CO2 Photoreduction Research Articles

Strain-Induced Self-Assembly at Interface of Two-Dimensional Heterostructures Boosts CO2 Reduction to Methanol by H2O.

CO2 conversion with pure H2O into CH3OH and O2 driven by solar energy can supply fuels and life-essential substances for extraterrestrial exploration. However, the effective production of CH3OH is significantly challenging. Here we report an organozinc complex/MoS2 heterostructure linked by well-defined zinc-sulfur covalent bonds derived by the structural deformation and intensive coupling of dx2-y2(Zn)-p(S) orbitals at the interface, resulting in distinctive charge transfer behaviors and excellent redox capabilities as revealed by experimental characterizations and first-principle calculations. The synthesis strategy is further generalized to more organometallic compounds, achieving various heterostructures for CO2 photoreduction. The optimal catalyst delivers a promising CH3OH yield of 2.57 mmol gcat-1 h-1 and selectivity of more than 99.5%. The reverse water gas shift mechanism is identified for methanol formation. Meanwhile, energy-unfavorable adsorption of methanol on MoS2, where the photogenerated holes accumulate, ensures the selective oxidation of water over methanol.

Harnessing Photo‐to‐Thermal Conversion in Sulfur‐Vulcanized Mxene for High‐Efficiency Solar‐to‐Carbon‐Fuel Synthesis

AbstractHarnessing solar energy for the conversion of CO2 into value‐added chemicals and fuels represents a promising strategy for sustainable development. Photo‐to‐thermal (PTT) conversion, an often‐underestimated factor, offers a remarkable approach to enhance the photocatalytic transformation of CO2, by reducing the activation energy of catalytic reactions and accelerating reaction kinetics. In order to achieve a higher energy return on investment (EROI), in this study, a sulfur‐vulcanized, multi‐layer Ti3C2 MXene is unveiled, capable of efficient sunlight‐driven CO2 photoreduction, by capitalizing on PTT conversion across the full visible‐to‐near‐infrared (NIR) spectrum. The vulcanization strategy is pivotal here, as it not only introduces an abundance of reactive sites but also extends the NIR response (peaking at 1095 nm) of MXene. The resulting rapid PTT and synergistic photo‐thermal‐catalytic CO2 reduction constitute a significant advance in this area, where CH4 (12.03 mmol g−1 h−1) and C2H4 (3.55 mmol g−1 h−1) yields are achieved with a C2+ selectivity of 29.76% under concentrated natural sunlight. This work sets a new benchmark for EROI with an average solar‐to‐carbon‐fuel (STF) conversion efficiency greater than 0.045%.

Photocatalytic CO2 reduction to syngas using nickel phosphide-loaded CdS under visible light irradiation

Photocatalytic CO2 reduction is a sustainable pathway to produce syngas (H2 + CO), which is a key feedstock for the production of several important liquid fuels on the industrial scale. However, achieving an appropriate tunable ratio of H2:CO in syngas for commercial purposes is a challenging task. In this work, we present a low-cost and non-noble metal, phosphide-based co-catalyst—Ni2P-loaded cadmium sulfide (CdS) photocatalyst system, for photocatalytic CO2 reduction. As a co-catalyst, Ni2P fosters an efficient charge separation of photoexcited charges generated in the CdS production of syngas. In total, 3 wt.% Ni2P/CdS exhibited exceptional performance of 50.6 µmol g−1 h−1 in the CO evolution rate and 115 µmol g−1 h−1 in the H2 evolution rate, with a syngas composition varying from 2 to 4 in the H2:CO ratio. Furthermore, first-principles density functional theory calculations were performed to study the surface energetics of the catalyst system and the results are found to be consistent with our experimental findings. Indeed, they establish that the composite favors CO2 photoreduction into syngas more efficiently than pure surfaces.

Tailoring CuNi heteronuclear diatomic catalysts: Precision in structural design for exceptionally selective CO2 photoreduction to ethanol

Tailoring CuNi heteronuclear diatomic catalysts: Precision in structural design for exceptionally selective CO2 photoreduction to ethanol

High-Volumetric Density Atomic Cobalt on Multishell ZnxCd1-xS Boosts Photocatalytic CO2 Reduction.

