The selective electrochemical reduction of CO 2 to CO is a promising solution for the design of carbon-neutral, sustainable processes. Achieving a highly selective single reduction product is still challenging because of the energetically favorable competing hydrogen evolution reaction. We report the fabrication of N-doped sponge-like porous graphitic carbon structures embedded with Fe nanoparticles (Fe@NPC) via the pre-modification of a metal-organic framework (IRMOF-3(Zn)) with carboxyferrocene, followed by pyrolysis . The as-prepared Fe@NPC exhibited a 96.4% CO Faradaic efficiency at –0.5 V RHE and good stability. The exceptional CO 2 reduction performance is attributed to the unique structure of the composite catalyst, which provides abundant hierarchical pores that increase CO 2 adsorption and mass transfer, and active Fe sites that synergistically accelerate the kinetics of CO generation. The in situ attenuated total reflectance-Fourier transform infrared analysis provided proof of the improved ability of Fe@NPC to accumulate the crucial intermediate *COOH compared with other pyrolyzed porous carbons. Fe@NPC was used in a Zn-CO 2 battery that delivered a maximum power density of 3.0 mW cm –2 , evidencing its potential for application in energy-converting devices.
Carbon-carbon (C-C) coupling, the rate-determining step in electrocatalytic CO 2 reduction reaction (CO 2 RR) to C 2+ products, has low efficiency and poor stability. It originates from an ineffective water dissociation capability and a high energy barrier for the C-C coupling pathway on existing catalysts. Herein, an efficient and facile Br-CuO electrocatalyst was synthesized to promote water dissociation and achieve an impressive Faradic Efficiency (FE) of around 60% C 2 H 4 at a current density of up to -350 mA/cm 2 with stability of 16 h. Combinative theoretical and experimental protocols strongly evidence that the architecture of Cu 0 -Cu + sites is crucial for the enhancement in CO 2 RR activity. Cu 0 activates CO 2 and Cu + strengthens *CO adsorption to further boost C-C coupling. Furthermore, Br doping can facilitate the dissociation of water to generate *H, which promotes the protonation of *CO to *CHO, thereby enabling the low energy barrier asymmetric *CHO-*CO coupling. The in situ ATR-FTIR and Density functional theory (DFT) was analyzed to explain the reaction mechanism and pathway. This study elucidates the critical function of water dissociation and provides a promising avenue to efficient CO 2 -to-C 2 H 4 electrocatalysis.
Ammonia has been emerging as a sustainable and environmentally friendly fuel. However, direct electrochemical ammonia oxidation reaction (AOR) in low-temperature fuel cells seriously suffers from high overpotential and deficient durability. Herein, rhombic dodecahedron nanoframe of platinum iridium copper (PtIrCu) with high-index faceted hyperbranched nanodendrites (RDNF-HNDs) was developed using a one-step self-etching solvothermal method . The framework structure with the high-index facets enables the PtIrCu nanocrystals to expose more effective active sites. They exhibit an ultra-low onset potential of 0.33 V vs. RHE and high mass activity of 26.1 A g PtIr –1 at 0.50 V, which is 140 mV lower and 7.5 times higher than that of commercial Pt/C in the AOR. In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy verifies that AOR on PtIrCu RDNF-HNDs prefers to the NH x dimerization pathways, effectively alleviating the poison of N ads and NO x . The theoretical calculation also shows that both introducing Cu atoms into PtIr alloy and increasing the content of Ir in PtIrCu alloy can reduce the reaction energy barrier of electrochemical dehydrogenation from *NH 2 to *NH. The specific structure of PtIrCu RDNF-NDs provides a new inspiration to solve the critical issue of electrocatalysts for AOR with low activity and durability.
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