CO2 Reduction Research Articles

Co-In Bimetallic Hydroxide Nanosheet Arrays With Coexisting Hydroxyl and Metal Vacancies Anchored on Rod-Like MOF Template for Enhanced Photocatalytic CO2 Reduction.

Layered double hydroxides (LDHs) can serves as catalysts for CO2 photocatalytic reduction (CO2PR). However, the conventionally synthesized LDHs undergo undesired aggregation, which results in an insufficient number of active sites and limits the desirable electron transfer required for CO2PR. The metal-organic framework (MOF) template-grown LDHs demonstrate excellent promise for exploiting the strengths of both MOFs and LDHs. Herein, the in situ growth of MIL-68(In)-NH2 MOF-templated Co-In bimetallic catalyst (CoIn-LDH/MOF) having an ultrathin nanosheet morphology on the preserved rod-like MOF template is demonstrated. Compared to the conventionally grown bimetallic LDH (CoIn-LDH), CoIn-LDH/MOF not only exposes more active sites but also possesses hydroxyl vacancies (VOH) and Co vacancies (VCo). Thus, CoIn-LDH/MOF performs a higher CO generation rate of 2320µmol g-1 h-1 during CO2PR, demonstrating improved activity and selectivity than those in CoIn-LDH. Experiments coupled with calculations reveal that the CoIn-LDH/MOF-driven CO2PR follows the *COOH pathway. The lower energy barriers for the formation of *COOH and CO(g) can be attributed to the coexistence of VOH and VCo in CoIn-LDH/MOF, effectively promoting charge transfer and enhancing CO2PR performance. This study provides a new strategy to obtain high-performant LDH-based catalysts with improved morphology.

Constructing solid waste-derived carbon fiber with self-doped Ti3+/TiO2 (SWCFs/Ti3+/TiO2) heterojunction for photocatalytic CO2 reduction

Constructing solid waste-derived carbon fiber with self-doped Ti3+/TiO2 (SWCFs/Ti3+/TiO2) heterojunction for photocatalytic CO2 reduction

Tandem Electroreduction of CO2 to C2+ Products based on M-SACs/Cu Catalyst.

Electrochemical CO2 reduction reaction (ECO2RR) is considered a highly promising method to produce high-value chemicals and fuels, contributing significantly the artificial carbon balance. Cu species exhibit a distinct role in the formation of C2+ products characterized by enhanced energy density. The limited selectivity of C2+ products, along with the inferior stability, and high overpotential demonstrated by single-component Cu catalysts, hinders their applicability in industrial-scale production. The implementation of a tandem strategy, which involves coupling the CO2-to-CO pathway using metal single-atom catalysts (M-SACs), etc., with the CO-to-C2+ conversion on Cu species, represents a novel approach for the efficient generation of C2+ products. Given the high cost and restricted availability of noble metals, M-SACs have attracted substantial interest in tandem systems. The systematic analysis of the design principles and structure-activity relationship is essential for the advancement of M-SACs/Cu-based tandem catalysts. Here we first introduce various prevalent design strategies of M-SACs/Cu-based tandem catalysts for ECO2RR and then systematically summarize the latest advancements of M-SACs/Cu-based tandem system, encompassing metal-organic frameworks/Cu (MOFs/Cu), covalent organic frameworks/Cu (COFs/Cu), and nitrogen-doped carbon support transition metal single atomic materials/Cu (M-N-C/Cu). Lastly, we discuss the challenges and opportunities with the design and construction of M-SACs/Cu-based tandem catalysis for ECO2RR.

Ligand-Dependent Intracluster Interactions in Electrochemical CO2 Reduction Using Cu14 Nanoclusters.