The volumetric density of the metal atomic site is decisive to the operating efficiency of the photosynthetic nanoreactor, yet its rational design and synthesis remain a grand challenge. Herein, we report a shell-regulating approach to enhance the volumetric density of Co atomic sites onto/into multishell ZnxCd1-xS for greatly improving CO2 photoreduction activity. We first establish a quantitative relation between the number of shell layers, specific surface areas, and volumetric density of atomic sites on multishell ZnxCd1-xS and conclude a positive relation between photosynthetic performance and the number of shell layers. The triple-shell ZnxCd1-xS-Co1 achieves the highest CO yield rate of 7629.7 μmol g-1 h-1, superior to those of the double-shell ZnxCd1-xS-Co1 (5882.2 μmol g-1 h-1) and single-shell ZnxCd1-xS-Co1 (4724.2 μmol g-1 h-1). Density functional theory calculations suggest that high-density Co atomic sites can promote the mobility of photogenerated electrons and enhance the adsorption of Co(bpy)32+ to increase CO2 activation (CO2 → CO2* → COOH* → CO* → CO) via the S-Co-bpy interaction, thereby enhancing the efficiency of photocatalytic CO2 reduction.

Effects of nanosized Au on the interface of zinc phthalocyanine/TiO2 for CO2 photoreduction

Effects of nanosized Au on the interface of zinc phthalocyanine/TiO2 for CO2 photoreduction

Constructing Co and Zn atomic pairs in core-shell Co3S4/NC@ZnS/NC derived from MOF-on-MOF nanostructures for enhanced photocatalytic CO2 reduction to C2H4

Herein, a core-shell structured Co3S4/NC@ZnS/NC heterojunction has been constructed via elaborately synthesizing metal-organic framework (MOF)-on-MOF precursors (ZIF-67@ZIF-8) and following controlled carbonization-sulfidation processes. The developed Co3S4/NC@ZnS/NC achieves higher performances for CO2 photoreduction with water vapor towards CO (28.44 μmol g−1 h−1), CH4 (1.93 μmol g−1 h−1) and C2H4 (12.23 μmol g−1 h−1) in a continuous-flow condition under visible-light irradiation, which are significantly superior than those of Co3S4/NC and ZnS/NC. 13CO2 isotope tracer analysis verifies that CO, CH4 and C2H4 originate from the carbon source of CO2. Experiments and DFT calculations confirm that constructing an electron transport layer (ZnS/NC) in Co3S4/NC@ZnS/NC can contribute to a feasible channel for the enhanced separation and transfer of charge carriers. In heterojunction, non-bonding Co and Zn atomic pairs as adsorption sites synergistically participate in the CO2 activation through the unique electron transport channel and acquire the lower energy barriers of COOH* formation. Moreover, in situ DRIFTS reveals the key intermediates and possible conversion pathways to main products. This work presents an attractive strategy to construct dual MOFs-derived metal sulfide heterojunctions for high-performance CO2 conversion.

Metal–oxygen hybridization in Agcluster/TiO2 for selective CO2 photoreduction to CH4

Selective photocatalytic reduction of CO2 to CH4 is one of the most efficient ways to achieve carbon neutralization. However, the formation of methane remains a challenge due to the slow multiple-proton-coupled electron transfer process and the involvement of various C1 intermediates. Herein, an Agcluster/TiO2 catalyst with Ag-O hybridization was synthesized by supporting Ag clusters on anatase phase TiO2 microspheres for photocatalytic CO2 methanation. The Agcluster/TiO2 sample presents an electron selectivity of 86 % for CH4 production with a yield of 25.25 μmol g–1 h−1. Mechanistic study reveals that Ag clusters accelerate the separation and migration of photogenerated carriers, and enhance the adsorption of CO2. Moreover, the Ag-O hybridization promotes the multiple-proton–electron coupling transfer process by effectively stabilizing intermediates and facilitating *CO hydrogenation to *CHO, resulting in selective CO2 reduction to CH4. This work provides a new insight into the development of selective photocatalytic conversion of CO2 to methane by constructing supported cluster catalysts.

