CO2 hydrogenation to hydrocarbons over heterogeneous catalysts.

Efficient electroreduction of CO 2 to multi-carbon products is a challenging reaction because of the high energy barriers for CO 2 activation and CC coupling, which can be tuned by designing the metal centers and coordination environments of catalysts. Here, we design single atom copper encapsulated on N-doped porous carbon (Cu-SA/NPC) catalysts for reducing CO 2 to multi-carbon products. Acetone is identified as the major product with a Faradaic efficiency of 36.7% and a production rate of 336.1 μg h −1. Density functional theory (DFT) calculations reveal that the coordination of Cu with four pyrrole-N atoms is the main active site and reduces the reaction free energies required for CO 2 activation and CC coupling. The energetically favorable pathways for CH 3 COCH 3 production from CO 2 reduction are proposed and the origin of selective acetone formation on Cu-SA/NPC is clarified. This work provides insight into the rational design of efficient electrocatalysts for reducing CO 2 to multi-carbon products.

Density functional theory (DFT) calculations on Pd-Cu bimetallic catalysts reveal that the stepped PdCu(111) surface with coordinatively unsaturated Pd atoms exposed on the top is superior for CO 2 and H 2 activation and for CO 2 hydrogenation to methanol in comparison to the flat Cu-rich PdCu 3 (111) surface. The energetically preferred path for CO 2 to CH 3 OH over PdCu(111) proceeds through CO 2 * → HCOO* → HCOOH* → H 2 COOH* → CH 2 O* → CH 3 O* → CH 3 OH*. CO formation from CO 2 via a reverse water-gas shift (RWGS) proceeds more quickly than CH 3 OH formation in terms of kinetic calculations, in line with experimental observation. A small amount of water, which is produced in situ from both RWGS and CH 3 OH formation, can accelerate CO 2 conversion to methanol by reducing the kinetic barriers for O−H bond formation steps and enhancing the TOF. Water participation in the reaction alters the rate-limiting step according to the degree of rate control (DRC) analysis. In comparison to CO 2 , CO hydrogenation to methanol on PdCu(111) encounters higher barriers and thus is slower in kinetics. Complementary to the DFT results, CO 2 hydrogenation experiments over SiO 2 -supported bimetallic catalysts show that the Pd-Cu(0.50) that is rich in a PdCu alloy phase is more selective to methanol than the PdCu 3 -rich Pd-Cu(0.25). Moreover, advanced CH 3 OH selectivity is also evidenced on Pd-Cu(0.50) at a specific water vapor concentration (0.03 mol %), whereas that of Pd-Cu(0.25) is not comparable. The present work clearly shows that the PdCu alloy surface structure has a major effect on the reaction pathway, and the presence of water can substantially influence the kinetics in CO 2 hydrogenation to methanol.

Photoreduction of CO 2 to C 2 + solar fuel is a promising carbon-neutral technology for renewable energy. This strategy is challenged by its low productivity due to low efficiency in multielectron utilization and slow CÀ C coupling kinetics. This work reports a dualmetal photocatalyst consisting of atomically dispersed indium and copper anchored on polymeric carbon nitride (InCu/PCN), on which the photoreduction of CO 2 delivered an excellent ethanol production rate of 28.5 μmol g À 1 h À 1 with a high selectivity of 92 %. Coupled experimental investigation and DFT calculations reveal the following mechanisms underpinning the high performance of this catalyst. Essentially, the InÀ Cu interaction enhances the charge separation by accelerating charge transfer from PCN to the metal sites. Indium also transfers electrons to neighboring copper via CuÀ NÀ In bridges, increasing the electron density of copper active sites. Furthermore, InÀ Cu dual-metal sites promote the adsorption of *CO intermediates and lower the energy barrier of CÀ C coupling.