The electrochemical CO2 reduction reaction (CO2RR) has been extensively studied because it can be leveraged to directly convert CO2 into valuable hydrocarbons. Among the various catalysts, copper nanoclusters (Cu NCs) exhibit high selectivity and efficiency for producing CO2RR products owing to their unique geometric/electronic structures. However, the influence of protective ligands on the CO2RR performance of Cu NCs remains unclear. In this study, it is shown that different thiolate ligands, despite having nearly identical geometries, can substantially affect the electrochemical stability of Cu14 NCs in the CO2RR. Notably, Cu14 NCs protected by 2-phenylethanethiolate exhibit greater stability and achieve a relatively higher selectivity (≈40%) for formic acid production compared with the cyclohexanethiolate-protected counterpart. These insights are crucial for designing Cu NCs that are both stable and highly selective, enhancing their efficacy for electrochemical CO2 reduction.

Monodisperse Cu Nanoparticles Supported on a Versatile Metal–Organic Framework for Electrocatalytic Reduction of CO2

Monodisperse Cu Nanoparticles Supported on a Versatile Metal–Organic Framework for Electrocatalytic Reduction of CO₂

Photovoltaic Cells and Scintillators Towards Carbon Footprint Reduction: Advantages and Challenges for Ecological Safety

The main goal of this review paper is to show the advantages and challenges of photovoltaic cells/modules/panels and scintillators towards carbon footprint reduction for ecological safety. Briefly, the various types of solar-driven CO2 conversion processes are shown as a new concept of CO2 reduction. The health toxicity and environmental effects of scintillators, along with risks associated with use and disposal, are presented, taking into consideration inorganic and organic materials. Factors affecting the durability and lifespan of scintillators and the carbon footprint of solar cell production are analysed, considering CO2 emission. Moreover, the technology of recycling photovoltaic modules and scintillators, along with a SWOT analysis of scintillation material toxicity, is presented to find the best solutions for clean technology and ecological safety. Finally, we offer recommendations for the areas where the most significant reductions in CO2 emissions are expected to be implemented in the future of green energy in industry, including ESG strategies.

Fast Seawater Desalination Integrated with Electrochemical CO2 Reduction.

Coupling desalination with electrocatalytic reactions is an emerging approach to simultaneously addressing freshwater scarcity and greenhouse gas emissions. However, the salt removal rate in such processes is slow, and the applicable water sources are often limited to those with high salt concentrations. Herein, we show high-performance electrocatalytic desalination by coupling with electrochemical CO2 reduction using a carbon catalyst. A ZIF-8-derived carbon catalyst embedded with Cu nanoparticles delivers a high Faradaic efficiency of 94.3% for CO production at 288 μmol cm-2 h-1. The efficient CO2 electroreduction generates high current densities, which drive fast salt ion transfer across ion exchange membranes. The integrated device enables one of the quickest salt removal rates of 1043.49 μg cm-2 min-1 among various desalination methods. Drinking water can be obtained with an ion removal rate of 99% when natural seawater is used as the water source.

Evolutionary trends and photothermal catalytic reduction performance of carbon dioxide by MOF-derived MnOx

Metal oxide catalysts derived from MOFs can inherit the excellent performance from their parent MOFs, possess abundant surface defects and high stability, and have attracted widespread interest in multiphase catalysis. In this study, we used Mn-MOF as a precursor and systematically investigated the evolution of MnOx catalysts by setting different calcination temperatures and times. XRD, SEM, TEM, Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption analysis, XPS, H2-TPR, CO2-TPD, electrochemical characterization, and other methods were used to investigate the structural characteristics, microstructure, surface properties, and photoelectric properties of the catalysts. The catalytic performance of the catalysts was also investigated through photocatalytic carbon dioxide hydrogenation reduction tests. Research has shown that calcination temperature and time have a significant impact on the phase structure and surface properties of MnOx, and the physicochemical properties of derived MnOx can be controlled by controlling calcination temperature and time. Among them, MnOx-500 has a wider light absorption range, better electron transfer performance, richer oxygen vacancies, and excellent separation performance of photo generated charge carriers, resulting in higher photocatalytic CO2 hydrogenation and reduction performance. Its CO yield and selectivity reached 7420 μmol/g/h and above 99 %, respectively. This study provides valuable references for the preparation, optimization, and utilization in CO2 photothermal catalytic conversion of MnOx catalysts derived from MOFs.

