Targeted H2O activation to manipulate the selective photocatalytic reduction of CO2 to CH3OH over carbon nitride supported cobalt sulfide

Mosallanezhad A., Wei C., Ahmadian Koudakan P., Fang Y., Niu S., Bian Z., Liu B., Huang T., Pan H., Wang G.

Despite the significant role of single atoms during the hydrogen evolution reaction (HER), the underlying nature of the synergetic effect between substrates and single atom is still unclear. Herein, through anchoring Pt single atoms on cobalt sulfide support (Pt@CoS), the roles of Pt single atoms and the substrate for alkaline HER catalysis are unfolded. Electrochemical studies demonstrate the remarkable catalytic performance of Pt @CoS catalysts with a 45-fold increase in mass current density compared to the benchmark Pt/C at 100 mV. The DFT calculation unravels that the anchored Pt SAs on CoS enable more unhybridized d z 2 orbitals of surrounding cobalt sites through the interfacial synergetic effect, which benefits the water dissociation kinetics. Likewise, the Pt sites can also act as active sites to facilitate the subsequent H 2 formation, thus synergistically promoting the alkaline HER catalysis. This work highlights the importance of the synergies effect between single atoms and substrate for rational catalyst design. Pt single atom anchored on CoS could enable more unhybridized d z 2 orbitals of surrounding cobalt sites for water dissociation, while the Pt single atoms facilitate H 2 generation, thereby synergistically promoting the catalytic kinetics of alkaline HER. • Pt@CoS displays a 45-time increase in Pt mass current density compared to the benchmark Pt/C at 100 mA cm −2 . • Theoretical analysis unravels the synergistic effect resulting in more unhybridized d z 2 orbitals of Pt surrounded cobalt atoms. • Pt@CoS improves both the water dissociation and recombination step via an interfacial synergy.

An X., Tang Q., Lan H., Liu H., Yu X., Qu J., Lin H., Ye J.

Photoreduction of CO2 provides an appealing way to alleviate the energy crisis and manage the global carbon balance but is limited by the high activation energy and the rate-limiting proton transfer. We now develop a dual-site strategy for high-efficiency CO2 conversion through polarizing CO2 molecules at pyridine N vacancies and accelerating the intermediate protonation by protonated pyridine N adjacent to nitrogen vacancies on polymeric carbon nitride. Our photocatalysts with atomic-level engineered active sites manifest a high CO production rate of 1835 μmol g-1 h-1 , 183 times higher than the pristine bulk carbon nitride. Theoretical prediction and experimental studies confirm that such excellent performance is attributed to the synergistic effect between vacant and protonated pyridine N in decreasing the formation energy of the key *COOH intermediates and the efficient electron transfer relay facilitated by the defect-induced shallow trap state and homogeneous charge mediators.

Ma M., Chen J., Huang Z., Fa W., Wang F., Cao Y., Yang Y., Rao Z., Wang R., Zhang R., Zou Y., Zhou Y.

• Intermolecular hydrogen bond was formed between N-C@Co and H 2 O molecule. • Intermolecular hydrogen bond induced selective coupling of protons and CO 2. • N-C@Co with intermolecular hydrogen bond suppressed the desorption of CO. • The selective CH 4 generation from CO 2 was achieved over N-C@Co photocatalyst. Photocatalytic reduction of CO 2 with H 2 O to CH 4 is a promising route to migrate CO 2 emission and complete the carbon neutrality goal. Nevertheless, one of the biggest challenges for this elegant strategy is that the coupling of the protons and CO 2 to form CH 4 is fiercely competed with proton-proton coupling to form H 2 , leading to extremely low CH 4 selectivity. Herein, we designed and fabricated the nitrogen-doped carbon layers modified cobalt (N-C@Co) photocatalyst achieving the selective coupling of protons and CO 2 to CH 4 during photocatalytic reduction of CO 2 . The successful formation of intermolecular hydrogen bonds between the as-prepared N-C@Co and H 2 O molecule was found to suppress the mass transfer of the generated protons and promote the adsorption and activation of the CO 2 molecule. More crucially, it was conducive to suppressing the desorption of the CO intermediate, which was typically deemed as the decisive species for CH 4 generation. As a result, the H 2 selectivity (9.0 %) and activity (17.3 µmol g −1 ) of the as-prepared N-C@Co were reduced by a factor of 9.3 and 17.6, respectively, as compared to that of bulk Co. The CH 4 selectivity of N-C@Co was boosted 6.1 times from 13.3% of bulk Co to 81.3 % of N-C@Co with the generation rate of 155.7 μmol g −1 in 23 h. This work provides a new insight into the photocatalyst design for improving CH 4 selectivity and suppressing the competing H 2 and CO generation.

