Highly Selective CO2 Electroreduction to Multi-carbon Alcohols via Amine Modified Copper Nanoparticles at Acidic Conditions.

Electroreduction of CO2 into multi-carbon (C2+) products (e.g. C2+ alcohols) offers a promising way for CO2 utilization. Use of strong alkaline electrolytes is favorable to producing C2+ products. However, CO2 can react with hydroxide to form carbonate/bicarbonate, which results in low carbon utilization efficiency and poor stability. Using acidic electrolyte is an efficient way to solve the problems, but it is a challenge to achieve high selectivity of C2+ products. Here we report that the amine modified copper nanoparticles exhibit high selectivity of C2+ products and carbon utilization at acidic condition. The Faradaic efficiency (FE) of C2+ products reach up to 81.8% at acidic media (pH=2) with a total current density of 410 mA cm-2 over n-butylamine modified Cu. Especially the FE of C2+ alcohols is 52.6%, which is higher than those reported for CO2 electroreduction at acidic condition. In addition, the single-pass carbon efficiency towards C2+ production reach up to 60%. Detailed studies demonstrate that the amine molecule on the surface of Cu cannot only enhance the formation, adsorption and coverage of *CO, but also provide a hydrophobic environment, which result in the high selectivity of C2+ alcohols at acidic condition.

Synergy of Cu/C3 N4 Interface and Cu Nanoparticles Dual Catalytic Regions in Electrolysis of CO to Acetic Acid.

Electrochemical reduction reaction of carbon monoxide (CORR) offers a promising way to manufacture acetic acid directly from gaseous CO and water at mild condition. Herein, we discovered that the graphitic carbon nitride (g-C3 N4 ) supported Cu nanoparticles (Cu-CN) with the appropriate size showed a high acetate faradaic efficiency of 62.8 % with a partial current density of 188 mA cm-2 in CORR. In situ experimental and density functional theory calculation studies revealed that the Cu/C3 N4 interface and metallic Cu surface synergistically promoted CORR into acetic acid. The generation of pivotal intermediate -*CHO is advantage around the Cu/C3 N4 interface and migrated *CHO facilitates acetic acid generation on metallic Cu surface with promoted *CHO coverage. Moreover, continuous production of acetic acid aqueous solution was achieved in a porous solid electrolyte reactor, indicating the great potential of Cu-CN catalyst in the industrial application.

Mechanism by Which Cholesterol Induces Sphingomyelin Conformational Changes at an Air/Water Interface.

This work investigates the interactions in cholesterol and sphingomyelin monolayers at the molecular level by high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The SFG spectra of natural egg sphingomyelin (ESM) as a function of cholesterol concentration are obtained at an air/water interface under different polarization combinations. The analysis of the spectra shows that cholesterol can induce sphingomyelin conformational changes at an air/water interface. The mechanism is proposed. When cholesterol is inserted into the ESM monolayer, the inherent intramolecular hydrogen bonds between the phosphate moiety and 3OH in the sphingosine backbones are destroyed. During this process, the sphingosine backbones become more ordered, while the conformation of the N-linked long acid chain remains unaltered. The OH of the cholesterol head group can bind to the -PO-2 of the ESM molecule, and the orientation of the -PO-2 in the head groups changes to be more parallel to the interface.

Efficient electroreduction of CO2 to C2+ products on CeO2 modified CuO.

Electrocatalytic reduction of CO2 into multicarbon (C2+) products powered by renewable electricity offers one promising method for CO2 utilization and promotes the storage of renewable energy under an ambient environment. However, there is still a dilemma in the manufacture of valuable C2+ products between balancing selectivity and activity. In this work, cerium oxides were combined with CuO (CeO2/CuO) and showed an outstanding catalytic performance for C2+ products. The faradaic efficiency of the C2+ products could reach 75.2% with a current density of 1.21 A cm-2. In situ experiments and density functional theory (DFT) calculations demonstrated that the interface between CeO2 and Cu and the subsurface Cu2O coexisted in CeO2/CuO during CO2RR and two competing pathways for C-C coupling were promoted separately, of which hydrogenation of *CO to *CHO is energetically favoured. In addition, the introduction of CeO2 also enhanced water activation, which could accelerate the formation rate of *CHO. Thus, the selectivity and activity for C2+ products over CeO2/CuO can be improved simultaneously.

The in situ study of surface species and structures of oxide-derived copper catalysts for electrochemical CO2 reduction.