Electric Field-assisted Photocatalytic Reduction of Carbon Dioxide over Titanium Dioxide: Influence of the Type and Strength of Electric Field

This study focuses on investigating the sole impact of an external electric field on the photocatalytic activity of TiO2-based materials. Typically, built-in electric fields are used to efficiently separate free energy carriers and improve the photocatalytic performance of semiconductors. The creation of such field requires modifications to the photocatalyst that alter various properties such as adsorption and optical characteristics. These modifications make it challenging to isolate and interpret the promotion effect associated with the electric field alone. The investigations were carried out in the gas-phase conditions in a specially constructed reactor equipped with two electrodes connected to a high – voltage that provides a field strength of up to 5.7·103 V/cm. The results showed that the effect of electric field promotion varied significantly depending on the properties of titanium dioxide, such as structure, adsorption, and presence of impurities. The strength and the type (direct or alternating current) of the electric field also played a determining role. The greatest promoting effect was observed for rutile, the photocatalytic activity of which under an electric field increased threefold in the process of reduction of CO2 with water vapor.Graphical

Regulating Interfacial Hydrogen-Bonding Networks by Implanting Cu Sites with Perfluorooctane to Accelerate CO2 Electroreduction to Ethanol.

Efficient CO2 electroreduction (CO2RR) to ethanol holds promise to generate value-added chemicals and harness renewable energy simultaneously. Yet, it remains an ongoing challenge due to the competition with thermodynamically more preferred ethylene production. Herein, we presented a CO2 reduction predilection switch from ethylene to ethanol (ethanol-to-ethylene ratio of ~5.4) by inherently implanting Cu sites with perfluorooctane to create interfacial non-covalent interactions. The 1.83%F-Cu2O organic-inorganic hybrids (OIHs) exhibited an extraordinary ethanol faradaic efficiency (FEethanol) of ∼55.2%, with an impressive ethanol partial current density of 166 mA cm-2 and excellent robustness over 60 hours of continuous operation. This exceptional performance ranks our 1.83%F-Cu2O OIHs among the best-performing ethanol-oriented CO2RR electrocatalysts. Our findings identified that C8F18 could strengthen the interfacial hydrogen bonding connectivity, which consequently promotes the generation of active hydrogen species and preferentially favors the hydrogenation of *CHCOH to *CHCHOH, thus switching the reaction from ethylene-preferred to ethanol-oriented. The presented investigations highlight opportunities for using noncovalent interactions to tune the selectivity of CO2 electroreduction to ethanol, bringing it closer to practical implementation requirements.

Zr-MOF/MXene composite for enhanced photothermal catalytic CO2 reduction in atmospheric and industrial flue gas streams

In this study, a novel composite was engineered by integrating Zr-MOF (NH2-UIO-66) with MXene layers through electrostatic self-assembly. Under simulated sunlight and at 80 °C, this composite material achieved nearly complete conversion of low-concentration atmospheric CO2 to CO and CH4 without additional sacrificial agents or alkaline absorption liquids, marking one of the few reports demonstrating near-complete reduction of low-concentration CO2 directly from the air. For high-concentration CO2 in industrial flue gas, the composite utilized residual heat at 80 °C without additional energy input, exhibiting excellent CO2 reduction efficiency with CO and CH4 production rates of 127 μmol·g-1·h-1 and 330 μmol·g-1·h-1, respectively, resulting in a total production rate 4.76 times higher than that in the air. Compared to most reports on thermocatalytic CO2 reduction (>300 °C), this material shows significant advantages below 100 °C. The performance improvement is attributed to the introduction of Zr-MOF, which provides additional active sites and reduces activation energy. Additionally, the localized surface plasmon resonance (LSPR) effect of MXene facilitates the migration of thermal charge carriers to Zr4+ sites within the MOF. Density Functional Theory (DFT) calculations validate these findings. Overall, Zr-MOF/MXene composite holds potential for reducing CO2 in air and industrial settings, advancing energy conversion and environmental management.