Li X., Wang Z., Zhang J., Dai K., Fan K., Dawson G.

The solar driven reduction of carbon dioxide (CO 2 ) to high value-added carbon based fuel is a promising solution to mitidate climate and energy problems, however, improving the adsorption and conversion efficiency of CO 2 in the photoreduction process still faces severe challenges. In this work, Cd 0·7 Zn 0·3 Se solid solution was prepared by cation exchange: selenium (Se) vacancies are produced during ion exchange, which promotes the unsaturated coordination of the surrounding metal atoms. The adsorption of diethylenetriamine (DETA) on the surface limits the growth of Cd x Zn 1- x Se crystallites, resulting in insufficient coordination of the surface atoms, which then become active adsorption sites. Furthermore, a heterojunction was formed with Cu 2 O@Cu to accelerate the separation and transfer of photo-induced carriers of Cd 0·7 Zn 0·3 Se, and the optimized Cd 0·7 Zn 0·3 Se/Cu 2 O@Cu (CZS/CC) step-scheme heterojunction exhibited a CO release activity of 50.5 μmol g −1 h −1 , which is 3.8 and 10.7 times higher than that of Cd 0·7 Zn 0·3 Se and Cu 2 O@Cu, respectively. This work is expected to open up new insight for the regulation of nanostructures and the design of selective catalysts. • Cd x Zn 1- x Se/Cu 2 O@Cu step-scheme heterostructures were fabricated. • >The heterostructures showed excellent photocatalytic CO 2 reduction activity and stability. • Step-scheme heterostructures promoted the separation of carries dramatically. • >Step-scheme electron transport effectively suppressed the photocorrosion.

Yang H., Dai K., Zhang J., Dawson G.

Inorganic-organic hybrid materials are promising for application in the field of photocatalysis because of their excellent properties. Therefore, their syntheses, mechanisms, and applications are reviewed in this paper. First, we introduce the role of inorganic-organic photocatalysts, their advantages and disadvantages, and their design principles. Second, we present the top-down and bottom-up synthesis methods of the hybrid materials. The interaction between inorganic and organic components in hybrid materials is discussed, followed by how to improve inorganic-organic photocatalysts. Third, the applications of hybrid materials in the field of photocatalysis, such as realizing hydrogen evolution, organic pollutant degradation, heavy metals and CO 2 reduction, sterilization, and nitrogen fixation, are examined. Finally, the application prospects and development directions of inorganic-organic hybrid materials are explored and the unsolved problems are described. In this paper, the design principles and synthesis strategies of inorganic–organic hybrid materials are reviewed and their functions and mechanisms are described. Finally, the application of inorganic–organic hybrid materials in photocatalysis is introduced.

Ma X., Shi Y., Liu J., Li X., Cui X., Tan S., Zhao J., Wang B.

Breaking the strong covalent O-H bond of an isolated H2O molecule is difficult, but it can be largely facilitated when the H2O molecule is connected with others through hydrogen-bonding. How a hydrogen-bond network forms and performs becomes crucial for water splitting in natural photosynthesis and artificial photocatalysis and is awaiting a microscopic and spectroscopic understanding at the molecular level. At the prototypical photocatalytic H2O/anatase-TiO2(001)-(1×4) interface, we report the hydrogen-bond network can promote the coupled proton and hole transfer for water splitting. The formation of a hydrogen-bond network is controlled by precisely tuning the coverage of water to above one monolayer. Under ultraviolet (UV) light irradiation, the hydrogen-bond network opens a cascaded channel for the transfer of a photoexcited hole, concomitant with the release of the proton to form surface hydroxyl groups. The yielded hydroxyl groups provide excess electrons to the TiO2 surface, causing the reduction of Ti4+ to Ti3+ and leading to the emergence of gap states, as monitored by in situ UV/X-ray photoelectron spectroscopy. The density functional theory calculation reveals that the water splitting becomes an exothermic process through hole oxidation with the assistance of the hydrogen-bond network. In addition to the widely concerned exotic activity from photocatalysts, our study demonstrates the internal hydrogen-bond network, which is ubiquitous at practical aqueous/catalyst interfaces, is also indispensable for water splitting.