Oxide-derived copper (OD-Cu) has been discovered to be an effective catalyst for the electroreduction of CO2 to C2+ products. The structure of OD-Cu and its surface species during the reaction process are interesting topics, which have not yet been clearly discussed. Herein, in situ surface-enhanced Raman spectroscopy (SERS), operando X-ray absorption spectroscopy (XAS), and 18O isotope labeling experiments were employed to investigate the surface species and structures of OD-Cu catalysts during CO2 electroreduction. It was found that the OD-Cu catalysts were reduced to metallic Cu(0) in the reaction. CuO x species existed on the catalyst surfaces during the CO2RR, which resulted from the adsorption of preliminary intermediates (such as *CO2 and *OCO-) on Cu instead of on the active sites of the catalyst. It was also found that abundant interfaces can be produced on OD-Cu, which can provide heterogeneous CO adsorption sites (strong binding sites and weak binding sites), leading to outstanding performance for obtaining C2+ products. The Faradaic efficiency (FE) for C2+ products reached as high as 83.8% with a current density of 341.5 mA cm-2 at -0.9 V vs. RHE.

Visible- and NIR-Light Responsive Black-Phosphorus-Based Nanostructures in Solar Fuel Production and Environmental Remediation.

Direct utilization of the full spectrum of renewable solar light, in particular the visible- and near-infrared (NIR) portions, is currently receiving a great deal of attention in solar-to-chemical energy conversion-a clean, economically, and environmentally sustainable process. Black phosphorus (BP), a newly emerging class of ultrathin 2D nanomaterials rediscovered in early 2014, fulfills this purpose due to its unique properties like high charge-carrier mobility and tunable direct-bandgap. To this end, the rational combinations of BP in the form of few-layer nanosheets or ultrasmall quantum dots with a range of organic and inorganic nanomaterials offer more versatile and robust hybrids and nanocomposites that are functional in solar fuel production and environmental remediation. Herein, the most recent and key achievements of BP-based nanostructured photocatalysts in water splitting, organic pollutant degradation, and nitrogen fixation under either visible- or NIR-light illumination are summarized. Furthermore, perspectives on the potential future research directions are provided.

Effect of Ca2+ to Sphingomyelin Investigated by Sum Frequency Generation Vibrational Spectroscopy.

The interactions between Ca2+ ions and sphingomyelin play crucial roles in a wide range of cellular activities. However, little is known about the molecular details of the interactions at interfaces. In this work, we investigated the interactions between Ca2+ ions and egg sphingomyelin (ESM) Langmuir monolayers at the air/water interface by subwavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS). We show that Ca2+ ions can induce ordering of the acyl chains in the ESM monolayer. An analysis of the one alkyl-chain-deuterated ESM revealed that the Ca2+ ions do not affect the N-linked saturated fatty acid chain, although they make the sphingosine backbone become ordered. Further analysis of the SFG-VS spectra shows that the interactions between ESM and Ca2+ ions make the orientation of the methyl group at the end of sphingosine backbone change from pointing downward to pointing upward. Moreover, a large blue shift of the phosphate group at the CaCl2 solution interface indicates, to our knowledge, new cation binding modes. Such binding causes the phosphate moiety to dehydrate, resulting in the conformation change of the phosphate moiety. Based on these results, we propose the molecular mechanism that Ca2+ ions can bind to the phosphate group and subsequently destroy the intramolecular hydrogen bond between the 3-hydroxyl group and the phosphate oxygen, which results in an ordering change of the sphingosine backbone. These findings illustrate the potential application of HR-BB-SFG-VS to investigate lipid-cation interactions and the calcium channel modulated by lipid domain formation through slight structural changes in the membrane lipid. It will also shed light on the interactions of complex molecules at surfaces and interfaces.

Spectral assignment and orientational analysis in a vibrational sum frequency generation study of DPPC monolayers at the air/water interface.

The interfacial behavior of the benchmark zwitterionic phospholipid molecule dipalmitoylphosphatidylcholine (DPPC) has been extensively investigated by surface-selective vibrational sum frequency generation spectroscopy (VSFG). However, there is still a lack of agreement between various orientational measurements of phospholipid monolayers at the air/water interface, mainly because of the difficulty in assigning congested VSFG features. In this study, polarization-dependent VSFG measurements reveal a frequency shift between the in-plane and out-of-plane antisymmetric stretching modes of the terminal methyl groups in the DPPC alkyl tails, favoring the model of Cs local symmetry rather than the previously assumed C3v symmetry. Further VSFG experiments of isotopically labeled DPPC successfully capture the vibrational signatures of the glycerol backbone. With the newly derived VSFG polarization selection rules for Cs symmetry and the refreshed spectral assignments, the average tilt angles of the alkyl tail groups, choline headgroup, and glycerol backbone of DPPC molecules can all be determined, showing the powerful capability of VSFG spectroscopy in revealing the structural details at interfaces. The VSFG polarization dependence rules and the orientational analysis procedures developed for Cs symmetry in this work are applicable to other bulky molecules in which the methyl group cannot freely rotate, and they therefore have general applications in future VSFG studies.