Density functional theory (DFT) calculations were carried out to investigate the mechanism of CO2 hydrogenation in production of C1 and C2 hydrocarbons over Cu–Fe bimetallic catalyst. CH* is found to be the most favorable monomeric species for production of CH4 and C2H4 via C–C coupling of two CH* species and subsequent hydrogenation. On the bimetallic Cu–Fe(100) surface at 4/9 ML Cu coverage, the energetically preferred path for CH* formation goes through CO2* → HCOO* → HCOOH* → HCO* → HCOH* → CH*, in which both the HCOO* → HCOOH* and HCO* → HCOH* steps have substantial barriers. The bimetallic surface suppresses CH4 formation and is more selective to C2H4 due to the higher hydrogenation barrier of CH2* species relative to those for C–C coupling and CH–CH* conversion to C2H4. On monometallic Fe(100) surface, CH* formation goes through a path of CO2* → CO* → HCO* → HCOH* → CH*, different from that identified on Cu–Fe(100). The hydrogenation of HCO* to HCOH* is the rate-limiting step that controls CO2 conversion to CH4 and C2H4. CH4 formation is kinetically more favored, with a 0.3 eV lower energy barrier, than C2H4 formation. The bimetallic combination of Cu and Fe enhances CO2 conversion by reducing the kinetic barriers, and alters the selectivity preference to more valuable C2H4 from CH4 on monometallic Fe surface. C2H6 can be produced from further hydrogenation of C2H4 with moderate barriers.

to improve therapeutic effects and reduce recurrence of tumors. [3][4][5] Although there have been methodological advances, therapeutic schemes devised to challenge cancers are frequently thwarted due to the lack of correlation between the pharmacokinetics (PK) and pharmacodynamics (PD) of chemodrugs and transplanted immune cells in vivo, which results in inadequate drug/cell dosages and intervals and compromised therapeutic effects. Therefore, a visible method to objectively evaluate and therefore precisely tailor the behaviors of chemodrugs and transplanted cells in vivo to obtain synergistic therapeutic effects would be of great importance.Recently, various imaging techniques including computed tomography (CT), magnetic resonance imaging (MRI), as well as positron emission tomography (PET) and single photon emission computed tomography (SPECT) have been employed for in vivo imaging. However, it is hard to realize in situ, real-time imaging of multiple events in living bodies simultaneously due to insufficient spatial resolution, temporal resolution, as well as the safety risk. Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) is an emerging technology which offers deeper tissue penetration, higher spatial resolution, and higher temporal resolution compared with the traditional fluorescence imaging (400-900 nm), due to the reduced photon absorption and scattering as well as negligible tissue autofluorescence. In addition, fluorescence imaging provides multiplexed-channel images for its high spectral resolution. Herein, we demonstrated a novel concept of multiplexed NIR-II fluorescence imaging strategy to program the combinational therapy of tumor, in which the profiles of both chemodrugs and immune cells were simultaneously monitored by taking the advantages of NIR-II imaging technology, and therefore the administration of chemotherapy and immunotherapy could be rationally optimized to obtain the optimal therapeutic efficacy.As a proof of concept depicted in Scheme 1, a two-channel NIR-II imaging method was developed to demonstrate how the chemotherapy and immunotherapy were programed to Combined chemotherapy and immunotherapy have demonstrated great potential in cancer treatment. However, it is difficult to provide clear information of the pharmacokinetics and pharmacodynamics of chemodrugs and transplanted immune cells in vivo by traditional approaches, resulting in inadequate therapy. Here, a multiplexed intravital imaging strategy by using fluorescence in the second near-infrared window (NIR-II) is first developed to visualize the two events of chemotherapy and immunotherapy in vivo, so that a combinational administration is programed to improve the therapeutical effects against a mouse model of human breast cancer. In detail, Ag 2 Se quantum dots (QDs) (λ Em = 1350 nm) loaded with stromal-cell-derived factor-1α (SDF-1α) and chemodrug doxorubicin (DOX) are first administrated to deliver the SDF-1α and DOX to the tumor site. After their arrival, monitored by Ag 2 Se QD fluoresce...