Chen S., Zhang Z., Jiang W., Zhang S., Zhu J., Wang L., Ou H., Zaman S., Tan L., Zhu P., Zhang E., Jiang P., Su Y., Wang D., Li Y.

The renewable energy-powered electrolytic reduction of carbon dioxide (CO2) to methane (CH4) using water as a reaction medium is one of the most promising paths to store intermittent renewable energy and address global energy and sustainability problems. However, the role of water in the electrolyte is often overlooked. In particular, the slow water dissociation kinetics limits the proton-feeding rate, which severely damages the selectivity and activity of the methanation process involving multiple electrons and protons transfer. Here, we present a novel tandem catalyst comprising Ir single-atom (Ir1)-doped hybrid Cu3N/Cu2O multisite that operates efficiently in converting CO2 to CH4. Experimental and theoretical calculation results reveal that the Ir1 facilitates water dissociation into proton and feeds to the hybrid Cu3N/Cu2O sites for the *CO protonation pathway toward *CHO. The catalyst displays a high Faradaic efficiency of 75% for CH4 with a current density of 320 mA cm-2 in the flow cell. This work provides a promising strategy for the rational design of high-efficiency multisite catalytic systems.

An B., Li Z., Wang Z., Zeng X., Han X., Cheng Y., Sheveleva A.M., Zhang Z., Tuna F., McInnes E.J., Frogley M.D., Ramirez-Cuesta A.J., S. Natrajan L., Wang C., Lin W., et. al.

Natural gas, consisting mainly of methane (CH4), has a relatively low energy density at ambient conditions (~36 kJ l−1). Partial oxidation of CH4 to methanol (CH3OH) lifts the energy density to ~17 MJ l−1 and drives the production of numerous chemicals. In nature, this is achieved by methane monooxygenase with di-iron sites, which is extremely challenging to mimic in artificial systems due to the high dissociation energy of the C–H bond in CH4 (439 kJ mol−1) and facile over-oxidation of CH3OH to CO and CO2. Here we report the direct photo-oxidation of CH4 over mono-iron hydroxyl sites immobilized within a metal–organic framework, PMOF-RuFe(OH). Under ambient and flow conditions in the presence of H2O and O2, CH4 is converted to CH3OH with 100% selectivity and a time yield of 8.81 ± 0.34 mmol gcat−1 h−1 (versus 5.05 mmol gcat−1 h−1 for methane monooxygenase). By using operando spectroscopic and modelling techniques, we find that confined mono-iron hydroxyl sites bind CH4 by forming an [Fe–OH···CH4] intermediate, thus lowering the barrier for C–H bond activation. The confinement of mono-iron hydroxyl sites in a porous matrix demonstrates a strategy for C–H bond activation in CH4 to drive the direct photosynthesis of CH3OH. The partial oxidation of CH4 to CH3OH is challenging to perform in artificial systems due to ready over-oxidation to CO and CO2. Here by confining mono-iron hydroxyl sites in a metal–organic framework, photo-oxidation of CH4 to CH3OH is achieved with high selectivity and time yield.

Zheng K., Wu Y., Zhu J., Wu M., Jiao X., Li L., Wang S., Fan M., Hu J., Yan W., Zhu J., Sun Y., Xie Y.

