Atomically Dispersed Pt-N_3C_1 Sites Enabling Efficient and Selective Electrocatalytic C-C Bond Cleavage in Lignin Models under Ambient Conditions

摘要

Selective cleavage of C-C linkages is the key and a challenge for lignin degradation to harvest value-added aromatic compounds. To this end, electrocatalytic oxidation presents a promising technique by virtue of mild reaction conditions and strong sustainability. However, the existing electrocatalysts (traditional bulk metal and metal oxides) for C-C bond oxidative cleavage suffer from poor selectivity and low product yields. We show for the first time that atomically dispersed Pt-N_3C_1 sites planted on nitrogen-doped carbon nanotubes (Pt_1/N-CNTs), constructed via a stepwise polymerization-carbonization-electrostatic adsorption strategy, are highly active and selective toward C_α-C_β bond cleavage in β-O-4 model compounds under ambient conditions. Pt_1/N-CNTs exhibits 99% substrate conversion with 81% yield of benzaldehyde, which is exceptional and unprecedented compared with previously reported electrocatalysts. Moreover, Pt_1/N-CNTs using only 0.41 wt % Pt achieved a much higher benzaldehyde yield than those of the state-of-the-art bulk Pt electrode (100 wt % Pt) and commercial Pt/C catalyst (20 wt % Pt). Systematic experimental investigation together with density functional theory (DFT) calculation suggests that the superior performance of Pt_1/N-CNTs arises from the atomically dispersed Pt-N_3C_1 sites facilitating the formation of a key C_β radical intermediate, further inducing a radical/radical cross-coupling path to break the C_α-C_β bond. This work opens up opportunities in lignin valorization via a green and sustainable electrochemical route with ultralow noble metal usage.