Extrinsic hydrophobicity-controlled silver nanoparticles as efficient and stable catalysts for CO2 electrolysis

To realize economically feasible electrochemical CO2 conversion, achieving a high partial current density for value-added products is particularly vital. However, acceleration of the hydrogen evolution reaction due to cathode flooding in a high-current-density region makes this challenging. Herein, we find that partially ligand-derived Ag nanoparticles (Ag-NPs) could prevent electrolyte flooding while maintaining catalytic activity for CO2 electroreduction. This results in a high Faradaic efficiency for CO (>90%) and high partial current density (298.39 mA cm‒2), even under harsh stability test conditions (3.4 V). The suppressed splitting/detachment of Ag particles, due to the lipid ligand, enhance the uniform hydrophobicity retention of the Ag-NP electrode at high cathodic overpotentials and prevent flooding and current fluctuations. The mass transfer of gaseous CO2 is maintained in the catalytic region of several hundred nanometers, with the smooth formation of a triple phase boundary, which facilitate the occurrence of CO2RR instead of HER. We analyze catalyst degradation and cathode flooding during CO2 electrolysis through identical-location transmission electron microscopy and operando synchrotron-based X-ray computed tomography. This study develops an efficient strategy for designing active and durable electrocatalysts for CO2 electrolysis.

Multiscale CO2 Electrocatalysis to C2+ Products: Reaction Mechanisms, Catalyst Design, and Device Fabrication

Electrosynthesis of value-added chemicals, directly from CO2, could foster achievement of carbon neutral through an alternative electrical approach to the energy-intensive thermochemical industry for carbon utilization. Progress in this area, based on electrogeneration of multicarbon products through CO2 electroreduction, however, lags far behind that for C1 products. Reaction routes are complicated and kinetics are slow with scale up to the high levels required for commercialization, posing significant problems. In this review, we identify and summarize state-of-art progress in multicarbon synthesis with a multiscale perspective and discuss current hurdles to be resolved for multicarbon generation from CO2 reduction including atomistic mechanisms, nanoscale electrocatalysts, microscale electrodes, and macroscale electrolyzers with guidelines for future research. The review ends with a cross-scale perspective that links discrepancies between different approaches with extensions to performance and stability issues that arise from extensions to an industrial environment.

Intra-Organ Delivery of Nanotherapeutics for Organ Transplantation

Targeted delivery of therapeutics through the use of nanoparticles (NPs) has emerged as a promising method that increases their efficacy and reduces their side effects. NPs can be tailored to localize to selective tissues through conjugation to ligands that bind cell-specific receptors. Although the vast majority of nanodelivery platforms have focused on cancer therapy, efforts have begun to introduce nanotherapeutics to the fields of immunology as well as transplantation. In this review, we provide an overview from a clinician's perspective of current nanotherapeutic strategies to treat solid organ transplants with NPs during the time interval between organ harvest from the donor and placement into the recipient, an innovative technology that can provide major benefits to transplant patients. The use of ex vivo normothermic machine perfusion (NMP), which is associated with preserving the function of the organ following transplantation, also provides an ideal opportunity for a localized, sustained, and controlled delivery of nanotherapeutics to the organ during this critical time period. Here, we summarize previous endeavors to improve transplantation outcomes by treating the organ with NPs prior to placement in the recipient. Investigations in this burgeoning field of research are promising, but more extensive studies are needed to overcome the physiological challenges to achieving effective nanotherapeutic delivery to transplanted organs discussed in this review.

Improved Interface Charge Transfer and Redistribution in CuO-CoOOH p-n Heterojunction Nanoarray Electrocatalyst for Enhanced Oxygen Evolution Reaction

Electron density modulation is of great importance in an attempt to achieve highly active electrocatalysts for the oxygen evolution reaction (OER). Here, the successful construction of CuO@CoOOH p-n heterojunction (i.e., p-type CuO and n-type CoOOH) nanoarray electrocatalyst through an in situ anodic oxidation of CuO@CoSx on copper foam is reported. The p-n heterojunction can remarkably modify the electronic properties of the space-charge region and facilitate the electron transfer. Moreover, in situ Raman study reveals the generation of SO4 2- from CoSx oxidation, and electron cloud density distribution and density functional theory calculation suggest that surface-adsorbed SO4 2- can facilitate the OER process by enhancing the adsorption of OH- . The positively charged CoOOH in the space-charge region can significantly enhance the OER activity. As a result, the CuO@CoOOH p-n heterojunction shows significantly enhanced OER performance with a low overpotential of 186 mV to afford a current density of 10 mA cm-2 . The successful preparation of a large scale (14 × 25 cm2 ) sample demonstrates the possibility of promoting the catalyst to industrial-scale production. This study offers new insights into the design and fabrication of non-noble metal-based p-n heterojunction electrocatalysts as effective catalytic materials for energy storage and conversion.

