Enhancing C─C Bond Cleavage of Glycerol Electrooxidation Through Spin‐Selective Electron Donation in Pd–PdS ₂ –Co _x Heterostructural Nanosheets

As a 4d transition metal, the spin state of Pd is extremely difficult to directly regulate for the optimized d orbital states owing to the strong spin-orbit coupling effect and further extended d orbital. Herein, we devise a "spin-selective electron donation" strategy to tune specific d orbital electrons of Pd inspired by the Dewar-Chatt-Duncanson model theory. Co-S-Pd bridges with different spin-states of Co^III have been constructed in a series of Pd-PdS₂-Co_x HNSs with tunable Co content. Experiments and theoretical calculations indicate that low-spin Co^III (t_2g ⁶e_g ⁰) with fully occupied t_2g orbitals and empty <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>d</mml:mi> <mml:msup><mml:mi>z</mml:mi> <mml:mn>2</mml:mn></mml:msup> </mml:msub> <mml:annotation>$d_{{z^2}}$</mml:annotation></mml:semantics> </mml:math> orbitals can accurately alter the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>d</mml:mi> <mml:msup><mml:mi>z</mml:mi> <mml:mn>2</mml:mn></mml:msup> </mml:msub> <mml:annotation>$d_{{z^2}}$</mml:annotation></mml:semantics> </mml:math> electron of Pd by σ-donation via the Co-S-Pd bridge. In contrast, the unfilled d_xy orbital of high-spin Co^III (t_2g ⁵e_g ¹) is essential for controlling the d_xy electron of Pd via π-donation. Benefiting from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mi>d</mml:mi> <mml:msup><mml:mi>z</mml:mi> <mml:mn>2</mml:mn></mml:msup> </mml:msub> <mml:annotation>$d_{{z^2}}$</mml:annotation></mml:semantics> </mml:math> state optimization by σ-donation, Pd-PdS₂-Co_4.0 delivers superior performance toward various bio-alcohols (ethanol, ethylene glycol, and glycerol) with enhanced C─C bond cleavage. Furthermore, coupling the glycerol oxidation reaction with the CO₂ reduction reaction (GOR||CO₂RR), the electricity consumption of GOR||CO₂RR drops 46.4% compared to the state-of-art system (OER||CO₂RR). Moreover, anodic Faraday efficiency (FE) of formic acid can be attainable at more than 90% at low voltage regions.