Scheme 1.

Redox States^a Involved in Catalytic CO₂ Interconversion at the Active Site of CODH and How p-Type and n-Type Semiconductors Rectify Catalytic Electron Flow

^aC_red1 and C_red2 are the catalytically active states that effect CO oxidation and CO₂ reduction, respectively. The transient C_int state participates in the half-cycle regeneration of these active states. The small-molecule inhibitors CN⁻ and NCO⁻ selectively intercept states C_red1 and C_red2 and inhibit CO oxidation (CN⁻) and CO₂ reduction (NCO⁻).¹⁴