Depleting fossil fuel sources and ever increasing demands for sustainable energies have encouraged us to develop suitable catalyst for hydrogen evolution reaction (HER), being H2 a potential eco-viable energy vector. In nature, H+ + e- ? � H2? interconversion is catalysed by a enzyme called hydrogenase (e. g. - Ni-Fe & Fe-Fe hydrogenase based on central atoms present at the active site) under mild conditions. We have synthesized A & B, two different synthetic analogues with Fe2S2 core and baring pendant azadithiolate moiety, relevant to Fe-Fe hydrogenase active site. The electrocatalytic HER efficiencies of these complexes in acidic media under heterogeneous condition is investigated and it has proved to be as high as the natural systems (TOFFe-Fe hydrogenase = 100- 10000 s-1; TOFA = 6300 s-1 & TOFB = 7500 s-1 in 0.5 M H2SO4) with only moderate overpotentials. The instability of these complexes in oxic catalytic conditions leads us to investigate the electrocatalytic oxygen reduction reaction (ORR) by these complexes. This shows formation of 55 � 7 % reactive partially reduced oxygen species (PROS) irrespective of the bridgehead atom at pendant dithiolate moiety. Such high amount of PROS is responsible the degradation of the binuclear cluster as described for the natural hydrogenase as well. The formation of the amount of PROS is diminished as the pH is lowered. The extent of lowering of the PROS is greater for the nitrogen atom present at the bridgehead position and reached to 21% for N-Me group at the bridgehead and show rather high efficiency for HER Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/241nm/uploads/69187_4a_ton_e_4a.jpg' alt='' /> .

Electrocatalytic H2 generation by synthetic Fe-Fe hydrogenase mimics in water and their oxygen reactivities

248th National Meeting (2014)

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