Regulating the hydrophobic microenvironment of SnS2 to facilitate the interfacial CO2/H2O ratio towards pH-universal electrocatalytic CO2 reduction†

Electrocatalytic CO₂ reduction to formic acid is a promising strategy to obtain value-added chemicals and achieve the carbon cycle. However, its practical application is generally impeded by the limited accessibility of CO₂ to the catalyst's surface and the lack of an efficient universal catalyst across different pH levels. Herein, we report a new catalyst, i.e., SnS₂ decorated with a hydrophobic polymer polyvinylidene fluoride (SnS₂ + PVDF), for the effective electrocatalytic CO₂ reduction to formate/formic acid across a wide pH range in a flow cell. This catalytic system accomplishes a remarkable faradaic efficiency for the formic acid production in alkaline (98%), neutral (86%), and acidic (93%) electrolytes. Also, the single-pass carbon efficiency reaches up to 72.77% in acidic electrolytes. Water contact angle measurements in association with in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy results indicate that the inclusion of PVDF creates a hydrophobic microenvironment which increases the CO₂/H₂O ratio near the surface of SnS₂ particles. As a consequence, SnS₂ particles enjoy the enhanced CO₂ concentration around their surface to form many three-phase (solid–liquid–gas) boundaries. In situ Raman spectra combined with electrocatalytic studies reveal that SnS₂ undergoes reconstitution to form catalytically active Sn/SnS₂ during the reaction. These findings ensure and expand the generality of a hydrophobic microenvironment regulation strategy in promoting electrocatalytic CO₂ reduction to formic acid.