Dual-Site Cascade Oxygen Reduction Mechanism on SnO_x/Pt–Cu–Ni for Promoting Reaction Kinetics

Abstract

Designing highly active oxygen reduction reaction (ORR) catalysts is crucial to boost the fuel cell economy. Previous research has mainly focused on Ptbased alloy catalysts in which surface Pt is the solely active site and the activity improvement was challenged by the discovered scaling relationship. Herein we report a new concept of utilizing dual active sites for the ORR and demonstrate its effectiveness by synthesizing a SnO x /Pt− Cu−Ni heterojunctioned catalyst. A maximum of 40% enhancement in the apparent specific activity, which corresponds to 10-fold enhancement on interface sites, is measured compared with pure Pt−Cu−Ni. Detailed investigations suggest an altered dual-site cascade mechanism wherein the first two steps occur on SnO x sites and the remaining steps occur on adjacent Pt sites, allowing a significant decrease in the energy barrier. This study with the suggested dual-site cascade mechanism shows the potential to overcome the ORR energy barrier bottleneck to develop highly active catalysts.

Strategies to Break the Scaling Relation toward Enhanced Oxygen Electrocatalysis

“…89 Shen et al reported the design of dual adsorption sites by synthesizing SnO x /Pt-Cu-Ni composites to circumvent the scaling relation between *OOH and *OH on the same adsorption site and promote the catalytic activity ( Figure 5). 90 Theoretical studies demonstrated a dual-site cascade mechanism, in which the first two steps take place on a SnO x site (*OOH formation is a potential-determining step with the lowered barrier of 0.…”

Dopants in the Design of Noble Metal Nanoparticle Electrocatalysts and their Effect on Surface Energy and Coordination Chemistry at the Nanocrystal Surface

“…Reproduced with permission. [56] Copyright 2019, American Chemical Society. f) The mechanism for the OER in acidic electrolytes: AEM and LOM.…”

“…[47b,56] For instance, SnO x on PtCuNi could be an active site for the first two ORR reactions, whereas the remaining steps took place at Pt-enriched surface of PtCuNi (Figure 6d,e). [56] Figure 6d As with the ORR, the binding strength of the reaction intermediates could affect the OER activity, making band shift an essential factor to explain the catalytic performance of the transition metal and alloy catalysts. [10a] For example, incorporation of Co and Ni into Ir weakens the binding of the oxygen intermediates in the RDS, lowering the d-band center of Ir (from −3.89 to −4.09 eV).…”

“…e) Schematic illustration of dual roles during the ORR process of SnO x /Pt-Cu-Ni. Reproduced with permission [56]. Copyright 2019, American Chemical Society.…”

SnO x @β–SnO heterostructures and their enhanced photocurrent in photoelectrochemical cell

“…For example, Sn 3 O 4 /SnO 2 heterostructures were used as gas sensor [3], SnO/Sn 3 O 4 heterostructures were used as photocatalyst [4]. And SnO x composites were used as active oxygen reduction reaction (ORR) catalysts to promote reaction kinetics [5]. And SnO/SnO 2 heterojunctions assembled from ultrathin nanosheets showed improved properties of gas sensors [6][7][8].…”