Efficient CO2 Electroreduction via Au-Complex Derived Carbon Nanotube Supported Au Nanoclusters

Synthesis and Electrochemical Study of Gold(I) Carbene Complexes

In this work, we have prepared and characterized some gold compounds wearing a N-heterocyclic carbene (NHC) ligand as well as alkynyl derivatives with different substituents. The study of their electrochemical behavior reveals that these complexes show an irreversible wave at potentials ranging between -2.79 and -2.91 V, referenced to the ferrocenium/ferrocene pair. DFT calculations indicate that the reduction occurs mainly on the aryl-C≡C fragment. The cyclic voltammetry experiments under CO2 atmosphere show an increase in the faradaic current of the reduction wave compared to the experiments under argon atmosphere, indicating a possible catalytic activity towards the carbon dioxide reduction reaction (CO2RR).

Au-Based Bimetallic Catalysts for Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid under Base-Free Reaction Conditions

The aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) plays a pivotal role in the synthesis of renewable, biodegradable plastics and sustainable chemicals. Although supported gold nanoclusters (NCs) exhibit significant potential in this process, they often suffer from low selectivity. To address this challenge, a series of gold-M (M means Ni, Fe, Cu, and Pd) bimetallic NCs catalysts were designed and synthesized to facilitate the selective oxidation of HMF to FDCA. Our findings indicate that the introduction of doped metals, particularly Ni and Pd, not only improves the reaction rates for HMF tandem oxidation but also promotes high yields of FDCA. Various characterizations techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption (CO-DRIFTS), and temperature-programmed desorption of oxygen (O2-TPD), were employed to scrutinize the structural and electronic properties of the prepared catalysts. Notably, an electronic effect was observed across the Au-based bimetallic catalysts, facilitating the activation of reactant molecules and enhancing the catalytic performance. This study provides valuable insights into the alloy effects, aiding in the development of highly efficient Au-based bimetallic catalysts for biomass conversions.

Improving Stability of CO2 Electroreduction by Incorporating Ag NPs in N-Doped Ordered Mesoporous Carbon Structures

The electroreduction of carbon dioxide (eCO2RR) to CO using Ag nanoparticles as an electrocatalyst is promising as an industrial carbon capture and utilization (CCU) technique to mitigate CO2 emissions. Nevertheless, the long-term stability of these Ag nanoparticles has been insufficient despite initial high Faradaic efficiencies and/or partial current densities. To improve the stability, we evaluated an up-scalable and easily tunable synthesis route to deposit low-weight percentages of Ag nanoparticles (NPs) on and into the framework of a nitrogen-doped ordered mesoporous carbon (NOMC) structure. By exploiting this so-called nanoparticle confinement strategy, the nanoparticle mobility under operation is strongly reduced. As a result, particle detachment and agglomeration, two of the most pronounced electrocatalytic degradation mechanisms, are (partially) blocked and catalyst durability is improved. Several synthesis parameters, such as the anchoring agent, the weight percentage of Ag NPs, and the type of carbonaceous support material, were modified in a controlled manner to evaluate their respective impact on the overall electrochemical performance, with a strong emphasis on operational stability. The resulting powders were evaluated through electrochemical and physicochemical characterization methods, including X-ray diffraction (XRD), N2-physisorption, Inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy (SEM-EDS), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM-EDS, electron tomography, and X-ray photoelectron spectroscopy (XPS). The optimized Ag/soft-NOMC catalysts showed both a promising selectivity (∼80%) and stability compared with commercial Ag NPs while decreasing the loading of the transition metal by more than 50%. The stability of both the 5 and 10 wt % Ag/soft-NOMC catalysts showed considerable improvements by anchoring the Ag NPs on and into a NOMC framework, resulting in a 267% improvement in CO selectivity after 72 h (despite initial losses) compared to commercial Ag NPs. These results demonstrate the promising strategy of anchoring Ag NPs to improve the CO selectivity during prolonged experiments due to the reduced mobility of the Ag NPs and thus enhanced stability.

Synthesis of 2H/fcc-Heterophase AuCu Nanostructures for Highly Efficient Electrochemical CO2 Reduction at Industrial Current Densities

Structural engineering of nanomaterials offers a promising way for developing high-performance catalysts toward catalysis. However, the delicate modulation of thermodynamically unfavorable nanostructures with unconventional phases still remains a challenge. Here, the synthesis of hierarchical AuCu nanostructures is reported with hexagonal close-packed (2H-type)/face-centered cubic (fcc) heterophase, high-index facets, planar defects (e.g., stacking faults, twin boundaries, and grain boundaries), and tunable Cu content. The obtained 2H/fcc Au99 Cu1 hierarchical nanosheets exhibit excellent performance for the electrocatalytic CO2 reduction to produce CO, outperforming the 2H/fcc Au91 Cu9 and fcc Au99 Cu1 . The experimental results, especially those obtained by in-situ differential electrochemical mass spectroscopy and attenuated total reflection Fourier-transform infrared spectroscopy, suggest that the enhanced catalytic performance of 2H/fcc Au99 Cu1 arises from the unconventional 2H/fcc heterophase, high-index facets, planar defects, and appropriate alloying of Cu. Impressively, the 2H/fcc Au99 Cu1 shows CO Faradaic efficiencies of 96.6% and 92.6% at industrial current densities of 300 and 500 mA cm-2 , respectively, as well as good durability, placing it among the best CO2 reduction electrocatalysts for CO production. The atomically structural regulation based on phase engineering of nanomaterials (PEN) provides an avenue for the rational design and preparation of high-performance electrocatalysts for various catalytic applications.

Bibliometric review of carbon neutrality with CiteSpace: evolution, trends, and framework

The concept of carbon neutrality has been promoted and implemented in increasing countries since the twenty-first century. In-depth research on carbon neutrality has helped improve the environmental conditions and played a particular role in sustaining economic and social development. However, there is a less comprehensive review of the status in this field; therefore, this article uses the information visualization software CiteSpace to thoroughly analyze carbon neutrality research from multiple perspectives. This study aims to reveal the current research evolutions and hotspots in this field, predict future research trends, and construct the framework for better understanding. The results find that the number of papers published on carbon neutrality keeps increasing annually, and carbon neutrality has been the widely participated domain. In addition, publications by organizations and in top journals have aroused wide attention, and the hot spots on carbon neutrality have shifted to policy, recovery, and efficiency. Based on the results, a knowledge framework of this domain is constructed to give readers a clearer understanding of the evolvement and trends, which will also provide targeted references and help for future researchers.