The huge challenge for CH4 photooxidation into CH3OH lies in the activation of the inert C-H bond and the inhibition of CH3OH overoxidation. Herein, we design two-dimensional in-plane Z-scheme heterostructures composed of two different metal oxides, with efforts to polarize the symmetrical CH4 molecules and strengthen the O-H bond in CH3OH. As a prototype, we first fabricate ZnO/Fe2O3 porous nanosheets, where high-resolution transmission electron microscopy and in situ X-ray photoelectron spectroscopy affirm their in-plane Z-scheme heterostructure. In situ Fourier transform infrared spectra and in situ electron paramagnetic resonance spectra demonstrate their higher amount of ·CH3 radicals relative to the pristine ZnO porous nanosheets, in which density functional theory calculations validate that the high local charge accumulation on Fe sites lowers the CH4 adsorption energy from 0.14 to 0.06 eV. Moreover, the charge-accumulated Fe sites strengthen the polarity of the O-H bond in CH3OH through transferring electrons to the O atoms, confirmed by the increased barrier from 0.30 to 2.63 eV for *CH3O formation, which inhibits the homolytic O-H bond cleavage and thus suppresses CH3OH overoxidation. Accordingly, the CH3OH selectivity over ZnO/Fe2O3 porous nanosheets reaches up to nearly 100% with an activity of 178.3 μmol-1 gcat-1, outperforming previously reported photocatalysts without adding any oxidants under room temperature and ambient pressure.

Wang Y., Chen E., Tang J.

Photocatalytic CO2 conversion to value-added chemicals is a promising solution to mitigate the current energy and environmental issues but is a challenging process. The main obstacles include the inertness of CO2 molecule, the sluggish multi-electron process, the unfavorable thermodynamics, and the selectivity control to preferable products. Furthermore, the lack of fundamental understanding of the reaction pathways accounts for the very moderate performance in the field. Therefore, in this Perspective, we attempt to discuss the possible reaction mechanisms toward all C1 and C2 value-added products, taking into account the experimental evidence and theoretical calculation on the surface adsorption, proton and electron transfer, and products desorption. Finally, the remaining challenges in the field, including mechanistic understanding, reactor design, economic consideration, and potential solutions, are critically discussed by us.

Bie C., Wang L., Yu J.

Summary The hydrogen economy is a sunrise industry, which is considered the ultimate solution to power the future society. Photocatalytic overall water splitting is projected as a potential technology for H2 production. However, its performance is still far from meeting the criteria for large-scale production. This paper argues that photocatalytic overall water splitting is theoretically and practically hard to achieve. The limiting factors, including unfavorable thermodynamics, slow kinetics, dissolved oxygen, and rapid backward reaction, are discussed. This paper is expected to give readers a better understanding of the photocatalytic overall water splitting and analyze the associated challenges in every subtle aspect.

Cheng H., Cheng J., Wang L., Xu H.

Tao X., Zhao Y., Wang S., Li C., Li R.

The conversion and storage of solar energy to chemical energy via artificial photosynthesis holds significant potential for optimizing the energy situation and mitigating the global warming effect. Photocatalytic water splitting utilizing particulate semiconductors offers great potential for the production of renewable hydrogen, while this cross-road among biology, chemistry, and physics features a topic with fascinating interdisciplinary challenges. Progress in photocatalytic water splitting has been achieved in recent years, ranging from fundamental scientific research to pioneering scalable practical applications. In this review, we focus mainly on the recent advancements in terms of the development of new light-absorption materials, insights and strategies for photogenerated charge separation, and studies towards surface catalytic reactions and mechanisms. In particular, we emphasize several efficient charge separation strategies such as surface-phase junction, spatial charge separation between facets, and polarity-induced charge separation, and also discuss their unique properties including ferroelectric and photo-Dember effects on spatial charge separation. By integrating time- and space-resolved characterization techniques, critical issues in photocatalytic water splitting including photoinduced charge generation, separation and transfer, and catalytic reactions are analyzed and reviewed. In addition, photocatalysts with state-of-art efficiencies in the laboratory stage and pioneering scalable solar water splitting systems for hydrogen production using particulate photocatalysts are presented. Finally, some perspectives and outlooks on the future development of photocatalytic water splitting using particulate photocatalysts are proposed.

Collado L., Reñones P., Fermoso J., Fresno F., Garrido L., Pérez-Dieste V., Escudero C., Hernández-Alonso M.D., Coronado J.M., Serrano D.P., de la Peña O’Shea V.A.