Electrochemical CO2 reduction to syngas on copper mesh electrode: Alloying strategy for tuning syngas composition

Electrochemical CO2 reduction to synthetic fuels and commodity chemicals using renewable energy offers a promising approach to mitigate CO2 emissions and alleviate energy crisis. Copper-based catalysts show potential for electrochemical CO2 reduction applications, while they face the key challenges of high potential, sluggish kinetics, and poor selectivity. In this work, Cu-Zn, Cu-Co, Cu-Cd, and Cu-In bimetallic catalysts are synthesized via the electrodeposition method for electrochemical CO2 reduction to syngas with adjustable CO/H2 ratios. The bimetallic catalysts are characterized using various techniques to reveal their crystalline structures, morphologies, and elemental compositions. The structure-property-activity relationships of these catalysts are investigated to identify optimal candidates for electrochemical CO2 reduction applications. The findings reveal that the bare Cu mesh catalyst exhibits poor CO2 reduction activity, and the products are dominated by hydrogen evolution reaction (HER). The bimetallic catalysts exhibit improved CO2 reduction performance, with the Cu-Zn and Cu-Cd catalysts showing excellent activity, and the CO/H2 ratio in syngas can be tuned over a wide range by adjusting the applied potential. The Cu-Zn and Cu-Cd catalysts demonstrate outstanding performance with Faradic efficiencies of ∼90 % and ∼80 % towards syngas production with CO/H2 ratios of ∼2.0 and ∼1.5 at −0.81 and −1.01 V vs. RHE, respectively, making the produced syngas suitable for various industrial applications. Stability tests over 450 min show that the Cu-Zn and Cu-Cd catalysts maintain stable catalytic activity, syngas selectivity and CO/H2 ratio, making them robust candidates for syngas production. The results will provide valuable insights into the design of robust catalysts for electrochemical CO2 reduction, offering a promising path toward sustainable syngas production.

Experimental investigation of fuel conversion characteristics during co-combustion of solid recovered fuel and coal in a 1 MWth circulating fluidized bed reactor

This study presents experimental results on co-combustion of hard coal and solid recovered fuel (SRF) conducted in a circulating fluidized bed (CFB) reactor with an internal diameter of 0.59 m, a height of 8.6 m, and a thermal load of 1 MWth. The high flexibility of the test facility enables testing of a variety of input materials under changing test conditions. The combustion of various fuel mixes ranging from 100 % hard coal to 100 % waste was tested to assess the impact of varying fuel ratios on the overall combustion process. As the proportion of SRF increased, a reduction in reactor differential pressure and particle density was observed. Moreover, combustion shifts to higher parts in the reactor when the share of SRF is increased. To further investigate the combustion conditions inside the reactor, three in-bed gas measurements were conducted, capturing the horizontal gas profiles of CO2, O2, and CO. An increase in SRF content led to elevated CO and O2 levels, alongside a reduction in CO2, indicating an upward shift in the combustion zone. The behavior is attributed to the higher volatile content of SRF, which is in this experiment roughly 2.5 times the share of volatiles in hard coal and the lower bulk density of SRF. The study concludes by proposing potential strategies for reducing the impact of high SRF content on combustion conditions.

