Supplementary MaterialsSupplementary Information 41467_2019_9503_MOESM1_ESM. Mn-Co spinel cathode that may deliver better power, at high current densities, when compared to a Pt cathode. The charged power thickness from the cell employing the Mn-Co cathode gets to 1.1 W cm?2 in 2.5 A cm?2 in 60?oC. Furthermore, this catalyst outperforms Pt at low dampness. In-depth characterization reveals which the remarkable performance hails from synergistic results where in fact the Mn sites bind O2 as well as the Co sites activate H2O, in order to facilitate the proton-coupled electron transfer procedures. This electrocatalytic synergy is normally Marimastat distributor pivotal towards the high-rate air reduction, under drinking water depletion/low dampness circumstances particularly. Introduction The latest decade has observed tremendous improvement in both components advancements and catalysis research of alkaline polymer electrolyte gasoline cells (APEFCs)1C9. Analysis efforts have already been powered by the actual fact that polymeric alkaline electrolytes will not only simplify the cell framework and operation, but provide opportunities for employing non-precious metal catalysts10C14 also. Nevertheless, despite great initiatives, the final objective has continued to be elusive. Although some materials, such as for example nitrogen-doped carbon-based components15,16, have already been suggested to demonstrate Pt-comparable activity to the air reduction response (ORR) in alkaline mass media, their functionality is a lot less than that of Pt in APEFCs17 still,18, when operated in high current densities necessary in automotive applications specifically. The testing of fuel-cell electrocatalysts is normally completed using rotating drive electrode (RDE) voltammetry. Nevertheless, the RDE experimental circumstances will vary from CTNND1 those within a polymer electrolyte gasoline cell distinctly, where in fact the electrode is usually fed with humidified gas, and the catalyst surface is usually under a humid atmosphere rather than in contact with an aqueous answer19, as is the case under RDE conditions. Thus, it is not amazing that good-performing electrocatalysts in RDE assessments can often exhibit poor overall performance under fuel-cell operation. Here, we statement an unexpected finding that the Mn-Co spinel catalyst (denoted hereafter as MCS) exhibits activity that is inferior to that of Pt, for ORR in RDE assessments, but superior overall performance in APEFC assessments, in particular under low-humidity conditions. At 60?oC, the power density of APEFC employing such a MCS cathode reaches 1.1?W?cm2 at 100 relative humidity (RH%) and 0.92?W?cm?2 at 50 RH%, in comparison to 1?W?cm2 at 100 RH% and 0.67?W?cm?2 at 50 RH% for any Pt cathode. Through comprehensive characterizations, an unreported synergistic effect of the Marimastat distributor MCS surface is usually unraveled, where the Mn sites prefer O2 binding and the Co sites favor H2O activation. Such a mechanism is usually pivotal in APEFC cathode, where water is usually a reactant but usually depleted. Results Electrochemical and fuel-cell assessments Physique? 1a presents common RDE profiles for the ORR catalyzed by Pt and Marimastat distributor MCS in 1.0?M KOH solution. A negative shift of 50?mV in the half-wave potential clearly indicates that this ORR occurs at a lower rate on MCS than on Pt, and this trend does not switch with potential as evidenced in the Tafel plots (inset to Fig.?1a). Such an observation would usually lead to the conclusion that this MCS would not be a good choice as ORR electrocatalyst for APEFCs. However, the gas cell assessments tell a different, and most unexpected, story (Fig.?1b). An APEFC with a Pt-Ru anode and a Pt cathode, exhibiting a peak power density (PPD) of 1 1?W?cm?2, Marimastat distributor is a benchmark of current APEFC research20,21. Upon replacing the Pt cathode with our MCS cathode, the cell overall performance underwent a slight loss at low current densities, but, as the current density increased, it kept increasing in a steady fashion, reaching a higher PPD of 1 1.1?W?cm?2, a overall performance metric never previously achieved in APEFCs with a non-precious metal cathode catalyst to the best of our knowledge. The MCS cathode can even sustain a current density of 3.5?A?cm?2, pointing to its inherently high activity. Open in a separate windows Fig. 1 Comparison of Mn-Co spinel (MCS)?catalyst and commercial Pt catalyst. a Rotating disk electrode (RDE) measurements in O2-saturated KOH answer (1?mol?L?1) using 40 wt% Pt/C (Johnson Matthey, 50?gPt?cm?2) and 40 wt% MCS/C (72 gmetal cm?2), respectively. Inset: Tafel plots. Scan rate = 5 mV s?1. Rotation rate = 1600 rpm. Observe Supplementary Figs?1 and 2 for relevant electrochemical data. b,?c Alkaline polymer electrolyte gas cell (APEFC) assessments with H2 and O2 at different relative humidities (RH). Anode catalyst: 60 wt%.