Binary Iron-Manganese Cocatalyst for Simultaneous Activation of C-C and C-O Bonds to Maximally Utilize Lignin for Syngas Generation over InGaN.

Solar-powered lignin reforming offers a carbon-neutral route for syngas production. This study explores a dual non-precious iron-manganese cocatalyst to simultaneously activate both C-C and C-O bonds for maximizing the utilization of various substituents of native lignin to yield syngas. The cocatalyst, integrated with InGaN nanowires on a Si wafer, affords a measurable syngas evolution rate of 42.4 mol g _cat ^-1  h ^-1 from native lignin in distilled water with a high selectivity of 93 % and tunable H ₂ /CO ratios under concentrated light, leading to a considerable light-to-fuel efficiency of 11.8 %. The high FeMn atom efficiency arising from the 1-dimensional nanostructure of InGaN enables the achievement of a high turnover frequency (TOF) of 220896 mol syngas per mol FeMn per hour. Combined experimental and theoretical investigations reveal that the synergetic iron-manganese cocatalyst supported by InGaN nanowires enables simultaneous activation of C-C and C-O bonds with comparable minimized dissociation energies, thus promising to maximally utilize different substituents of -OCH ₃ , and -CH ₂ CH ₂ CH ₃ in lignin for syngas production. Moreover, the dual Fe-Mn cocatalyst demonstrates a most energetically favorable route for the consecutive release of hydrogen from •CH ₃ and •OH by the oxidative holes while inhibiting the reversion of hydrogen and hydroxyl into water.
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