Photocatalytic Conversion of Diluted CO 2 into Tunable Syngas via Modulating Transition Metal Hydroxides.

The conversion of diluted CO 2 into tunable syngas via photocatalysis is critical for implementing CO 2 reduction practically, although the efficiency remains low. Herein, we report the use of graphene-modified transition metal hydroxides, namely, Ni X Co 1- X -GR, for the conversion of diluted CO 2 into syngas with adjustable CO/H 2 ratios, utilizing Ru dyes as photosensitizers. The Ni(OH) 2 -GR cocatalyst can generate 12526 μmol g -1 h -1 of CO and 844 μmol g -1 h -1 of H 2 , while the Co(OH) 2 -GR sample presents a generation rate of 2953 μmol g -1 h -1 for CO and 10027 μmol g -1 h -1 for H 2 . Notably, by simply altering the addition amounts of nickel and cobalt in the transition metal composite, the CO/H 2 ratios in syngas can be easily regulated from 18:1 to 1:4. Experimental characterization of composites and DFT calculations suggest that the differing adsorption affinities of CO 2 and H 2 O over Ni(OH) 2 -GR and Co(OH) 2 -GR play a significant role in determining the selectivity of CO and H 2 products, ultimately affecting the CO/H 2 ratios in syngas. Overall, these findings demonstrate the potential of graphene-modified transition metal hydroxides as efficient photocatalysts for CO 2 reduction and syngas production.