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Isolation of Cu Atoms in Pd Lattice: Forming Highly Selective Sites for Photocatalytic Conversion of CO<sub>2</sub> to CH<sub>4</sub>
Photocatalytic conversion
of CO<sub>2</sub> to CH<sub>4</sub>,
a carbon-neutral fuel, represents an appealing approach to remedy
the current energy and environmental crisis; however, it suffers from
the large production of CO and H<sub>2</sub> by side reactions. The
design of catalytic sites for CO<sub>2</sub> adsorption and activation
holds the key to address this grand challenge. In this Article, we
develop highly selective sites for photocatalytic conversion of CO<sub>2</sub> to CH<sub>4</sub> by isolating Cu atoms in Pd lattice. According
to our synchrotron-radiation characterizations and theoretical simulations,
the isolation of Cu atoms in Pd lattice can play dual roles in the
enhancement of CO<sub>2</sub>-to-CH<sub>4</sub> conversion: (1) providing
the paired Cu–Pd sites for the enhanced CO<sub>2</sub> adsorption
and the suppressed H<sub>2</sub> evolution; and (2) elevating the <i>d</i>-band center of Cu sites for the improved CO<sub>2</sub> activation. As a result, the Pd<sub>7</sub>Cu<sub>1</sub>–TiO<sub>2</sub> photocatalyst achieves the high selectivity of 96% for CH<sub>4</sub> production with a rate of 19.6 μmol g<sub>cat</sub><sup>–1</sup> h<sup>–1</sup>. This work provides fresh
insights into the catalytic site design for selective photocatalytic
CO<sub>2</sub> conversion, and highlights the importance of catalyst
lattice engineering at atomic precision to catalytic performance