Towards a better Sn: Efficient electrocatalytic reduction of CO 2 to formate by Sn/SnS 2 derived from SnS 2 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.