Abstract
Developing effective catalysts based on earth abundant elements is critical for CO2 electroreduction. However, simultaneously achieving a high Faradaic efficiency (FE) and high current density of CO (jCO) remains a challenge. Herein, we prepare a Mn single-atom catalyst (SAC) with a Mn-N3 site embedded in graphitic carbon nitride. The prepared catalyst exhibits a 98.8% CO FE with a jCO of 14.0 mA cm−2 at a low overpotential of 0.44 V in aqueous electrolyte, outperforming all reported Mn SACs. Moreover, a higher jCO of 29.7 mA cm−2 is obtained in an ionic liquid electrolyte at 0.62 V overpotential. In situ X-ray absorption spectra and density functional theory calculations demonstrate that the remarkable performance of the catalyst is attributed to the Mn-N3 site, which facilitates the formation of the key intermediate COOH* through a lowered free energy barrier.
Highlights
Developing effective catalysts based on earth abundant elements is critical for CO2 electroreduction
Mn–C3N4/carbon nanotubes (CNTs) was synthesized through thermal pyrolysis of Mn acetate, CNTs, and dicyandiamide (DCD) under nitrogen at 873 K followed by hydrochloric acid washing, and the addition of CNTs served to improve the g-C3N4 conductivity
Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that Mn–C3N4/CNT maintains the morphology of the CNTs without the formation of obvious particles (Fig. 1a, b)
Summary
Developing effective catalysts based on earth abundant elements is critical for CO2 electroreduction. We prepare a Mn single-atom catalyst (SAC) with a Mn-N3 site embedded in graphitic carbon nitride. Novel catalysts are strongly desirable to simultaneously obtain a high Faradaic efficiency (FE) and high current density of target products[3]. The prepared catalyst displayed a 98.8% CO FE with a jCO of 14.0 mA cm−2 at a low overpotential of 0.44 V in aqueous electrolyte, which outperforms all Mn SACs reported in the literature. In situ X-ray absorption spectra and density functional theory (DFT) calculations were conducted to investigate the process of CO2 adsorption, activation and conversion over Mn–C3N4/CNT, demonstrating that three N atoms coordinated to a Mn center in g-C3N4 can greatly improve the performance of the Mn SAC in the CO2RR. This work shows a means to enhance the CO2RR performance of Mn-based catalysts under mild conditions
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