Abstract
Electrochemical CO2 reduction (CO2RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings. In this study, the effect of conducting support on the CO2RR behaviors of semi-conductive metal-organic framework (MOF) — Cu3(HITP)2 are carefully investigated. Compared to the stand-alone MOF, adding Ketjen Black greatly promotes C2H4 production with a stabilized Faradaic efficiency between 60-70% in a wide potential range and prolonged period. Multicrystalline Cu nano-crystallites in the reconstructed MOF are induced and stabilized by the conducting support via current shock and charge delocalization, which is analogous to the mechanism of dendrite prevention through conductive scaffolds in metal ion batteries. Density functional theory calculations elucidate that the contained multi-facets and rich grain boundaries promote C–C coupling while suppressing HER. This study underlines the key role of substrate-catalyst interaction, and the regulation of Cu crystalline states via conditioning the charge transport, in steering the CO2RR pathway.
Highlights
Electrochemical CO2 reduction (CO2RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings
We found that adding Ketjen Black (KB) enabled greatly promoting the C2H4 production with stabilized Faradaic efficiency (FE) between 60 and 70% in a wide potential range and prolonged testing period, whereas the stand-alone metal-organic framework (MOF) yielded more mixed reduction products
X-ray photoelectron spectroscopy of Cu 2p3/2 exhibited a mixture of Cu2+ (933.5 eV) and Cu+ (931.8 eV) states in Cu3(HITP)[2] (Supplementary Fig. 2)[31], which was further corroborated by the X-ray absorption near edge structure (XANES, Supplementary Fig. 3)
Summary
Electrochemical CO2 reduction (CO2RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings. The effect of conducting support on the CO2RR behaviors of semi-conductive metal-organic framework (MOF) — Cu3(HITP)[2] are carefully investigated. Previous studies showed that the substrates for catalyst loading, in most cases the carbon support, play a critical role in steering the CO2RR pathway and stabilizing the catalytic process[19,20]. By pre-reducing the Cu nodes in a conductive metal organic framework (MOF) (CuHHTP) into Cu2O quantum dots, Cao and co-workers achieved a high selectivity of CH4 formation, which was attributed to ample hydrogen bonding from the substrate in stabilizing key intermediates[23]. It is vitally important to assess the effect of carbon support on CO2RR and scrutinize the substrate–catalyst interaction, as well as the charge transport behavior, for a better mechanistic understanding
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