An indirect Z-scheme heterostructure of nano-gold layer immobilized Cu-Al-doped SrTiO3 and CoOx-WO3 for photocatalytic CO2 reduction

Perovskite oxides have emerged as promising photocatalysts for CO2 reduction to valuable chemicals and fuels. However, conventional perovskite oxide photocatalysts often suffer from inefficient charge separation and bulk charge recombination, negatively impacting overall photoactivity. In this work, we present a novel immobilized perovskite oxide-based photocatalyst sheet featuring an indirect Z-scheme heterostructure composed of Cu-loaded Al-doped SrTiO3 (Cu-ASTO) and CoOx-loaded WO3 (CoOx-WO3) with an ultrathin (20 nm) gold interlayer serving as a conductive bridge. We tested this photocatalyst sheet in a sealed reactor containing a CO2-saturated aqueous solution of 0.1 M NaHCO3 and a side window to allow irradiation. Under irradiation with a 300 W Xe lamp, the Cu-ASTO/Au/CoOx-WO3 immobilized photocatalyst sheet produced methane (CH4) at a rate of 2.676 µmol cm-2 h−1 and methanol (CH3OH) at 0.517 µmol cm-2 h−1. We attribute the superior activity of this catalyst to the all-solid-state indirect Z-scheme heterostructure that greatly extends the lifespan of photoinduced charge carriers and enhances the CO2 photoconversion reaction. In experiments conducted outside, we demonstrated the immobilized photocatalyst's performance under natural sunlight, producing CH4 at 0.307 µmol cm-2 h−1 and CH3OH at 0.069 µmol cm-2 h−1. This work provides design ideas for developing robust immobilized photocatalyst systems for the scalable operation of the CO2 photoreduction process and broadening the scope of applications for perovskite heterostructure photocatalysts.

NH2-UiO-66 modification BiOBr enhancement photoreduction CO2 to CO

As a typical semiconductor catalyst, BiOBr has an advisable bandgap, superior light absorption properties, and a unique laminated structure. However, the slow electron-hole separation rate results in poor CO2 reduction performance. To enhance the photocatalytic efficiency of BiOBr, this study constructs BiOBr heterojunctions with Lewis basic groups by loading NH2-UiO-66 on BiOBr. The BiOBr/NH2-UiO-66 heterojunction have been built and possess stronger light response, larger specific surface area and electron-hole separation efficiency compared to pure BiOBr and NH2-UiO-66. The optimal BiOBr/NH2-UiO-66 displays that the CO yield is 9.19 μmol g-1h−1, which is 4 times higher than pure BiOBr.

Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3.

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Effect of the Ti content and pore size of mesoporous catalysts on CO2 photoreduction

The photocatalytic conversion of CO2 into chemicals and fuels is a promising approach for reducing atmospheric CO2 and addressing energy demands. This study investigates the impact of titanium (Ti) content and pore size in mesoporous silica on CO2 photoreduction (CO2PR) efficiency. Ordered mesoporous silica with a large surface area and stability is used as a matrix for Ti dispersion. Two sets of photocatalysts with varying Ti contents and pore sizes are synthesized and assessed for their microstructures, photoelectric properties, and CO2PR efficiency in both solid–gas and liquid–gas modes. The results reveal that photocatalysts with only 3.0 wt% Ti perform comparably to commercial TiO2 (P25) and can be recycled and reused. Moreover, an enhancement in photocatalytic activity with increasing pore sizes of the photocatalysts is observed. Notably, a photocatalyst with 3.0 wt% Ti and about 8 nm pore size significantly outperforms P25, producing much higher CH4, CO, and CH3OH yields. These findings are crucial for optimizing photocatalyst efficiency and are applicable across various compositions.

Engineering NH2‐Cu‐NH2 Triple‐atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3

AbstractSelective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C−C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal–organic framework UiO‐66‐NH2 for selective overall photo‐reduction of CO2 into acetone. The Cu2+ site in well‐modified CuN2O2 units served as a trapping site to capture electrons via efficient electron‐hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*‐CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat−1 h−1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple‐atomic sites to producing C3 product from photosynthesis with water.

Boosted Sacrificial-Agent-Free Selective Photoreduction of CO2 to CH3OH by Rhenium Atomically Dispersed on Indium Oxide.

