Efficient and Selective Interplay Revealed: CO Reduction to CO over ZrO by Light with Further Reduction to Methane over Ni by Heat Converted from Light.

The reaction mechanism of CO 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 CO , H , and UV/Vis light, CH was formed at a rate of 0.98 mmol h  g using Ni (10 wt %)-ZrO that was effective at 96 kPa. Under UV/Vis light irradiation, the CO exchange reaction and FTIR identified physisorbed/chemisorbed bicarbonate and the reduction because of charge separation in/on ZrO , followed by the transfer of formate and CO onto the Ni surface. EXAFS confirmed exclusive presence of Ni sites. Then, FTIR spectroscopy detected methyl species on Ni , which was reversibly heated to 394 K owing to the heat converted from light. With D O and H , 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.