Conversion of water and carbon dioxide into methanol with solar energy on Au/Co nanostructured surfaces

Abstract

Conversion of carbon dioxide (CO 2 ) and water (H 2 O) to methanol (CH 3 OH) is achieved through an artificial photosynthesis procedure utilizing cobalt (Co) micro-particle based photocatalyst and solar energy in a simple, closed reactor. The photocatalyst is fabricated by exposing the surfaces of cobalt microparticles to femtosecond laser irradiation in a gold chloride (AuCl) solution. The morphology and composite of the photocatalyst surfaces were observed and detected to be a layer of cobalt dioxide (CoO) nano-flakes on which some gold (Au) nanoparticles were deposited. The Au nanoparticles harvest the Sunlight energy through a plasmonic effect. The energy absorbed by Au nanoparticles creates electrons and holes which excite the H 2 O and CO 2 molecules adsorbed on CoO nanostructure surfaces to form excited hydrogen (H 2 ) * and excited carbon monoxide (CO) * on the CoO surface. The excited molecules combine to form CH 3 OH on the CoO surface. The Au/CoO/Co nanostructured surfaces are useful for developing a low-cost method to convert solar energy to chemical energy in the form of methanol.

Temperature Dependence of the Artificial Photosynthesis Reactions Catalyzed by Nanostructured Co/CoO

“…The enhanced photons dissociate the CO 2 and water molecules, and the dissociated molecules synthesize hydrocarbons on the Co/CoO surfaces. ,,, The lowest unoccupied molecular orbital (LUMO) of the adsorbed CO 2 has been found to be near to the bottom of the conduction band of CoO, which plays an important role in the dissociation of CO 2 . The carbon isotope effects in the artificial photosynthesis reactions catalyzed by a nanostructured Co/CoO support that when sunlight irradiates the nanostructured surface, electrons may be excited from a defect energy level to the conduction band of CoO and then quantum mechanically tunnel to the LUMO of the CO 2 molecules through the plasmonic nano-focusing at the interface. − On the other hand, the plasmon-induced hot electrons in Co may also inject into the conduction band of CoO and then quantum mechanically tunnel to the LUMO energy levels of CO 2 molecules. − Then, CO 2 molecules become charged molecules (CO 2 ) − , which are not stable. An electron is excited from the valence band of CoO to the CoO defect states , that are above the valence band on top of CoO.…”

“… 3 − 5 Then, CO 2 molecules become charged molecules (CO 2 ) − , which are not stable. An electron is excited from the valence band of CoO to the CoO defect states 3 , 4 that are above the valence band on top of CoO. The generated hole in the valence band of CoO then transfers to the highest occupied molecular orbital (HOMO) of the adsorbed H 2 O molecules that are on the surface of CoO, which results in (H 2 O) + .…”

“…The carbon isotope effects in the artificial photosynthesis reactions catalyzed by a nanostructured Co/CoO support that when sunlight irradiates the nanostructured surface, electrons may be excited from a defect energy level to the conduction band of CoO and then quantum mechanically tunnel to the LUMO of the CO 2 molecules through the plasmonic nano-focusing at the interface. − On the other hand, the plasmon-induced hot electrons in Co may also inject into the conduction band of CoO and then quantum mechanically tunnel to the LUMO energy levels of CO 2 molecules. − Then, CO 2 molecules become charged molecules (CO 2 ) − , which are not stable. An electron is excited from the valence band of CoO to the CoO defect states , that are above the valence band on top of CoO. The generated hole in the valence band of CoO then transfers to the highest occupied molecular orbital (HOMO) of the adsorbed H 2 O molecules that are on the surface of CoO, which results in (H 2 O) + . − Since the excited (CO 2 ) − and (H 2 O) + molecules are unstable, they synthesize chain hydrocarbons (C n H 2 n +2 , where 3 ≤ n ≤ 16) on the CoO catalyst surfaces. − The excited (CO 2 ) − and (H 2 O) + molecules may also further dissociate to form CO and H 2 .…”

“…An electron is excited from the valence band of CoO to the CoO defect states , that are above the valence band on top of CoO. The generated hole in the valence band of CoO then transfers to the highest occupied molecular orbital (HOMO) of the adsorbed H 2 O molecules that are on the surface of CoO, which results in (H 2 O) + . − Since the excited (CO 2 ) − and (H 2 O) + molecules are unstable, they synthesize chain hydrocarbons (C n H 2 n +2 , where 3 ≤ n ≤ 16) on the CoO catalyst surfaces. − The excited (CO 2 ) − and (H 2 O) + molecules may also further dissociate to form CO and H 2 .…”

Study the plasmonic property of gold nanorods highly above damage threshold via single-pulse spectral hole-burning experiments

“…Gold nanorods attract our attention due to their applications in medicine, chemistry and physics, including biosensing 1 , drug delivery 2 , cellular imaging 3 , 4 , cancer therapy 5 , chemical analysis 6 , 7 , catalysts 8 – 12 , electronics 13 , 14 and nonlinear processes 15 . These applications utilize the plasmonic effect: the interaction of conductive electrons in the metallic structures with electromagnetic fields 16 .…”