Solar-energy-driven photoreduction of CO2 is promising in alleviating environment burden, but suffers from low efficiency and over-reliance on sacrificial agents. Herein, rhenium (Re) is atomically dispersed in In2O3 to fabricate a 2Re-In2O3 photocatalyst. In sacrificial-agent-free photoreduction of CO2 with H2O, 2Re-In2O3 shows a long-term stable efficiency which is enhanced by 3.5 times than that of pure In2O3 and is also higher than those on Au-In2O3, Ag-In2O3, Cu-In2O3, Ir-In2O3, Ru-In2O3, Rh-In2O3 and Pt-In2O3 photocatalysts. Moreover, carbon-based product of the photoreduction overturns from CO on pure In2O3 to CH3OH on 2Re-In2O3. Re promotes charge separation, H2O dissociation and CO2 activation, thus enhancing photoreduction efficiency of CO2 on 2Re-In2O3. During the photoreduction, CO is a key intermediate. CO prefers to desorption rather than hydrogenation on pure In2O3, as CO binds to pure In2O3 very weakly. Re strengthens the interaction of CO with 2Re-In2O3 by 5.0 times, thus limiting CO desorption but enhancing CO hydrogenation to CH3OH. This could be the origin for photoreduction product overturn from CO on pure In2O3 to CH3OH on 2Re-In2O3. The present work opens a new way to boost sacrificial-agent-free photoreduction of CO2.

Boosted Sacrificial‐Agent‐Free Selective Photoreduction of CO2 to CH3OH by Rhenium Atomically Dispersed on Indium Oxide

AbstractSolar‐energy‐driven photoreduction of CO2 is promising in alleviating environment burden, but suffers from low efficiency and over‐reliance on sacrificial agents. Herein, rhenium (Re) is atomically dispersed in In2O3 to fabricate a 2Re‐In2O3 photocatalyst. In sacrificial‐agent‐free photoreduction of CO2 with H2O, 2Re‐In2O3 shows a long‐term stable efficiency which is enhanced by 3.5 times than that of pure In2O3 and is also higher than those on Au‐In2O3, Ag‐In2O3, Cu‐In2O3, Ir‐In2O3, Ru‐In2O3, Rh‐In2O3 and Pt‐In2O3 photocatalysts. Moreover, carbon‐based product of the photoreduction overturns from CO on pure In2O3 to CH3OH on 2Re‐In2O3. Re promotes charge separation, H2O dissociation and CO2 activation, thus enhancing photoreduction efficiency of CO2 on 2Re‐In2O3. During the photoreduction, CO is a key intermediate. CO prefers to desorption rather than hydrogenation on pure In2O3, as CO binds to pure In2O3 very weakly. Re strengthens the interaction of CO with 2Re‐In2O3 by 5.0 times, thus limiting CO desorption but enhancing CO hydrogenation to CH3OH. This could be the origin for photoreduction product overturn from CO on pure In2O3 to CH3OH on 2Re‐In2O3. The present work opens a new way to boost sacrificial‐agent‐free photoreduction of CO2.

Unravelling the effect of Ti3+/Ti4+ active sites dynamic on reaction pathways in direct gas-solid-phase CO2 photoreduction

Converting CO2 to CH4 by solar-powered catalysis involves complex steps that produce a range of by-products. Therefore, designing efficient heterostructures for a particular chemical synthesis is challenging. The optimisation of photocatalyst surfaces can achieve the desired CO2 photoreduction pathway. Herein, we developed TiO2/CdSe nanocrystals with both amorphous and crystalline TiO2 surfaces. In situ EXAFS analysis revealed that the amorphous surface contains abundant active Ti3+ sites, while the crystalline surface is limited. Moreover, the amorphous surface of TiO2/CdSe exhibits self-regenerating Ti3+ active sites, which enable a novel CH4 cycle. Density functional theory calculation showed that an amorphous structure enhances electron transfer and localisation to Ti3+, favouring CO2 adsorption. In situ DRIFTS analysis showed different CO2 to CH4 pathways on both surfaces. These results show the potential for enhanced photocatalytic CO2 reduction through surface engineering, which has far-reaching implications for sustainable energy conversion.

Ferroelectric Polarization and Single-Atom Catalyst Synergistically Promoting CO2 Photoreduction of CuBiP2Se6.

