Selective Catalytic Reduction at Quasi-Perfect Pt(100) Domains: A Universal Low-Temperature Pathway from Nitrite to N2

Abstract

The highly selective conversion of nitrite to N₂ at a quasi-perfect Pt(100) electrode in alkaline media was investigated with a particular emphasis on its structure sensitivity and its mechanism. High-quality (100) terraces are required to optimize the catalytic activity and steer the selectivity to N₂: defects of any symmetry dramatically reduce the N₂ evolution at [(100) × (110)] and [(100) × (111)] surfaces. On the other hand, nitrite reduction proves to be an additional example of the unique intrinsic ability of (100) surfaces to catalyze reactions involving bond breaking and successive bond formation. In the present case, (100) is able to reduce nitrite to NH_2,ads, which in a certain potential window combines with NO_ads to give N₂ in a Langmuir–Hinshelwood reaction. Our findings are similar to those for other processes generating N₂, from bacterial anoxic ammonia oxidation (“anammox”) to the high-temperature NO + NH₃ reaction at Pt(100) crystals under ultra-high-vacuum conditions, thus suggesting that the combination of these two nitrogen-containing species is a universal (low-temperature) pathway to N₂. The advantages of this pathway over other N₂-generating pathways are pointed out.