How Light-Harvesting Semiconductors Can Alter the Bias of Reversible Electrocatalysts in Favor of H2 Production and CO2 Reduction

• Published in: Journal of the American Chemical Society 2013-10, Vol.135 (40), p.15026-15032
• Main Authors: Bachmeier, Andreas, Wang, Vincent C. C, Woolerton, Thomas W, Bell, Sophie, Fontecilla-Camps, Juan C, Can, Mehmet, Ragsdale, Stephen W, Chaudhary, Yatendra S, Armstrong, Fraser A
• Format: Article
• Language: English
• Subjects: Aldehyde Oxidoreductases - chemistry; Aldehyde Oxidoreductases - metabolism; Bias; Biomimetics - instrumentation; Biomimetics - methods; Carbon dioxide; Carbon Dioxide - chemistry; Catalysis; Catalysts; Electrocatalysts; Electrochemistry; Electrodes; Enzymes; Hydrogen - chemistry; Hydrogenase - chemistry; Hydrogenase - metabolism; Light; Models, Molecular; Multienzyme Complexes - chemistry; Multienzyme Complexes - metabolism; Oxidation-Reduction; Photosynthesis; Protein Conformation; Reduction; Semiconductors; Titanium dioxide
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja4042675

The most efficient catalysts for solar fuel production should operate close to reversible potentials, yet possess a bias for the fuel-forming direction. Protein film electrochemical studies of Ni-containing carbon monoxide dehydrogenase and [NiFeSe]-hydrogenase, each a reversible electrocatalyst, show that the electronic state of the electrode strongly biases the direction of electrocatalysis of CO2/CO and H+/H2 interconversions. Attached to graphite electrodes, these enzymes show high activities for both oxidation and reduction, but there is a marked shift in bias, in favor of CO2 or H+ reduction, when the respective enzymes are attached instead to n-type semiconductor electrodes constructed from CdS and TiO2 nanoparticles. This catalytic rectification effect can arise for a reversible electrocatalyst attached to a semiconductor electrode if the electrode transforms between semiconductor- and metallic-like behavior across the same narrow potential range (