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Fast CO2 hydration kinetics impair heterogeneous but improve enzymatic CO2 reduction catalysis

Year: 2022

Journal: Nat. Chem., Volume 14, APR, page 417

Authors: Cobb, Samuel J.; Badiani, Vivek M.; Dharani, Azim M.; Wagner, Andreas; Zacarias, Sonia; Oliveira, Ana Rita; Pereira, Ines A. C.; Reisner, Erwin

Organizations: European Research Council [682833]; Leverhulme Trust [P80336]; Engineering and Physical Sciences Research Council Graphene Centre for Doctoral Training [EP/L016087/1]; Winston Churchill Foundation of the United States; Fundacao para a Ciencia e Tecnologia (Portugal) [SFRH/BD/100314/2014, SFRH/BD/116515/2016, PTDC/BII-BBF/2050/2020, UIDB/04612/2020, UIDP/04612/2020]; EU [810856]; NIH [p41-GM103311]; OMV; Fundação para a Ciência e a Tecnologia [SFRH/BD/116515/2016, PTDC/BII-BBF/2050/2020, SFRH/BD/100314/2014] Funding Source: FCT

The performance of heterogeneous catalysts for electrocatalytic CO2 reduction suffers from unwanted side reactions and kinetic inefficiencies at the required large overpotential. However, immobilized CO2 reduction enzymes-such as formate dehydrogenase-can operate with high turnover and selectivity at a minimal overpotential and are therefore 'ideal' model catalysts. Here, through the co-immobilization of carbonic anhydrase, we study the effect of CO2 hydration on the local environment and performance of a range of disparate CO2 reduction systems from enzymatic (formate dehydrogenase) to heterogeneous systems. We show that the co-immobilization of carbonic anhydrase increases the kinetics of CO2 hydration at the electrode. This benefits enzymatic CO2 reduction-despite the decrease in CO2 concentration-due to a reduction in local pH change, whereas it is detrimental to heterogeneous catalysis (on Au) because the system is unable to suppress the H-2 evolution side reaction. Understanding the role of CO2 hydration kinetics within the local environment on the performance of electrocatalyst systems provides important insights for the development of next-generation synthetic CO2 reduction catalysts. Carbonic anhydrase enzymatically catalyses CO2 hydration, and its effect on enzymatic and heterogeneous CO2 reduction has now been studied. Through the co-immobilization of carbonic anhydrase, it has been shown that faster CO2 hydration kinetics are beneficial for enzymatic catalysis (using formate dehydrogenase) but detrimental for heterogeneous catalysts, such as gold.