Extensive work performed to make PEFC as a viable industrial product have had solved most of PEFC issues but left two that have been creating hurdles in its commercialization; cost and a lifetime. Unfortunately, both these issues have a strong correlation, i.e., increasing platinum amount increases the lifetime while at same time hikes the cost. Over the time, it is reported that alloys of Pt are unstable under fuel cell reaction conditions. In sharp contrast to bulk and nano-size alloys, the researchers find that the orderly prepared sub-nanometer size Pt-alloys demonstrate exceptionally durability. We have applied the high-level DFT calculations to understand the exceptional durability of these alloys and design the methodology for fast screening of the most stable Pt-sub-nm size alloys. Our bonding analysis for all possible homotopic isomers showed that the stability of orderly prepared small clusters equally depends on both composition and arrangement of atoms within the clusters and the direct relation was found between the stability of bimetallic alloys and number of bonds present in the clusters and vice versa. Moreover, for screening the most stable isomers, we report a general and robust strategy.