Electrocatalytic CO2 Upgrading to Triethanolamine by Bromine-Assisted C2 H4 Oxidation.

The electrocatalytic carbon dioxide (CO2 ) reduction is a promising approach for converting this greenhouse gas into value-added chemicals, while the capability of producing products with longer carbon chains (Cn >3) is limited. Herein, we demonstrate the Br-assisted electrocatalytic oxidation of ethylene (C2 H4 ), a major CO2 electroreduction product, into 2-bromoethanol by electro-generated bromine on metal phthalocyanine catalysts. Due to the preferential formation of Br2 over *O or Cl2 to activate the C=C bond, a high partial current density of producing 2-bromoethanol (46.6 mA⋅cm-2 ) was obtained with 87.2 % Faradaic efficiency. Further coupling with the electrocatalytic nitrite reduction to ammonia at the cathode allowed the production of triethanolamine with six carbon atoms. Moreover, by coupling a CO2 electrolysis cell for in situ C2 H4 generation and a C2 H4 oxidation/nitrite reduction cell, the capability of upgrading of CO2 and nitrite into triethanolamine was demonstrated.

Unraveling and tuning the linear correlation between CH4 and C2 production rates in CO2 electroreduction.

Although many catalysts have been reported for the CO2 electroreduction to C1 or C2 chemicals, the insufficient understanding of fundamental correlations among different products still hinders the development of universal catalyst design strategies. Herein, we first discover that the surface *CO coverage is stable over a wide potential range and reveal a linear correlation between the partial current densities of CH4 and C2 products in this potential range, also supported by the theoretical kinetic analysis. Based on the mechanism that *CHO is the common intermediate in the formation of both CH4 (*CHO â†’ CH4) and C2 (*CHO + *CO â†’ C2), we then unravel that this linear correlation is universal and the slope can be varied by tuning the surface *H or *CO coverage to promote the selectivity of CH4 or C2 products, respectively. As proofs-of-concept, using carbon-coated Cu particles, the surface *H coverage can be increased to enhance CH4 production, presenting a high CO2-to-CH4 Faradaic efficiency ( [Formula: see text] ∼52%) and an outstanding CH4 partial current density of -337 mA cm-2. On the other hand, using an Ag-doped Cu catalyst, the CO2RR selectivity is switched to the C2 pathway, with a substantially promoted [Formula: see text] of 79% and a high partial current density of -421 mA cm-2. Our discovery of tuning intermediate coverages suggests a powerful catalyst design strategy for different CO2 electroreduction pathways.

Photocatalytic CO2 conversion: from C1 products to multi-carbon oxygenates.

Photocatalytic CO2 conversion into high-value chemicals has been emerging as an attractive research direction in achieving carbon resource sustainability. The chemical products can be categorized into C1 and multi-carbon (C2+) products. In this review, we describe the recent research progress in photocatalytic CO2 conversion systems from C1 products to multi-carbon oxygenates, and analyze the reasons related to their catalytic mechanisms, as the production of multi-carbon oxygenates is generally more difficult than that of C1 products. Then we discuss several examples in promoting the photoconversion of CO2 to value-added multi-carbon products in the aspects of photocatalyst design, mass transfer control, determination of active sites, and intermediate regulation. Finally, we summarize perspectives on the challenges and propose potential directions in this fast-developing field, such as the prospect of CO2 transformation to long-chain hydrocarbons like salicylic acid or even plastics.

MA Cation-Induced Diffusional Growth of Low-Bandgap FA-Cs Perovskites Driven by Natural Gradient Annealing.

Low-bandgap formamidinium-cesium (FA-Cs) perovskites of FA1-x Cs x PbI3 (x < 0.1) are promising candidates for efficient and robust perovskite solar cells, but their black-phase crystallization is very sensitive to annealing temperature. Unfortunately, the low heat conductivity of the glass substrate builds up a temperature gradient within from bottom to top and makes the initial annealing temperature of the perovskite film lower than the black-phase crystallization point (~150°C). Herein, we take advantage of such temperature gradient for the diffusional growth of high-quality FA-Cs perovskites by introducing a thermally unstable MA+ cation, which would firstly form α-phase FA-MA-Cs mixed perovskites with low formation energy at the hot bottom of the perovskite films in the early annealing stage. The natural gradient annealing temperature and the thermally unstable MA+ cation then lead to the bottom-to-top diffusional growth of highly orientated α-phase FA-Cs perovskite, which exhibits 10-fold of enhanced crystallinity and reduced trap density (~3.85 × 1015 cm-3). Eventually, such FA-Cs perovskite films were fabricated into stable solar cell devices with champion efficiency up to 23.11%, among the highest efficiency of MA-free perovskite solar cells.

Binderless and Oxygen Vacancies Rich FeNi/Graphitized Mesoporous Carbon/Ni Foam for Electrocatalytic Reduction of Nitrate.

Energy consumption and long-term stability of a cathode are two important aspects of great concern in electrocatalytic nitrate reduction. This work studied a binderless FeNi/graphitized mesoporous carbon directly formed on Ni Foam (FeNi/g-mesoC/NF, 7.3 wt % of Fe) and evaluated its electrocatalytic nitrate reduction performance. We proposed a unique structure model of FeNi/g-mesoC/NF cathode in which FeNi alloy nanoparticles were uniformly embedded in mesoporous carbon and graphitized carbon shells were coated on isolated alloy nanoparticles. Oxygen vacancies (OVs) in FeNi oxide passivating layer facilitate the conversion of NO3--N anions on cathode. Toxic NO2--N was almost undetected due to the synergetic effects of FeNi electrocatalysis, and the NO3--N conversion was high in comparation with ever reported iron-based cathode. The NO3--N conversion showed ultrahigh electrocatalytic stability during one-month-recycling test while the physiochemical properties showed negligible change for FeNi/g-mesoC/NF except the increase of OVs. The energy consumption to treat simulated underground water (50% of NO3--N conversion) was low (0.7 kWh mol-1) for 50 mg L-1 NO3--N. This binderless composite cathode shows great potential in electrocatalytic NO3--N removal in underground water.

