Platinum is the most efficient catalyst for hydrogen evolution reaction in acidic conditions, but its widespread use has been impeded by scarcity and high cost. Herein, Pt atomic clusters (Pt ACs) containing Pt-O-Pt units were prepared using Co/N co-doped carbon (CoNC) as support. Pt ACs are anchored to single Co atoms on CoNC by forming strong interactions. Pt-ACs/CoNC exhibits only 24 mV overpotential at 10 mA cm−2 and a high mass activity of 28.6 A mg−1 at 50 mV, which is more than 6 times higher than commercial Pt/C with any Pt loadings. Spectroscopic measurements and computational modeling reveal the enhanced hydrogen generation activity attributes to the charge redistribution between Pt and O atoms in Pt-O-Pt units, making Pt atoms the main active sites and O linkers the assistants, thus optimizing the proton adsorption and hydrogen desorption. This work opens an avenue to fabricate noble-metal-based ACs stabilized by single-atom catalysts with desired properties for electrocatalysis.
Three-dimensional Bi 2 O 3 fractal nanostructures (f-Bi 2 O 3) were directly self-assembled on carbon fiber papers (CFP) using a scalable hot-aerosol synthesis strategy. This approach provides high versatility in modulating the physiochemical properties of the Bi 2 O 3 catalyst by a tailorable control of its crystalline size, loading, electron density as well as providing exposed stacking of the nanomaterials on the porous CFP substrate. As a result, when tested for electrochemical CO 2 reduction reactions (CO 2 RR), these f-Bi 2 O 3 electrodes demonstrated superior conversion of CO 2 to formate (HCOO-) with low onset overpotential and a high mass-specific formate partial current density of-52.2 mA mg-1 , which is ~ 3 times higher than that of the drop-casted control Bi 2 O 3 catalyst (-15.5 mA mg-1), and a high Faradaic This article is protected by copyright. All rights reserved. efficiency (FE HCOO-) of 87% at an applied potential of-1.2 V vs reversible hydrogen electrode (RHE). Our findings reveal that the high exposure of roughened -phase Bi 2 O 3 /Bi edges and the improved electron density of these fractal structures are key contributors in attainment of high CO 2 RR activity.
In this study, we propose a top-down approach for the controlled preparation of undercoordinated Ni–N x (Ni-hG) and Fe–N x (Fe-hG) catalysts within a holey graphene framework, for the electrochemical CO2 reduction reaction (CO2RR) to synthesis gas (syngas). Through the heat treatment of commercial-grade nitrogen-doped graphene, we prepared a defective holey graphene, which was then used as a platform to incorporate undercoordinated single atoms via carbon defect restoration, confirmed by a range of characterization techniques. We reveal that these Ni-hG and Fe-hG catalysts can be combined in any proportion to produce a desired syngas ratio (1–10) across a wide potential range (−0.6 to −1.1 V vs RHE), required commercially for the Fischer–Tropsch (F–T) synthesis of liquid fuels and chemicals. These findings are in agreement with our density functional theory calculations, which reveal that CO selectivity increases with a reduction in N coordination with Ni, while unsaturated Fe–N x sites favor the hydrogen evolution reaction (HER). The potential of these catalysts for scale up is further demonstrated by the unchanged selectivity at elevated temperature and stability in a high-throughput gas diffusion electrolyzer, displaying a high-mass-normalized activity of 275 mA mg–1 at a cell voltage of 2.5 V. Our results provide valuable insights into the implementation of a simple top-down approach for fabricating active undercoordinated single atom catalysts for decarbonized syngas generation.
Engineering the metal−carbon heterointerface has become an increasingly important route toward achieving cost-effective and highperforming electrocatalysts. The specific properties of graphene edge sites, such as the high available density of states and extended unpaired π-bonding, make it a promising candidate to tune the electronic properties of metal catalysts. However, to date, understanding and leveraging graphene edge− metal catalysts for improved electrocatalytic performance remains largely elusive. Herein, edge-rich vertical graphene (er-VG) was synthesized and used as a catalyst support for Ni−Fe hydroxides for the oxygen evolution reaction (OER). The hybrid Ni−Fe/er-VG catalyst exhibits excellent OER performance with a mass current of 4051 A g −1 (at overpotential η = 300 mV) and turnover frequency (TOF) of 4.8 s −1 (η = 400 mV), outperforming Ni−Fe deposited on pristine VG and other metal foam supports. Angle-dependent X-ray absorption spectroscopy shows that the edge-rich VG support can preferentially template Fe−O units with a specific valence orbital alignment interacting with the unoccupied density of states on the graphene edges. This graphene edge−metal interaction was shown to facilitate the formation of undersaturated and strained Fe-sites with high valence states, while promoting the formation of redox-activated Ni species, thus improving OER performance. These findings demonstrate rational design of the graphene edge−metal interface in electrocatalysts which can be used for various energy conversion and chemical synthesis reactions.
Three-dimensional (3D) fractal structure of Au–Bi2O3 is fabricated and shows excellent multifunctional performance towards CO2 reduction and optical gas sensing.
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