Ultrasensitive Plasmon-Enhanced Infrared Spectroelectrochemistry.

IR spectroelectrochemistry (EC-IR) is a cutting-edge operando method for exploring electrochemical reaction mechanisms. However, detection of interfacial molecules is challenged by the limited sensitivity of existing EC-IR platforms due to the lack of high-enhancement substrates. Here, we propose an innovative plasmon-enhanced infrared spectroelectrochemistry (EC-PEIRS) platform to overcome this sensitivity limitation. Plasmonic antennae with ultrahigh IR signal enhancement are electrically connected via monolayer graphene while preserving optical path integrity, serving as both the electrode and IR substrate. The [Fe(CN) 6 ] 3- /[Fe(CN) 6 ] 4- redox reaction and electrochemical CO 2 reduction reaction (CO 2 RR) are investigated on the EC-PEIRS platform with a remarkable signal enhancement. Notably, the enhanced IR signals enable a reconstruction of the electrochemical curve of the redox reactions and unveil the CO 2 RR mechanism. This study presents a promising technique for boosting the in-depth understanding of interfacial events across diverse applications.