The development of sustainable processes for CO 2 reduction to fuels and chemicals is one of the most important challenges to provide clean energy solutions. The use of sunlight as renewable energy source is an interesting alternative to power the electron transfer required for artificial photosynthesis. Even if redox sites are mainly responsible for this process, other reactive acidic/basic centers also contribute to the overall reaction pathway. However, a full understanding of the CO 2 photoreduction mechanism is still a scientific challenge. In fact, the lack of agreement on standardized comparison criteria leads to a wide distribution of reported productions, even using the same catalyst, which hinders a reliable interpretation. An additional difficulty is ascertaining the origin of carbon-containing products and effect of surface carbon residues, as well as the reaction intermediates and products under real dynamic conditions. To determine the elusive reaction mechanism, we report an interconnected strategy combining in-situ spectroscopies, theoretical studies and catalytic experiments. These studies show that CO 2 photoreduction productions are influenced by the presence of carbon deposits (i.e. organic molecules, carbonates and bicarbonates) over the TiO 2 surface. Most importantly, the acid/base character of the surface and the reaction medium play a key role in the selectivity and deactivation pathways. This TiO 2 deactivation is mainly initiated by the formation of carbonates and peroxo- species, while activity can be partially recovered by a mild acid washing treatment. We anticipate that these findings and methodology enlighten the main shadows still covering the CO 2 reduction mechanism, and, most importantly, provide essential clues for the design of emergent materials and reactions for photo(electro)catalytic energy conversion. • Both redox sites and acidic/basic centers contribute to the CO 2 reduction pathway. • UV irradiation increases the surface pH, influencing selectivity and stability. • Carbonates and peroxo-species initiate TiO 2 deactivation. • In-situ NAP-XPS, DRIFTS, Raman and 13 C NMR provides evidence of reaction mechanism.

Cheng S., Sun Z., Lim K.H., Gani T.Z., Zhang T., Wang Y., Yin H., Liu K., Guo H., Du T., Liu L., Li G.K., Yin Z., Kawi S.

The solar-energy-driven photoreduction of CO2 has recently emerged as a promising approach to directly transform CO2 into valuable energy sources under mild conditions. As a clean-burning fuel and drop-in replacement for natural gas, CH4 is an ideal product of CO2 photoreduction, but the development of highly active and selective semiconductor-based photocatalysts for this important transformation remains challenging. Hence, significant efforts have been made in the search for active, selective, stable, and sustainable photocatalysts. In this review, recent applications of cutting-edge experimental and computational materials design strategies toward the discovery of novel catalysts for CO2 photocatalytic conversion to CH4 are systematically summarized. First, insights into effective experimental catalyst engineering strategies, including heterojunctions, defect engineering, cocatalysts, surface modification, facet engineering, and single atoms, are presented. Then, data-driven photocatalyst design spanning density functional theory (DFT) simulations, high-throughput computational screening, and machine learning (ML) is presented through a step-by-step introduction. The combination of DFT, ML, and experiments is emphasized as a powerful solution for accelerating the discovery of novel catalysts for photocatalytic reduction of CO2. Last, challenges and perspectives concerning the interplay between experiments and data-driven rational design strategies for the industrialization of large-scale CO2 photoreduction technologies are described.

Ma M., Zhang S., Jia M., Li T., Chen J., Zhao S., Ge S., Zheng Z., Wu S., Fa W.

Ma M., Fang Y., Huang Z., Wu S., He W., Ge S., Zheng Z., Zhou Y., Fa W., Wang X.

AbstractPhoto‐/electro‐catalytic CO2 reduction with H2O to produce fuels and chemicals offers a dual solution to address both environmental and energy challenges. For a long time, catalyst design in this reaction system has primarily focused on optimizing reduction sites to improve the efficiency or guide the reaction pathway of the CO2 reduction half‐reaction. However, less attention has been paid to designing activation sites for H2O to modulate the H2O dissociation half‐reaction. Impressively, the rate‐determining step in overall CO2 reduction is the latter, and it influences the evolution direction and formation energy of carbon‐containing intermediates through the proton‐coupled electron transfer process. Herein, we summarize the mechanism of the H2O dissociation half‐reaction in modulating CO2 reduction performance based on cutting‐edge research. These analyses aim to uncover the potential regulatory mechanisms by which H2O activation influences CO2 reduction pathways and conversion efficiency, and to establish a mechanism‐structure‐performance relationship that can guide the design and development of high‐efficiency catalytic materials. A summary of advanced characterization techniques for investigating the dissociation mechanism of H2O is presented. We also discuss the challenges and offer perspectives on the future design of activation sites to improve the performance of photo‐/electro‐catalytic CO2 reduction.

