Light Driven Catalytic CO2 Reduction: Lessons Learnt when Low is Actually No Activity

Abstract

When initial testing of complexes as CO2RR catalysts under homogeneous photocatalytic conditions leads to modest formation of CO, H2 and even formate, as is the case herein, one can be tempted to conclude that the complexes are somewhat active catalysts. But ultimately the activity observed may instead have arisen from some of the many other components that are present in these tests: these many potential sources of apparent catalytic activity, which can dominate results in the case of low catalyst activity, are summarised herein, as they are seldom highlighted, yet great care must be taken with the choice and preparation of all the components to ensure that high quality test data is acquired, including on blanks and controls, so that incorrect interpretation of the results is avoided. We conclude that, despite initial appearances, the 5 copper(II) complexes tested herein have similar activity to the controls, so are not active CO2RR catalysts under the conditions studied.