Towards a better Sn: efficient electrocatalytic reduction of CO₂ to formate by Sn/SnS₂ derived from SnS₂ nanosheets

Electrocatalytic reduction of CO₂ into liquid fuels using electricity from renewable sources has been attracting considerable interest because of the present energy and environmental crisis. However, current electrocatalysts for this reaction generally suffer from either high cost for noble metal based catalysts or low energetic efficiency and poor product selectivity for other transition metal or carbon based materials. In this paper, we report a catalyst based on two–dimensional SnS₂ nanosheets supported on reduced graphene oxide (SnS₂/rGO) synthesized by a “one–pot” hydrothermal reaction for electrocatalytic reduction of CO₂ into formate with high activity, selectivity and durability. The catalyst is capable of producing formate at an overpotential as low as 0.23 V and reaches a maximum faradaic efficiency of 84.5% and the current density of 13.9 mA cm^–2 at an overpotential of 0.68 V in aqueous bicarbonate medium. Microscopic, spectroscopic and electrochemical characterizations reveal that the electrocatalytic activity towards CO₂ reduction arises from the presence of reduced metallic tin formed from SnS₂ under cathodic electrolysis conditions; the enhanced performance is attributed to the residual SnS₂. This sulfide–derived metal catalyst with enhanced performance may open a perspective on a new promising class of materials for electrocatalytic reduction of CO₂.