Ma M., Fang Y., Huang Z., Wu S., He W., Ge S., Zheng Z., Zhou Y., Fa W., Wang X.

AbstractPhoto‐/electro‐catalytic CO2 reduction with H2O to produce fuels and chemicals offers a dual solution to address both environmental and energy challenges. For a long time, catalyst design in this reaction system has primarily focused on optimizing reduction sites to improve the efficiency or guide the reaction pathway of the CO2 reduction half‐reaction. However, less attention has been paid to designing activation sites for H2O to modulate the H2O dissociation half‐reaction. Impressively, the rate‐determining step in overall CO2 reduction is the latter, and it influences the evolution direction and formation energy of carbon‐containing intermediates through the proton‐coupled electron transfer process. Herein, we summarize the mechanism of the H2O dissociation half‐reaction in modulating CO2 reduction performance based on cutting‐edge research. These analyses aim to uncover the potential regulatory mechanisms by which H2O activation influences CO2 reduction pathways and conversion efficiency, and to establish a mechanism‐structure‐performance relationship that can guide the design and development of high‐efficiency catalytic materials. A summary of advanced characterization techniques for investigating the dissociation mechanism of H2O is presented. We also discuss the challenges and offer perspectives on the future design of activation sites to improve the performance of photo‐/electro‐catalytic CO2 reduction.

Chang P., Yu H., Zhang Y., Gao Y., Zheng L., Li K., Du Y., Wu L., Liu J.

Li Z., Hu Y., Lan H., Xia H.

Metal–air batteries are highly valued for their exceptional energy efficiency and affordability. Identifying suitable electrode materials is crucial to fully harness their potential. Carbon nanomaterials, renowned for their excellent conductivity, vast specific surface area, robust stability, and minimal volume expansion, have emerged as a preferred choice for many. However, early characterization techniques struggle to precisely pinpoint catalytic active sites across various electrocatalytic reactions, making it challenging to comprehend the experimental impact of different active site types on these reactions. This has posed a significant obstacle to unveiling the catalytic mechanism and developing efficient catalysts. With advancements in characterization methods, studies on carbon nanomaterials have progressed rapidly. Herein, the structure of carbon nanomaterial catalysts are reshaped by the researchers to improve catalytic efficiency, resulting in four distinct structural forms: metal‐free carbon–based materials, atomically dispersed metal carbon‐based materials, metal nanoparticles encapsulated in carbon‐based materials, and metal nanoparticles supported on carbon‐based materials. In this review, the features of these structural forms and their application contexts, detailing the synthesis methods and catalytic effects of each form, are highlighted. This article concludes with an overview of recent advancements and future directions in the characterization techniques of carbon materials.

Xiong Q., Yu L., An N., Cong H., Zhao W.

Conversion of greenhouse gas carbon dioxide to valuable products is important to reach carbon balance and sustainability, of which catalytic cycloaddition of CO2 to cyclic carbonates has attracted much attention. Here, a biomass-derived zwitterionic polymer has been synthesized and characterized. The prepared polymer with porous structure was employed for the catalytic cycloaddition of atmospheric CO2 and epoxides in excellent yields with a broad substrate scope under solvent-, co-catalyst, and metal-free conditions. The synthesized polymer with good thermostability could be readily recovered and recycled four times at least. Moreover, this catalytic system provided satisfactory performance with up to 96% yield of cyclic carbonate even in the gram-level scale-up reaction under the optimal standard conditions. The catalytic mechanism has also been preliminarily discussed.

Tian F., Li W., Chen R., Yang J., Li Q., Ran W., Li N., Du D., Yan T.

Peng R., Ren Y., Si Y., Huang K., Zhou J., Duan L., Li N.

Wu J., Yang T., Song Y., Zhao N., Xiaodong T., Liu Z.

Zhao L., Hou H., Wang S., Wang L., Yang Y., Bowen C.R., Wang J., Liao Z., Yang D., Yan R., Yang W.

