Abstract
Imparting an enhanced CO2 reduction selectivity to ZnGa2O4 photocatalysts has been demonstrated by controlled crystallization from interdispersed nanoparticles of zinc and gallium hydroxides. The hydroxide precursor in which Zn(ii) and Ga(iii) are homogeneously interdispersed was prepared through an epoxide-driven sol–gel reaction. ZnGa2O4 obtained by a heat-treatment exhibits a higher surface basicity and an enhanced affinity for CO2 molecules than previously-reported standard ZnGa2O4. The enhanced affinity for CO2 molecules of the resultant ZnGa2O4 leads to highly-selective CO evolution in CO2 photo-reduction with H2O reductants. The present scheme is promising to achieve desirable surface chemistry on metal oxide photocatalysts.
Highlights
Heterogeneous catalysis for environmental-friendly production of resources has attracted remarkable attention.[1]
Ag co-catalyst, that is required to maximize the reaction selectivity toward CO evolution, can be decreased into 5% of the previous reports, thanks to the high affinity for CO2 adsorption of the resultant ZnGa2O4 surface. Based on these insights obtained in this representative ZnGa2O4 system, synthesis of complex oxide catalysts through the crystallization of interdispersed hydroxides NPs is expected to be applied to design a wide range of complex oxide catalysts with an intended surface
Two small peaks are assigned to 003 and 006 diffraction peaks of Zn–Ga layered double hydroxide (LDH) crystal,[29] whose Zn2+/Ga3+ ratio was estimated as 1.5 from TEMEDS mapping shown in Fig. S1.† By Bragg's law using the diffraction peak at 2q 1⁄4 9.9, the interlayer separation is calculated to be 0.89 nm, which corresponds to an interlayer space of LDH accommodating nitrate anions.[30,31]
Summary
Heterogeneous catalysis for environmental-friendly production of resources has attracted remarkable attention.[1]. Surface analyses con rm that ZnGa2O4 prepared in the present scheme exhibits a higher base strength and a higher affinity for CO2 compared to those of standard ZnGa2O4 obtained by a solid phase reaction from a mixture of metal oxide precursors.
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