Synergistic Effects of Amine Functional Groups and Enriched-Atomic-Iron Sites in Carbon Dots for Industrial-Current-Density CO2 Electroreduction.

Metal phthalocyanine molecules with Me-N4 centers have shown promise in electrocatalytic CO2 reduction (eCO2R) for CO generation. However, iron phthalocyanine (FePc) is an exception, exhibiting negligible eCO2R activity due to a higher CO2 to *COOH conversion barrier and stronger *CO binding energy. Here, amine functional groups onto atomic-Fe-rich carbon dots (Af-Fe-CDs) are introduced via a one-step solvothermal molecule fusion approach. Af-Fe-CDs feature well-defined Fe-N4 active sites and an impressive Fe loading (up to 8.5 wt%). The synergistic effect between Fe-N4 active centers and electron-donating amine functional groups in Af-Fe-CDs yielded outstanding CO2-to-CO conversion performance. At industrial-relevant current densities exceeding 400 mA cm-2 in a flow cell, Af-Fe-CDs achieved >92% selectivity, surpassing state-of-the-art CO2-to-CO electrocatalysts. The in situ electrochemical FTIR characterization combined with theoretical calculations elucidated that Fe-N4 integration with amine functional groups in Af-Fe-CDs significantly reduced energy barriers for *COOH intermediate formation and *CO desorption, enhancing eCO2R efficiency. The proposed synergistic effect offers a promising avenue for high-efficiency catalysts with elevated atomic-metal loadings.

Carbon Catalysts Empowering Sustainable Chemical Synthesis via Electrochemical CO2 Conversion and Two-Electron Oxygen Reduction Reaction.

Carbon materials hold significant promise in electrocatalysis, particularly in electrochemical CO2 reduction reaction (eCO2 RR) and two-electron oxygen reduction reaction (2e- ORR). The pivotal factor in achieving exceptional overall catalytic performance in carbon catalysts is the strategic design of specific active sites and nanostructures. This work presents a comprehensive overview of recent developments in carbon electrocatalysts for eCO2 RR and 2e- ORR. The creation of active sites through single/dual heteroatom doping, functional group decoration, topological defect, and micro-nano structuring, along with their synergistic effects, is thoroughly examined. Elaboration on the catalytic mechanisms and structure-activity relationships of these active sites is provided. In addition to directly serving as electrocatalysts, this review explores the role of carbon matrix as a support in finely adjusting the reactivity of single-atom molecular catalysts. Finally, the work addresses the challenges and prospects associated with designing and fabricating carbon electrocatalysts, providing valuable insights into the future trajectory of this dynamic field.

NBOH Site-Activated Graphene Quantum Dots for Boosting Electrochemical Hydrogen Peroxide Production.

Carbon materials are considered promising 2/4 e- oxygen reduction reaction (ORR) electrocatalysts for synthesizing H2 O2 /H2 O via regulating heteroatom dopants and functionalization. Here, various doped and functionalized graphene quantum dots (GQDs) are designed to reveal the crucial active sites of carbon materials for ORR to produce H2 O2 . Density functional theory (DFT) calculations predict that the edge structure involving edge N, B dopant pairs and further OH functionalization to the B (NBOH) is an active center for 2e- ORR. To verify the above predication, GQDs with an enriched density of NBOH (NBO-GQDs) are designed and synthesized by the hydrothermal reaction of NH2 edge-functionalized GQDs with H3 BO3 forming six-member heterocycle containing the NBOH structure. When dispersed on conductive carbon substrates, the NBO-GQDs show H2 O2 selectivity of over 90% at 0.7 -0.8 V versus reversible hydrogen electrode in the alkaline solution in a rotating ring-disk electrode setup. The selectivity retains 90% of the initial value after 12 h stability test. In a flow cell setup, the H2 O2 production rate is up to 709 mmol gcatalyst -1  h-1 , superior to most reported carbon- and metal-based electrocatalysts. This work provides molecular insight into the design and formulation of highly efficient carbon-based catalysts for sustainable H2 O2 production.

Structure-Tailored Surface Oxide on Cu-Ga Intermetallics Enhances CO2 Reduction Selectivity to Methanol at Ultralow Potential.

Electrochemical CO2 reduction reaction (eCO2 RR) is performed on two intermetallic compounds formed by copper and gallium metals (CuGa2 and Cu9 Ga4 ). Among them, CuGa2 selectively converts CO2 to methanol with remarkable Faradaic efficiency of 77.26% at an extremely low potential of -0.3 V vs RHE. The high performance of CuGa2 compared to Cu9 Ga4 is driven by its unique 2D structure, which retains surface and subsurface oxide species (Ga2 O3 ) even in the reduction atmosphere. The Ga2 O3 species is mapped by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) techniques and electrochemical measurements. The eCO2 RR selectivity to methanol are decreased at higher potential due to the lattice expansion caused by the reduction of the Ga2 O3 , which is probed by in situ XAFS, quasi in situ powder X-ray diffraction, and ex situ XPS measurements. The mechanism of the formation of methanol is visualized by in situ infrared (IR) spectroscopy and the source of the carbon of methanol at the molecular level is confirmed from the isotope-labeling experiments in presence of 13 CO2 . Finally, to minimize the mass transport limitations and improve the overall eCO2 RR performance, a poly(tetrafluoroethylene)-based gas diffusion electrode is used in the flow cell configuration.

Unraveling the Role of Site Isolation and Support for Semihydrogenation of Phenylacetylene.

Intermetallic compounds (IMCs) composed of transition metals and post-transition metals function as superior heterogeneous catalysts in comparison to their monometallic and bimetallic alloy counterparts. Rendering IMCs in their nanomaterial iterations further enhances their efficiency. Herein, we demonstrate the role of PdIn as well-dispersed intermetallic nanoparticles (IMNPs) for the semihydrogenation of phenylacetylene selectively to styrene at ambient conditions. Higher selectivity of PdIn was explained with the help DOS calculations. We have explored the role of a few well-known silica-based supports such as SBA-15 and MCM-41, providing insight into how they affect catalysis. As an additional support we have explored previously reported JNC-1, a mesoporous carbon material obtained via a templated strategy using SBA-15. PdIn supported on SBA-15 and JNC-1 displayed the best dispersion, while also exhibiting the most catalytic activity due to the unique nature of the porous structure.