AbstractDespite the development of a range of photocatalysts for CO2 reduction, the practical applications are significantly limited by low conversion efficiencies and their reliance on sacrificial agents, which are rooted in thermodynamic and kinetic challenges related to CO2 conversion. Here, the engineering of Co single atoms in ultrathin single‐crystal BiOCl nanosheets for boosted photocatalytic CO2 reduction is reported. The engineering of Co atoms modulates the distribution of photogenerated charges at the catalyst surface, controlling key surface reaction dynamics and suppressing surface electron‐hole recombination. This modulation also improves light absorption and enhances CO2 adsorption and activation, leading to more efficient surface reactions. Notably, CO2 is stably adsorbed onto the (001) face of BiOCl through a Bi‐O‐C(= O)‐Co‐O coordination unit, which lowers the activation energy for CO2 reduction and reduces the formation energy of COOH− intermediates. As a result, the BiOCl photocatalysts achieve a CO formation rate of 183.9 µmol g−1 h−1, when irradiated with a 300 W Xe lamp without cocatalysts or sacrificial agents. It represents an ≈13‐fold increase compared to that of pristine BiOCl, and surpasses most reported Bi‐based photocatalysts to date. Current work provides valuable insights into engineering of single atoms for developing advanced CO2‐reduction photocatalysts.

Wang M., Zhang G., Wang H., Wang Z., Zhou Y., Nie X., Yin B.H., Song C., Guo X.

Fu C., Wan Z., Yang X., Zhang J., Zhang Z.

We summarized the design strategies for photocatalysts to enhance CO2 reduction and accepted pathways for selective photocatalytic CO2 conversion.

Deng S., Wang N., Zhu Y., Thummavichai K.

Nowadays, the excessive use of fossil fuels has led to a global energy shortage and exacerbated the greenhouse effect.

Guan Q., Ran W., Zhang D., Li W., Li N., Huang B., Yan T.

AbstractPhotocatalytic CO2 reduction is considered as a promising strategy for CO2 utilization and producing renewable energy, however, it remains challenge in the improvement of photocatalytic performance for wide‐band‐gap photocatalyst with controllable product selectivity. Herein, the sulfur‐doped In(OH)3 (In(OH)xSy‐z) nanocubes are developed for selective photocatalytic reduction of CO2 to CH4 under simulated light irradiation. The CH4 yield of the optimal In(OH)xSy‐1.0 can be enhanced up to 39 times and the CH4 selectivity can be regulated as high as 80.75% compared to that of pristine In(OH)3. The substitution of sulfur atoms for hydroxyl groups in In(OH)3 enhances the visible light absorption capability, and further improves the hydrophilicity behavior, which promotes the H2O dissociation into protons (H*) and accelerates the dynamic proton‐feeding CO2 hydrogenation. In situ DRIFTs and DFT calculation confirm that the non‐metal sulfur sites significantly weaken the over‐potential of the H2O oxidation and prevent the formation of ·OH radicals, enabling the stabilization of *CHO intermediates and thus facilitating CH4 production. This work highlights the promotion effect of the non‐metal doping engineering on wide‐band‐gap photocatalysts for tailoring the product selectivity in photocatalytic CO2 reduction.

Cui Y., Labidi A., Liang X., Huang X., Wang J., Li X., Dong Q., Zhang X., Othman S.I., Allam A.A., Bahnemann D.W., Wang C.

AbstractOver the past decades, CO2 greenhouse emission has been considerably increased, causing global warming and climate change. Indeed, converting CO2 into valuable chemicals and fuels is a desired option to resolve issues caused by its continuous emission into the atmosphere. Nevertheless, CO2 conversion has been hampered by the ultrahigh dissociation energy of C=O bonds, which makes it thermodynamically and kinetically challenging. From this prospect, photocatalytic approaches appear promising for CO2 reduction in terms of their efficiency compared to other traditional technologies. Thus, many efforts have been made in the designing of photocatalysts with asymmetric sites and oxygen vacancies, which can break the charge distribution balance of CO2 molecule, reduce hydrogenation energy barrier and accelerate CO2 conversion into chemicals and fuels. Here, we review the recent advances in CO2 hydrogenation to C1 and C2 products utilizing photocatalysis processes. We also pin down the key factors or parameters influencing the generation of C2 products during CO2 hydrogenation. In addition, the current status of CO2 reduction is summarized, projecting the future direction for CO2 conversion by photocatalysis processes.