2-Aminobenzenethiol-Functionalized Silver-Decorated Nanoporous Silicon Photoelectrodes for Selective CO2 Reduction.

A molecularly thin layer of 2-aminobenzenethiol (2-ABT) was adsorbed onto nanoporous p-type silicon (b-Si) photocathodes decorated with Ag nanoparticles (Ag NPs). The addition of 2-ABT alters the balance of the CO2 reduction and hydrogen evolution reactions, resulting in more selective and efficient reduction of CO2 to CO. The 2-ABT adsorbate layer was characterized by Fourier transform infrared (FTIR) spectroscopy and modeled by density functional theory calculations. Ex situ X-ray photoelectron spectroscopy (XPS) of the 2-ABT modified electrodes suggests that surface Ag atoms are in the +1 oxidation state and coordinated to 2-ABT via Ag-S bonds. Under visible light illumination, the onset potential for CO2 reduction was -50 mV vs. RHE, an anodic shift of about 150 mV relative to a sample without 2-ABT. The adsorption of 2-ABT lowers the overpotentials for both CO2 reduction and hydrogen evolution. A comparison of electrodes functionalized with different aromatic thiols and amines suggests that the primary role of the thiol group in 2-ABT is to anchor the NH2 group near the Ag surface, where it serves to bind CO2 and also to assist in proton transfer.

The Role of Dimethylammonium Iodide in CsPbI3 Perovskite Fabrication: Additive or Dopant?

The controllable growth of CsPbI3 perovskite thin films with desired crystal phase and morphology is crucial for the development of high efficiency inorganic perovskite solar cells (PSCs). The role of dimethylammonium iodide (DMAI) used in CsPbI3 perovskite fabrication was carefully investigated. We demonstrated that the DMAI is an effective volatile additive to manipulate the crystallization process of CsPbI3 inorganic perovskite films with different crystal phases and morphologies. The thermogravimetric analysis results indicated that the sublimation of DMAI is sensitive to moisture, and a proper atmosphere is helpful for the DMAI removal. The time-of-flight secondary ion mass spectrometry and nuclear magnetic resonance results confirmed that the DMAI additive would not alloy into the crystal lattice of CsPbI3 perovskite. Moreover, the DMAI residues in CsPbI3 perovskite can deteriorate the photovoltaic performance and stability. Finally, the PSCs based on phenyltrimethylammonium chloride passivated CsPbI3 inorganic perovskite achieved a record champion efficiency up to 19.03 %.

Thermodynamically stabilized ß-CsPbI3-based perovskite solar cells with efficiencies >18.

Although ß-CsPbI3 has a bandgap favorable for application in tandem solar cells, depositing and stabilizing ß-CsPbI3 experimentally has remained a challenge. We obtained highly crystalline ß-CsPbI3 films with an extended spectral response and enhanced phase stability. Synchrotron-based x-ray scattering revealed the presence of highly oriented ß-CsPbI3 grains, and sensitive elemental analyses-including inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry-confirmed their all-inorganic composition. We further mitigated the effects of cracks and pinholes in the perovskite layer by surface treating with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment between the ß-CsPbI3 absorber layer and carrier-selective contacts. The perovskite solar cells made from the treated material have highly reproducible and stable efficiencies reaching 18.4% under 45 ± 5°C ambient conditions.

Bifunctional Stabilization of All-Inorganic α-CsPbI3 Perovskite for 17% Efficiency Photovoltaics.

The all-inorganic α-CsPbI3 perovskite with the most suitable band gap faces serious challenges of low phase stability and high moisture sensitivity. We discover that a simple phenyltrimethylammonium bromide (PTABr) post-treatment could achieve a bifunctional stabilization including both gradient Br doping (or alloying) and surface passivation. The PTABr treatment on CsPbI3 only induces less than 5 nm blue shift in UV-vis absorbance but significantly stabilize the perovskite phase with much better stability. Finally, the highly stable PTABr treated CsPbI3 based perovskite solar cells exhibit a reproducible photovoltaic performance with a champion efficiency up to 17.06% and stable output of 16.3%. Therefore, this one-step bifunctional stabilization of perovskite through gradient halide doping and surface organic cation passivation presents a novel and promising strategy to design stable and high performance all-inorganic lead halide.

Brand new 1D branched CuO nanowire arrays for efficient photoelectrochemical water reduction.

Developing high surface area nanostructured electrodes with fast charge separation is one of the main challenges for exploring cupric oxide (CuO)-based photocathodes in solar-driven hydrogen production applications. Herein, brand new 1D branched CuO nanowire arrays have been achieved on fluorine-doped tin oxide-coated glass (FTO) through a two-step wet chemical redox reaction. X-ray diffraction patterns, Raman spectra and X-ray photoelectron spectroscopy confirm the pure phase characteristic of the resulting branched CuO. In addition to the enlarged surface area of this advanced functional structure as compared with that of the 1D wire trunk, the charge injection and separation have been improved by rationally controlling the density of defects and size of branches. As a result, the optimized branched CuO exhibits photocurrent as high as 3.6 mA·cm-2 under AM 1.5G (100 mW·cm-2) illumination and 3.0 mA·cm-2 under visible light (λ > 420 nm) at 0.2 V vs. RHE in 0.5 M Na2SO4, which are 2.8- and 3.0-fold greater than those of 1D wire samples, respectively. In addition, the solution-processed approach established herein seems quite favourable for large-scale and low-cost manufacturing.