g‑C<sub>3</sub>N<sub>4</sub>@α-Fe<sub>2</sub>O<sub>3</sub>/C Photocatalysts: Synergistically Intensified Charge Generation and Charge Transfer for NADH Regeneration


Graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) is an emergent metal-free photocatalyst because of its band position, natural abundance, and facile preparation. Synergetic intensification of charge generation and charge transfer of g-C<sub>3</sub>N<sub>4</sub> to increase solar-to-chemical efficiency remains a hot yet challenging issue. Herein, a nanoshell with two moieties of α-Fe<sub>2</sub>O<sub>3</sub> and carbon (C) is in situ formed on the surface of a g-C<sub>3</sub>N<sub>4</sub> core through calcination of Fe<sup>3+</sup>/polyphenol-coated melamine, thus acquiring g-C<sub>3</sub>N<sub>4</sub>@α-Fe<sub>2</sub>O<sub>3</sub>/C core@shell photocatalysts. The α-Fe<sub>2</sub>O<sub>3</sub> moiety acts as an additional photosensitizer, offering more photogenerated electrons, whereas the C moiety bridges a “highway” to facilitate the electron transfer either from α-Fe<sub>2</sub>O<sub>3</sub> moiety to g-C<sub>3</sub>N<sub>4</sub> or from g-C<sub>3</sub>N<sub>4</sub> to C moiety. By tuning the proportion of these two moieties in the nanoshell, a photocurrent density of 3.26 times higher than pristine g-C<sub>3</sub>N<sub>4</sub> is obtained. When utilized for photocatalytic regeneration of reduced nicotinamide adenine dinucleotide (NADH, a dominant cofactor in biohydrogenation reaction), g-C<sub>3</sub>N<sub>4</sub>@α-Fe<sub>2</sub>O<sub>3</sub>/C exhibits an equilibrium NADH yield of 76.3% with an initial reaction rate (<i>r</i>) of 7.7 mmol h<sup>–1</sup> g<sup>–1</sup>, among the highest <i>r</i> for photocatalytic NADH regeneration ever reported. Manipulating the coupling between charge generation and charge transfer may offer a facile, generic strategy to improve the catalytic efficiency of a broad range of photocatalysts other than g-C<sub>3</sub>N<sub>4</sub>

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