A new tin-based active and low-cost catalyst for hydrogen fuel cell technology Although platinum and platinum alloys RESULTS have long been the only feasible catalysts This breakthrough study reports the discovery of the the first to speed up electrochemical reactions in p-block single metal site catalyst, Sn-N-C, exhibiting a catalytic hydrogen fuel cells, the use of non-precious ORR activity in acidic environments that meets and exceeds all state-of-art non-PGM catalysts. The catalyst’s synthesis metal alternatives is becoming possible as a consists in the pyrolysis of a catalyst precursor prepared from consequence of performance improvements polyaniline and anhydrous Sn(II)Cl , followed by multiple acid2 and better understanding of the structural leaching steps. The SnNC-NH catalyst obtained by activation3 of Sn-N-C with NH exceeds the state-of-the-art FeNC-NH3 3 and mechanistic basis of their activity. X-ray catalyst by 40-50% in terms of measured current density at absorption spectroscopy, in combination with cell voltages lower than 0.7 V (Figure 1). other characterisation methods, enabled us FIGURE 1 shedding light on the detailed active sites’ structure of a novel Sn-based electrocatalyst, exhibiting an oxygen reduction reaction catalytic activity that meets and exceeds all state-of-art non-precious materials. This opens new catalyst chemistries to replace platinum. The transition toward renewable energies appears a necessary process to face the increasing energy demand but also to reduce our environmental impact, in particular global greenhouse effect, and our dependency on fossil fuels. Polymer-electrolyte- membrane fuel cells (PEMFC) are envisioned as a power source for electric vehicles offering the advantage of a compact and low weight device that operates at low temperatures, with a high-energy conversion efficiency (more than 60% operating with direct hydrogen) and almost zero emissions.[1] The Sn K-edge EXAFS fitting identified the ex situ local structure Developing non-precious, platinum group metal (PGM)-free of the Sn-based active site (Figure 2a). Specifically, we found catalysts as a replacement of Pt and Pt alloys for the sluggish that the vast majority of Sn atoms are atomically dispersed, and oxygen reduction reaction (ORR) is crucial for the commercial they are covalently coordinated by 4 in-plane nitrogen (and/or success of these environmentally-friendly energy conversion carbon) atoms at 2.06 Å, involving also 1 oxygen adsorbed devices. The last 50 years of research on PGM-free catalysts ligand above the plane at 2.13 Å. The EXAFS analysis finds a identified Metal-N macrocycles and then Metal-N moieties minor Sn-Sn contribution corresponding to a bond distance anchored in a conductive carbon matrix as a potentially lower-4 X of 3.28 Å, which is consistent with the presence of nanosized cost alternative. Tremendous research efforts mainly focused SnO. The possible coexistence of Sn(II) and Sn(IV) species2 on Fe-based and Co-based catalysts of the type Metal-N-C, was also revealed by the threshold energy position of the Sn produced by high temperature pyrolysis of a metal precursor, K-edge XANES spectrum, placed between that of the XANES a nitrogen precursor, and a carbon support or precursor.[2-4] spectra for SnO and SnO (Figure 2b). These findings agree2 The challenge of finding sufficiently active and durable non-PGM with Sn(II) and Sn(IV) oxidation states identified by XPS and by catalysts is however still ahead. Mössbauer components, unambiguously assigned to Sn(II) and 38