Correlating the crystal structure and facet of indium oxides with their activities for CO electroreduction.

Constructing structure-function relationships is critical for the rational design and development of efficient catalysts for CO electroreduction reaction (CORR). InO is well-known for its specific ability to produce formic acid. However, how the crystal phase and surface affect the CORR activity is still unclear, making it difficult to further improve the intrinsic activity and screen for the most active structure. In this work, cubic and hexagonal InO with different stable surfaces ((111) and (110) for cubic, (120) and (104) for hexagonal) are investigated for CORR. Theoretical results demonstrate that the adsorption of reactants on cubic InO is stronger than that on hexagonal InO, with the cubic (111) surface being the most active for CORR. In experiments, synthesized cubic InO nanosheets with predominantly exposed (111) surfaces exhibited a high HCOO Faradaic efficiency (87.5%) and HCOO current density (-16.7 mA cm) at -0.9 V vs RHE. In addition, an aqueous Zn-CO battery based on a cubic InO cathode was assembled. Our work correlates the phases and surfaces with the CORR activity, and provides a fundamental understanding of the structure-function relationship of InO, thereby contributing to further improvements in its CORR activity. Moreover, the results provide a principle for the directional preparation of materials with optimal phases and surfaces for efficient electrocatalysis.