Repurposing a Bio-Inspired NiFe Hydrogenase Model for CO₂ Reduction with Selective Production of Methane as the Unique C-Based Product

Abstract

In the current environmental and economic context, there is an urgent need to develop catalytic systems to efficiently activate and transform abundant small molecules while demonstrating selectivity when multielectron processes are involved. This is especially true for catalytic production of CH4 from CO2, as a limited number of active photo- or electro-catalysts have been described to date. Herein, we report the unprecedented reactivity of a molecular electrocatalyst physiadsorbed on a graphite electrode: the bioinspired [LN2S2NiIIFeIICp(CO)]+ (LN2S2 = 2,2′-(2,2′-bipryridine-6,6′-diyl)bis(1,1′-diphenylethanethiolate) complex selectively and catalytically reduces CO2 in acidic aqueous solution to produce a mixture of CH4 and H2. Under optimized conditions, at pH 4, Faradaic yields of 12% and 66% for CH4 and H2 production (TOFCH4 = 214 s–1, TOFH2 ≈ 5.1 × 103 s–1) are measured, respectively. We demonstrate that this binuclear NiFe catalyst is stable for hours under controlled potential electrolysis conditions.