox reactions for solar CO2 reduction.

Noncrystalline Zeolitic Imidazolate Frameworks Tethered with Ionic Liquids as Catalysts for CO2 Conversion into Cyclic Carbonates

Noncrystalline zeolitic imidazolate frameworks (ZIFs) tethered with ionic liquids (ILs) were successfully employed as catalysts for mild CO2 conversion into cyclic carbonates for the first time. Notably, noncrystalline ZIFs exhibit outstanding catalytic performance in terms of activity, stability, and substrate suitability. Z3 was obtained through the simultaneous incorporation of a boronic acid group and ILs into its ZIF framework and exhibited a superior catalytic activity. A reaction mechanism for the propylene oxide-CO2 cycloaddition has been proposed, which integrates experimental findings with density functional theory calculations. The results indicate that zinc, ILs, and boronic acid play crucial roles in achieving high activity. Zinc and ILs are identified as key contributors to epoxide activation and ring opening, while boronic acid plays a crucial role in stabilizing the turnover frequency-determining transition states. The simplicity of this ZIF synthesis approach, combined with the high activity, stability, and versatility of the products, facilitates practical and efficient conversion of CO2 and epoxides into cyclic carbonates.

Solar-Driven Continuous CO2 Reduction to CO and CH4 using Heterogeneous Photothermal Catalysts: Recent Progress and Remaining Challenges

The urgent need to reduce the carbon dioxide level in the atmosphere and keep the effects of climate change manageable has brought the concept of carbon capture and utilization to the forefront of scientific research. Amongst the promising pathways for this conversion, sunlight-powered photothermal processes, synergistically using both thermal and non-thermal effects of light, have gained significant attention. Research in this field focuses both on the development of catalysts and continuous-flow photoreactors, which offer significant advantages over batch reactors, particularly for scale-up. Here, we focus on sunlight-driven photothermal conversion of CO2 to chemical feedstock CO and CH4 as synthetic fuel. This review provides an overview of the recent progress in the development of photothermal catalysts and continuous-flow photoreactors and outlines the remaining challenges in these areas. Furthermore, it provides insight in additional components required to complete photothermal reaction systems for continuous production (e. g., solar concentrators, sensors and artificial light sources). In addition, our review emphasizes the necessity of integrated collaboration between different research areas, like chemistry, material science, chemical engineering, and optics, to establish optimized systems and reach the full potential of this technology.

A nonmetallic plasmonic catalyst for photothermal CO2 flow conversion with high activity, selectivity and durability

The meticulous design of active sites and light absorbers holds the key to the development of high-performance photothermal catalysts for CO2 hydrogenation. Here, we report a nonmetallic plasmonic catalyst of Mo2N/MoO2-x nanosheets by integrating a localized surface plasmon resonance effect with two distinct types of active sites for CO2 hydrogenation. Leveraging the synergism of dual active sites, H2 and CO2 molecules can be simultaneously adsorbed and activated on N atom and O vacancy, respectively. Meanwhile, the plasmonic effect of this noble-metal-free catalyst signifies its promising ability to convert photon energy into localized heat. Consequently, Mo2N/MoO2-x nanosheets exhibit remarkable photothermal catalytic performance in reverse water-gas shift reaction. Under continuous full-spectrum light irradiation (3 W·cm-2) for a duration of 168 h, the nanosheets achieve a CO yield rate of 355 mmol·gcat-1·h-1 in a flow reactor with a selectivity exceeding 99%. This work offers valuable insights into the precise design of noble-metal-free active sites and the development of plasmonic catalysts for reducing carbon footprints.

Synergistic Modulation between Non-thermal and Thermal Effects in Photothermal Catalysis based on Modified In2O3

To promote the solar-energy cascade utilization, it is necessary to increase the thermal effect of irradiation in the catalytic reactions, while simultaneously augmenting the non-thermal effect, so as to fulfill photothermal coupling. Herein, the non-thermal and thermal effect of light radiation on the surface of In2O3-based catalysts are explored and enhanced by the modification of transition metals Fe and Cu. Optical characterizations combined with water-splitting experiments show that Fe doping greatly broadens the radiation response range and enhances the absorption intensity of semiconductors' intrinsic portion, and Cu doping facilitates the absorption of visible-infrared light. The concurrent incorporation of Fe and Cu offers synergistic benefits, resulting in improved radiation response range, carrier separation and migration, as well as higher photothermal temperature upon photoexcitation. Collectively, these advantages comprehensively enhance the photothermal synergistic water-splitting reactivity. The characterizations under variable temperature conditions have demonstrated that the reaction temperature exerts a significant influence on the process of radiation absorption and conversion, ultimately impacting the non-thermal effect. The results of DFT calculations have revealed that the increasing temperature directly impacts the chemical reaction by reducing the energy barrier associated with the rate-determining step. These findings shine new light on the fundamental mechanisms underlying non-thermal and thermal effect, while also imparting significant insights for photo-thermal-coupled catalyst designing.