26. Atomically Dispersed Pt-N3C1 Sites Enabling Efficient and Selective Electrocatalytic C-C Bond Cleavage in Lignin Models under Ambient Conditions

Cui, T., Ma, L., Wang, S., Ye, C., Liang, X., Zhang, Z., Meng, G., Zheng, L., Hu, H. S., Zhang, J.*, Duan, H.*, Wang, D.*, Li, Y.
J. Am. Chem. Soc. 2021, 143 (25), 9429-9439.
DOI: 10.1021/jacs.1c02328

Abstract
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–N₃C₁ sites planted on nitrogen-doped carbon nanotubes (Pt₁/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. Pt₁/N-CNTs exhibits 99% substrate conversion with 81% yield of benzaldehyde, which is exceptional and unprecedented compared with previously reported electrocatalysts. Moreover, Pt₁/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 Pt₁/N-CNTs arises from the atomically dispersed Pt–N₃C₁ 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.