A Robust Electrocatalyst for Oxygen Reduction Reaction Assembled with Pt Nanoclusters and a Melem‐Modified Carbon Support

Abstract

Highly active and stable cathode catalysts are crucial functional materials for high‐performance proton exchange membrane fuel cells. Herein, robust cathode catalysts for the oxygen reduction reaction (Pt/melem‐modified carbon (MMC)) that are assembled with Pt nanoclusters (NCs) and MMC supports are reported. The mass activity (MA) of a Pt/MMC catalyst reaches 907 mA mg−1 Pt, which is 3.9 and 4.2 times over a homemade Pt/C catalyst (Pt/VXC‐72R) and a commercial Pt/C catalyst with similar Pt particle sizes, respectively. After 10 000 voltage cycles from 1.0 to 1.5 V at 60 °C, the MA of Pt/MMC decreases by only 2% from the initial value, vastly superior to that of the Pt/C catalysts. Theoretical calculations and X‐ray absorption fine structure analysis results show that chemical bonds form between Pt nanoclusters and MMC. The adsorption energies of OOH* on the catalytic sites in Pt/MMC obviously increase, while those of OH−* decrease compared with those on Pt/C, which accounts for the measured high catalytic activity, providing a promising manner to overcome the specific scaling relations between the stability of adsorbed OH−* and OOH* on a given Pt surface. The high durability of Pt/MMC derives from strong chemical interactions between Pt NCs and the support MMC.

Metal Nanoclusters Synthesized in Alkaline Ethylene Glycol: Mechanism and Application

“…Unprotected metal nanoclusters provide tractable tools for experimentally studying the effects of individual factors such as the metal composition, size, support, and the surface modification groups on the catalytic properties of metal nanocluster catalysts by assembling structure-controllable catalysts with unprotected metal or alloy nanoclusters that act as the building blocks [ 21 , 45 , 112 , 113 , 114 , 115 ]. A theoretical calculation based on the experimental results could further deepen the understanding of the relationship between the structure and performance of the catalytic sites of metal nanocluster catalysts [ 55 , 116 ]. Based on the relevant experimental and theoretical research results described in this section, in this paper, we propose a principle of the influence of carriers, ligands and modifiers in metal nanocluster catalysts on the catalytic properties.…”

“…In a recent research [ 116 ], we synthesized two catalysts (Pt/MMC-6.8N and Pt/VXC-72R) with the same sized Pt nanoclusters and different supports by assembling the unprotected Pt nanoclusters with a mean diameter of 1.4 nm with a melem-modified carbon carrier containing 6.8 wt% of N (MMC-6.8 N) and a carbon carrier VXC-72R. These catalysts were used to catalyzed the oxygen reduction reaction (ORR), a crucial reaction in fuel cells.…”

“…The Bader charges of the Pt atoms at the marked adsorption sites for OOH* and OH − * on Pt/C with an average value of −0.049 |e| are less than that on Pt/MMC (with an average value of −0.077 |e|). Reproduced with permission, Copyright 2022 Wiley-VCH GmbH [ 116 ].…”

“… Plots of Bader charges of the representative adsorption site Pt atoms versus adsorption energies of OOH* on Pt 40 NCs of Pt 40 /C ( a ) and Pt 40 /MMC ( b ); plots of Bader charges of the representative adsorption site Pt atoms versus adsorption energies of OH − * on Pt 40 NCs of Pt 40 /C ( c ) and Pt 40 /MMC ( d ). Reproduced with permission, Copyright 2022 Wiley-VCH GmbH [ 116 ]. …”

Effect of AST Atmosphere on Pt/C Electrocatalyst Degradation

“…In recent years, various AST protocols have been developed and actively applied to assess the durability of the catalysts [20,21]. Essentially, they are divided into protocols aimed at studying the catalyst's durability at the UPL of about 1.0 V (RHE) [22][23][24] and the durability of the carbon support at the UPL of about 1.4-1.6 V (RHE) [25][26][27]. On the one hand, researchers use the AST protocol at the UPL of about 1.0 V (RHE) due to the correspondence of the potential window to the operation of PEMFCs, with the potential increase usually occurring when the device is started.…”