Mechanism of biochar-Cu-based catalysts construction and its electrochemical CO2 reduction performance

Electrochemical CO2 reduction can convert CO2 into high-value-added products for special forms of energy storage and efficient carbon utilization for renewable electricity. To investigate the influence of biochar-Cu-based catalysts properties on electrochemical CO2 reduction performance, Cu is loaded onto rice husk-based biochar by impregnation method combined with pyrolysis and calcination in this study. The three synthesized biochar-Cu-based catalysts are tested for activity and electrochemical CO2 reduction performance in Flow Cell. The results show that biochar's properties, such as its high specific surface area, rich pore structure, and adjustable pore structure, provide sufficient sites for CO2 reduction. Urea can relatively increase the copper loading by 44 %, but it will also increase the clustering of copper. In the reduction performance test, the current density of char-Cu-700 is 2.08 times higher than that of char-Cu and 1.45 times higher than char-Cu-N at a reduction potential of -0.45 (V vs. RHE). The current density enhancement of the catalyst loaded on biochar with Cu particle size of 10 nm is about 50 % higher than that of the catalyst with a particle size of 20 nm. It indicates that the smaller the particle size of Cu at the nanoscale, the lower the average coordination of surface atoms and the greater the catalyst's reactivity. This study provides novel ideas for synthesizing biochar-Cu-based catalysts, lays part of the theoretical foundation for using biochar-Cu-based catalysts for electrochemical CO2 reduction, and provides experimental support for optimizing the catalyst structure.

An integrated solution of energy storage and CO2 reduction: Trans-critical CO2 energy storage system combining carbon capture with LNG cold energy

An integrated solution of energy storage and CO2 reduction: Trans-critical CO2 energy storage system combining carbon capture with LNG cold energy

Targeting active sites nickel-porphyrin over BiOBr nanosheets with excellent charge separation for accelerated photoreduction reactions

The energy crisis and environmental pollution severely constrained the sustainable development of society. Herein, nickel-porphyrin active sites have been integrated over BiOBr for enhanced photocatalytic CO2 reduction and Cr(VI) removal. The optimized NiTMCPP/BiOBr-2 photocatalyst exhibits CO generation rate of 14.14 μmol g−1 under irradiation for 5h, which is around 2 times compared with BiOBr. Meanwhile, Cr(VI) removal efficiency over NiTMCPP/BiOBr-2 is 97.72% under visible light irradiation for 40min, which shows enhanced photoreduction ability compared with BiOBr (77.31%). Numerous experimental results indicate that the improved photocatalytic activity for NiTMCPP/BiOBr-2 is mainly owing to the enhanced transport efficiency of photoinduced carriers after the loading of Ni-porphyrin. Especially, the central Ni2+ active site of porphyrin can accept excitation electrons, thus enhancing photoreduction performance. Furthermore, the mechanisms for photocatalytic CO2 and Cr(Ⅵ) reduction were further discussed via in-situ FT-IR and capture experiments. This work gives a promising way to design hybrid photocatalysts for energy conversion and environmental treatment.

Two-Dimensional MXene-Based Functional Composites for Photocatalysts: Current Status and Perspectives

Abstract: MXenes, as novel two-dimensional (2D) transition metal carbides, nitrides or carbonitrides, have excellent metal conductivity, high carrier mobility, and surface-terminated groups regulated band structure. It can be thus used as a cocatalyst in photocatalytic systems to improve the photocatalytic properties. This review represented recent research progress on the controllable construction of MXene-based functional composites with zero-dimensional (0D), one-dimensional (1D), 2D, and three-dimensional (3D) semiconductor photocatalysts and their applications for photocatalysts. Extensive information related to 2D MXene-Based composites for photocatalysts and their associated patents were collected. The construction methods and photocatalytic enhancement mechanisms of 2D MXene-based composite photocatalysts were given. Due to their excellent physical and chemical properties, 2D MXene composites have been widely used in pollutant removal, hydrogen production, CO2 reduction, and nitrogen fixation. Through the construction of 2D MXene-based functional composite photocatalysts with novel structures and excellent performance, it provides a new perspective for the design and construction of high-efficiency photocatalysts. The future research directions of MXene-based composite photocatalysts was proposed.

