The highly selective conversion of nitrite to N-2 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 N-2: defects of any symmetry dramatically reduce the N-2 evolution at [(100) x (110)] and [(100) x (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 NH2,(ads) which in a certain potential window combines with NOads to give N-2 in a Langmuir-Hinshelwood reaction. Our findings are similar to those for other processes generating N-2, 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 N-2. The advantages of this pathway over other N-2-generating pathways are pointed out.