Triple-Phase Interface Engineering over an In 2 O 3 Electrode to Boost Carbon Dioxide Electroreduction.

The electrocatalytic reduction of CO 2 is deemed to be a promising method to ease environmental and energy issues. However, achieving high efficiency and selectivity of CO 2 electroreduction remains a bottleneck due to huge limitation of CO 2 mass transfer and competition of hydrogen evolution reaction (HER) in aqueous solution. In this work, we propose to utilize triple-phase interface engineering over an In 2 O 3 electrode to enhance its CO 2 reduction reaction (CO 2 RR) performance. Notably, distinguishing from other research studies (doping, defect introduction, and heterojunction construction) that regulate the nature of In 2 O 3 -based catalysts themselves, we herein tune interfacial wettability of In 2 O 3 using facile fluoropolymer coating for the first time. In contrast to the hydrophilic In 2 O 3 electrode [Faraday efficiency (FE) HCOOH ∼ 62.7% and FE H2 ∼ 24.1% at -0.67 V versus RHE], the hydrophobic fluoropolymer (taking polyvinylidene fluoride as an example)-coated In 2 O 3 electrode delivers a significantly enhanced FE HCOOH of 82.3% and a decreased FE H2 of 5.7% at the same potential. Upon combining contact angle measurements, density functional theory calculation, and ab initio molecular dynamics simulation, the enhanced CO 2 RR performance is revealed to be attributed to the rich triple-phase interfaces formed after fluoropolymer coating as an "aerophilic sponge", which increases the local concentration of CO 2 near In 2 O 3 active sites to improve CO 2 reduction and meanwhile reduces the accessible water molecules to suppress competitive HER. This work presents a feasible approach for the enhanced selectivity of HCOOH yield over In 2 O 3 by triple-phase interface engineering, which also provides a convenient and effective method for developing other materials used in gas-consumption reactions.