CO2 to fuel: Role of polymer electrolytes on efficiency and selectivity

Global primary energy consumption, which heavily depends on fossil fuels, is on track for depletion, with projections suggesting exhaustion by 2100. This trajectory is further compounded by the persistent rise in atmospheric CO2 levels, currently at 420 ppm, which significantly contributes to climate change and its detrimental environmental consequences. To address this urgent challenge, various strategies have been proposed, including CO2 capture and storage, as well as its conversion into usable fuels. Leveraging the abundance of CO2 as a carbon source, coupled with sustainable energy resources such as solar, wind, and thermal energy, holds promise for generating value-added goods while mitigating environmental harm. This review focuses on the electrochemical reduction of CO2, presenting a dual-pronged approach aimed at decreasing atmospheric CO2 levels. The imperative to simultaneously combat declining atmospheric CO2 concentrations and advance cleaner, sustainable energy sources underscores the urgency of this endeavor. Specifically, we highlight the pivotal role of diverse polymer electrolytes, encompassing cation, anion, and bipolar membranes, in facilitating electrochemical CO2 reduction. Exploring the impact of functional groups within these membranes on CO2 reduction reaction provides insights into potential advancements in synthesis of eco-friendly fuel from conversion of CO2.

Juncus effuses biochar-assisted preparation of oxygen vacancies-rich BiOCl for photocatalytic degradation of pollutants and CO2 reduction

BiOCl has attracted widespread attention due to its unique layered structure and excellent photocatalytic performance. However, the intense application of BiOCl is limited by its wide bandgap and high recombination of e-/h+ pairs. In this paper, juncus effuses biochar/BiOCl (BC/BiOCl) photocatalysts with tunable oxygen vacancies (OVs) were successfully constructed by adjusting the ratio of biochar (BC) to BiOCl using juncus effuses biochar as a carbon source. Addition of BC affects the crystal growth of BiOCl, constructing of OVs. The synergistic effect of BC and OVs improves the photogenerated charge pairs separation efficiency of the photocatalyst and promotes the production of reactive oxygen species (·OH, ·O2-). Under a 300W xenon lamp irradiation, the degradation rate constant of rhodamine B (RhB) and tetracycline hydrochloride (HCl-TC) on the 0.5% sample (mass ratio of BC/BiOCl is 0.5%) is 3.53 times and 3.20 times of that on the reference BiOCl, respectively. In addition, photocatalytic materials prepared also show excellent versatility. After a 300W xenon lamp irradiation for 4h, the average conversion of CO2 on the 0.5% sample is 2.47 times of that on the reference BiOCl. This work provides a feasible strategy for rationally regulating the level of OVs.

Electronic interactions between SnO2 crystals and porous N-doped carbon nanoflowers accelerate electrochemical reduction of CO2 to formate

The electrochemical carbon dioxide reduction reaction (CO2RR) to formic acid or formate is a highly effective approach for achieving carbon neutrality. However, multiple proton-coupling-electronic processes and the instability of the catalysts caused by surface poisoning greatly limit the overall efficiency of CO2RR to formate. Here, a facile method was developed to anchor ∼2.60 nm SnO2 crystals onto porous N-doped carbon nanoflowers (SnO2@N-GPC) for high-efficiency formate production. The maximum Faraday efficiency (FE) of the SnO2@N-GPC reached 96.3 % at −1.2 V vs reversible hydrogen electrode (RHE) and was more than 80.0 % in the potential region from −1.0 to −1.5 V vs RHE with ten hours of operating stability. The experimental results and density functional theory (DFT) calculations demonstrated that the electronic interactions between SnO2 and N-GPC precipitated by electron transfer from SnO2 to N-GPC at the interface improved the phase stability of the SnO2@N-GPC, which improved its stability for the CO2RR. Furthermore, the electronic interactions enhanced the adsorption of CO2 on the catalyst, accelerating the rate of the formation of key intermediates, and reducing the energy barrier of the rate-limiting step for generating formate. This study provides an efficient strategy for developing highly active and stable non-precious metal catalysts for the conversion of CO2 to high-value chemicals.