Efficient and Selective Interplay Revealed: CO₂ Reduction to CO over ZrO₂ by Light with Further Reduction to Methane over Ni⁰ by Heat Converted from Light

Abstract

Abstract The reaction mechanism of CO 2 photoreduction into methane was elucidated by time‐course monitoring of the mass chromatogram, in situ FTIR spectroscopy, and in situ extended X‐ray absorption fine structure (EXAFS). Under 13 CO 2 , H 2 , and UV/Vis light, 13 CH 4 was formed at a rate of 0.98 mmol h −1 g cat −1 using Ni (10 wt %)‐ZrO 2 that was effective at 96 kPa. Under UV/Vis light irradiation, the 13 CO 2 exchange reaction and FTIR identified physisorbed/chemisorbed bicarbonate and the reduction because of charge separation in/on ZrO 2 , followed by the transfer of formate and CO onto the Ni surface. EXAFS confirmed exclusive presence of Ni 0 sites. Then, FTIR spectroscopy detected methyl species on Ni 0 , which was reversibly heated to 394 K owing to the heat converted from light. With D 2 O and H 2 , the H/D ratio in the formed methane agreed with reactant H/D ratio. This study paves the way for using first row transition metals for solar fuel generation using only UV/Vis light.