Versatile Interfacial Self-Assembly of Ti3C2Tx MXene Based Composites with Enhanced Kinetics for Superior Lithium and Sodium Storage

Exploring nanostructured transition-metal sulfide anode materials with excellent electrical conductivity is the key point for high-performance alkali metal ion storage devices. Herein, we propose a powerful bottom-up strategy for the construction of a series of sandwich-structured materials by a rapid interfacial self-assembly approach. Oleylamine could act as a functional reagent to guarantee that the nanomaterials self-assemble with MXene. Benefiting from the small size of Co-NiS nanorods, excellent conductivity of MXene, and sandwiched structure of the composite, the Co-NiS/MXene composite could deliver a high discharge capacity of 911 mAh g^-1 at 0.1 A g^-1 for lithium-ion storage. After 200 cycles at 0.1 A g^-1, a high specific capacity of 1120 mAh g^-1 could be still remaining, indicating excellent cycling stability. For sodium-ion storage, the composite exhibits high specific capacity of 541 mAh g^-1 at 0.1 A g^-1 and excellent rate capability (263 mAh g^-1 at 5 A g^-1). This work offers a straightforward strategy to design and construct MXene-based anode nanomaterials with sandwiched structure for high-performance alkali metal ion storage and even in other fields.

Enhanced selectivity and stability towards CO2 reduction of sub-5 nm Au NPs derived from supramolecular assembly

We report three well-defined types of Au nanoparticles (NPs) protected by rigid macrocyclic cucurbit[n]uril (CB[n]) (CB[n]-Au), which are prepared via the supramolecular self-assembly of the precursors. CB[n]-Au shows excellent catalytic activity and selectivity, with a performance that can be maintained for up to 72 h in the electroreduction of CO₂ to CO. The effects of the structural features of different CB[n]s on the electrocatalytic performance of the Au NPs have been revealed for the first time.

Inside-mode indium oxide/carbon nanotubes for efficient carbon dioxide electroreduction by suppressing hydrogen evolution

The hydrogen evolution reaction is a huge challenge for CO2 electroreduction. Herein, an inside-mode indium oxide/carbon nanotube compound (MWCNTs@In2O3) is developed to maximize the catalytic effect and suppress hydrogen evolution, its HCOOH selectivity can reach up to 92.2% at -16.8 mA cm-2, which is more efficient than In2O3.

Copper sulfide as the cation exchange template for synthesis of bimetallic catalysts for CO2 electroreduction

Among metals used for CO₂ electroreduction in water, Cu appears to be unique in its ability to produce C2+ products like ethylene. Bimetallic combinations of Cu with other metals have been investigated with the goal of steering selectivity via creating a tandem pathway through the CO intermediate or by changing the surface electronic structure. Here, we demonstrate a facile cation exchange method to synthesize Ag/Cu electrocatalysts for CO₂ reduction using Cu sulfides as a growth template. Beginning with Cu_2−xS nanosheets (C-nano-0, 100 nm lateral dimension, 14 nm thick), varying the Ag⁺ concentration in the exchange solution produces a gradual change in crystal structure from Cu₇S₄ to Ag₂S, as the Ag/Cu mass ratio varies from 0.3 to 25 (CA-nano-x, x indicating increasing Ag fraction). After cation exchange, the nanosheet morphology remains but with increased shape distortion as the Ag fraction is increased. Interestingly, the control (C-nano-0) and cation exchanged nanosheets have very high faradaic efficiency for producing formate at low overpotential (−0.2 V vs. RHE). The primary effect of Ag incorporation is increased production of C2+ products at −1.0 V vs. RHE compared with C-nano-0, which primarily produces formate. Cation exchange can also be used to modify the surface of Cu foils. A two-step electro-oxidation/sulfurization process was used to form Cu sulfides on Cu foil (C-foil-x) to a depth of a few 10 s of microns. With lower Ag⁺ concentrations, cation exchange produces uniformly dispersed Ag; however, at higher concentrations, Ag particles nucleate on the surface. During CO₂ electroreduction testing, the product distribution for Ag/Cu sulfides on Cu foil (CA-foil-x-y) changes in time with an initial increase in ethylene and methane production followed by a decrease as more H₂ is produced. The catalysts undergo a morphology evolution towards a nest-like structure which could be responsible for the change in selectivity. For cation-exchanged nanosheets (CA-nano-x), pre-reduction at negative potentials increases the CO₂ reduction selectivity compared to tests of as-synthesized material, although this led to the aggregation of nanosheets into filaments. Both types of bimetallic catalysts are capable of selective reduction of CO₂ to multi-carbon products, although the optimal configurations appear to be metastable.

Cu sulfides as a template for Ag/Cu sulfide catalysts for electrochemical CO₂. With the introduction of Ag, nanosheet show increased C2+ product generation. The catalysts undergo a morphology evolution as CO₂ reduction proceeds.

Transition metal-based catalysts for the electrochemical CO2 reduction: from atoms and molecules to nanostructured materials

An overview of the main strategies for the rational design of transition metal-based catalysts for the electrochemical conversion of CO₂, ranging from molecular systems to single-atom and nanostructured catalysts.