Study of the Photoinduced Charge Injection in the Reaction Intermediate of the Dehydrogenation of Formic Acid on Palladium

The production rate of hydrogen from formic acid on palladium is enhanced in the presence of an Au nanorod by irradiating the system at its plasmon frequency. Taking inspiration from this, we study here the effect of the shape of the Pd cluster (from Pd(111)) on the photoinduced charge injection into the HCOO moiety and adsorbed H, which are the reaction intermediates of the dehydrogenation of formic acid, upon irradiation with a pulse with a carrier frequency equal to the plasmon resonance of a (not included) Au nanorod. We simulate the electron/hole dynamics at frozen nuclei by propagating the time-dependent Schrödinger equation in the space of time-dependent density-functional-theory pseudo-eigenstates in the tight-binding approximation. We have taken into account a cluster with two layers of Pd and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mn>3</mml:mn> <mml:mo>×</mml:mo> <mml:mn>3</mml:mn></mml:mrow> <mml:annotation>$$ 3\times 3 $$</mml:annotation></mml:semantics> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mn>4</mml:mn> <mml:mo>×</mml:mo> <mml:mn>4</mml:mn></mml:mrow> <mml:annotation>$$ 4\times 4 $$</mml:annotation></mml:semantics> </mml:math> atoms per layer (2L3 and 2L4, respectively) or with three layers and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mn>3</mml:mn> <mml:mo>×</mml:mo> <mml:mn>3</mml:mn></mml:mrow> <mml:annotation>$$ 3\times 3 $$</mml:annotation></mml:semantics> </mml:math> atoms per layer (3L3). For all the systems, a net negative charge on HCOO has been found, according to a photoinduced direct charge-transfer mechanism. For 3L3, an indirect charge-transfer mechanism, occurring after 50 fs and inducing a hole injection into HCOO, has also been found. Moreover, we also used a tailored pulse to populate the antibonding molecular orbital localized on the C-H bond for 3L3.