climate change. [2] Many countries established legislations to limit the CO 2 emissions, targeting at carbon neutrality. [3] Meanwhile, efficient and clean battery systems are being developed. The lithium-ion battery (LIB) is the most successful and widely used system. [4] However, the relatively low energy density severely hindered the applications of LIBs. Recently, metalair batteries have attracted much attention due to their ultrahigh energy density. [5] However, most of them need to work in a pure oxygen environment. [6] Therefore, an energy-storage system directly utilizing CO 2 gas as redox medium is highly favorable.In 2013, Archer and co-workers proposed the concept of Li-CO 2 battery for CO 2 capture and energy storage, in which Li metal and CO 2 gas are the active materials in the anode and cathode side, respectively. [7] During discharge, Li + reacts with CO 2 to generate Li 2 CO 3 and carbon as discharge products, which is a CO 2 reduction reaction (CO 2 RR) process described as 4Li + + 3CO 2 + 4e − → 2Li 2 CO 3 + C. [8] In the reverse charging process, a CO 2 evolution reaction (CO 2 ER) occurs by decomposing Li 2 CO 3 into Li + and CO 2 gas. Many merits are identified for the Li-CO 2 battery system like the direct employing greenhouse gas of CO 2 and the high theoretical energy density of 1876 Wh kg −1 . [9] However, issues including but not limited to the large overpotential, poor cycling performance, and inferior rate capability significantly hinder the application of Li-CO 2 batteries. One dominating reason for these issues is the intrinsically sluggish kinetics of the CO 2 RR and CO 2 ER processes.Therefore, the key task for the practical application of Li-CO 2 batteries is to develop highly efficient catalysts toward the CO 2 RR and CO 2 ER. Large varieties of catalysts, such as carbon-based catalysts, [6,8a,b,10] single-metal-atom catalysts, [11] adjacent metal atoms catalyst, [12] nanostructured metal/alloy catalysts, [13] and transition metal compound catalysts [14] were developed for Li-CO 2 batteries to facilitate the CO 2 reduction and promote the decomposition of Li 2 CO 3 . Metallic ruthenium (Ru) and Ru-based materials is an important catalyst family for the CO 2 RR and CO 2 ER. [15] Ru catalyst has intrinsic advantage in The Li-CO 2 battery is a novel strategy for CO 2 capture and energy-storage applications. However, the sluggish CO 2 reduction and evolution reactions cause large overpotential and poor cycling performance. Herein, a new catalyst containing well-defined ruthenium (Ru) atomic clusters (Ru AC ) and single-atom Ru-N 4 (Ru SA ) composite sites on carbon nanobox substrate (Ru AC+SA @NCB) (NCB = nitrogen-doped carbon nanobox) is fabricated by utilizing the different complexation effects between the Ru cation and the amine group (NH 2 ) on carbon quantum dots or nitrogen moieties on NCB. Systematic experimental and theoretical investigations demonstrate the vital role of electronic synergy between Ru AC and Ru-N 4 in improving the electrocatalytic activity toward the C...

Facilitating the cleavage of a NN bond and suppressing the competition hydrogen evolution reaction is essential, and but still remains a challenge in nitrogen reduction reaction (NRR). Crystal phase tailoring is an effective approach to optimize the energy barrier during the NRR process to improve the catalytic efficiency. Herein, a boron-doping strategy to induce phase transfer from hexagonal Mo 2 C to cubic Mo 2 C for regulating the electronic structure and catalytic properties of electrocatalysts toward NRR is reported. The B doped cubic Mo 2 C is found to increase the exposure of active sites, regulate the d band center of Mo for enhancing the adsorption and activation of nitrogen, and reduce the energy barrier of NRR pathway, giving rise to a high ammonia yield of 52.1 μg h −1 mg −1 at −0.6 V versus reversible hydrogen electrode under ambient conditions. More importantly, the hydrogen adsorption on the surface of electrocatalyst is significantly inhibited due to the B-doping, further improving the faradic efficiency to 36.9%, which is 4 times that of hexagonal Mo 2 C (9%). This work not only sheds light on the atomic-scale design of efficient NRR electrocatalysts, but also provides a promising avenue for synchronizing the catalytic activity and selectivity for catalytic reactions.