Further improving the activity and selectivity of photocatalytic CO2 reduction remains a challenge. Herein, we propose a new strategy for synergistically promoting photocatalytic CO2 reduction by combining two-dimensional (2D) ferroelectric polarization and single-atom catalysis. Our calculations showed that the ferroelectric polarization of CuBiP2Se6 provides the internal driving force for the separation and migration of photogenerated carriers, which provides a prerequisite for enhancing the photocatalytic efficiency. In addition, the introduction of single Ag atoms can act as an electron reservoir to significantly modify the bonding configurations on the surface through proper static electron transfer, thus effectively promoting the adsorption and activation of CO2 molecules. More importantly, we found that switching the ferroelectric polarization can synergistically optimize the limiting potential as well as control the final products. This study provides a new approach for enhancing the catalytic activity and selectivity of photocatalytic CO2 reduction.

Dipole increase synergistic frustrated Lewis pairs induced by Sn dopant boosts ultrathin layered bismuth oxychloride for CO2 photoreduction

Photocatalytic conversion of CO2 into valued chemicals is limited by the CO2 adsorption and activation capability on catalyst surface. In this work, Sn element was successfully doped in ultrathin BiOCl with oxygen vacancies. The dipole moment of catalyst efficient increased due to the Sn doping, leading to a stronger internal electric field. In addition, the surface frustrated Lewis pairs were simultaneously constructed near the oxygen vacancies due to Sn dopant. The formed region of frustrated Lewis pairs-oxygen vacancies as active sites enable an improved CO2 adsorption, and the enhanced internal electric field intensity promoted the charge carrier separation and transfer, leading to the enhanced CO2 reduction performances. This work provides light on enhancing internal electric field by increasing dipole moment and presents feasible tunability of catalytic active sites at atom-scale, providing fundamental insights for understanding of mechanism of element doping in catalyst for improving CO2 photoreduction performance.

The A-site and B-site regulation of LaCoO3 nanofiber based on electrospinning for boosting photocatalytic CO2 conversion

Photocatalytic CO2 reduction with perovskite can effectively address both energy and environmental issues. Nevertheless, it remains challenging to prepare photocatalysts with suitable hollow tubular structures in rational. Herein, the La1-xSrxCo1-δFeδO3 nanofiber with a hollow tubular structure was fabricated through an electrospinning method. The hollow nanofiber structure was constructed by doping Sr atoms in the A-site and Fe atoms in the B-site of LaCoO3 perovskite. The characterization of TEM proved that the hollow tubular structural La1-xSrxCo1-δFeδO3 nanofiber exhibited an external diameter of about 95 nm and an internal diameter of about 50 nm. The hollow tubular structural La1-xSrxCo1-δFeδO3 nanofiber showed superior carrier separation ability which could exhibit significant advantages for photocatalytic CO2 reduction. The CH3OH generation rate over the optimized La0.8Sr0.2Co0.7Fe0.3O3 nanofiber could reach 5.25 µmol⋅g−1⋅h−1. This work highlighted an electrospinning strategy to build a hollow tubular structural La1-xSrxCo1-δFeδO3 nanofiber for enhancing photoreduction CO2.

Efficient Photoreduction of CO2 to CO with 100% Selectivity by Slowing Down Electron Transport.

It remains challenging to obtain a single product in the gas-solid photocatalytic reduction of CO2 because CO and CH4 are usually produced simultaneously. This study presents the design of the I-type nested heterojunction TiO2/BiVO4 with controllable electron transport by modulating the TiO2 component. This study demonstrates that slowing electron transport could enable TiO2/BiVO4-4 to generate CO with 100% selectivity. In addition, modifying TiO2/BiVO4-4 by loading a Cu single atom further increased the CO product yield by 3.83 times (17.33 μmol·gcat-1·h-1), while maintaining 100% selectivity for CO. Characterization and density functional theory (DFT) calculations revealed that the selectivity was mainly determined by the electron transport of the support, whereas CO2 was efficiently adsorbed and activated by the Cu single atom. Such a two-step regulation strategy of combining heterojunction with single atom enhances the possibility of simultaneously obtaining high selectivity and high yield in the photocatalytic reduction of CO2.