Electrosynthesis of Co/PPy nanocomposites for ORR electrocatalysis: a study based on quasi-in situ X-ray absorption, fluorescence and in situ Raman spectroscopy

Coelectrodeposition of Ternary Mn-Oxide/Polypyrrole Composites for ORR Electrocatalysts: A Study Based on Micro-X-ray Absorption Spectroscopy and X-ray Fluorescence Mapping

“…The stabilization of higher-valent Mn by doping with two-valent cations is expected on the basis of [53,54] and results to be more effective in the case of co-doping in ternary systems rather than by simple doping with a single species; moreover, galvanic coupling provided by Cu 0 turns out to be even more effective in stabilizing the 4-valent form [55]. forms, coherently with our results on Co/PPy [15,42] and Mn-Co/PPy [40]. The presence of both valences results from the fact that this element is incorporated into the composite by both electrodeposition and electroprecipitation processes taking place during the cathodic and anodic pulse-plating branches, respectively.…”

“…The electrodeposition protocol was a modification of the step pulsed potential method originally proposed in [37] and revised in [15,44], consisting in an initial step at 0 V for 1 s (#1), a subsequent anodic pulse at +1.2 V for 0.5 s (#2), a cathodic step at −1.8 V for 0.5 s (#3) and a final anodic step at +1.2 V for 0.2 s (#4). The potential values have been selected according to the approach discussed in [40,41].…”

“…The former case corresponds generally to the growth of oxides of potential functional interest, e.g., in catalysis [13,15] or corrosion protection, the latter instead to the redissolution of the metal or to the formation of inactive solid species such as hydroxides or basic salts.…”

“…It is the authors' opinion that it is currently difficult to gain a general understanding and consequently of controlling the characteristics of the composites, especially in terms of composition, chemical state, number, size, and spatial distribution of the electrodeposited metal crystals. We therefore reckon that the systematic use of complementary multitechnique ex situ [41], quasi in situ [15] and in situ [42] microspectroscopic tools is required for next generation studies of these systems.…”

“…ORR in alkaline media is a fundamental cathodic reaction in polymer membrane electrolyte fuel cells and metal-air batteries [43]. Among the different materials proposed, a highly attractive class of electrocatalysts is the non-precious metal/polypyrrole system (e.g., [15,41,42,44,45] and references therein). Polypyrrole is an excellent matrix for ORR catalysts for several reasons: (i) its relatively high nitrogen content, that allows the formation of ORR active Me-N sites within the intact polymer structure; (ii) reasonable environmental stability and relatively good robustness with respect to peroxide attack; (iii) high electrical conductivity [46]; (iv) optimal adhesion of catalyitic oxides [47].…”