Dense Niobium Oxide Coating on Carbon Black as a Support to Platinum Electrocatalyst for Oxygen Reduction

Abstract

Carbon black (CB) is commonly used to support Pt as an electrocatalyst in fuel cells. However, it is easily corroded in electrochemical reactions, such as in the oxygen reduction reaction (ORR), leading to catalyst degradation. In this paper, we report results of protecting the CB using an ultrathin 5 nm film of niobium oxide conformally coated on the CB using a new coating technique. Electrochemical test in ORR shows only a 1.7 % activity loss after 5000 cycles, demonstrating an excellent durability of the electrocatalyst. Compared to the electrocatalyst without niobium oxide coating, it shows a 25 mV improvement in half-wave potentials, indicative of a better kinetics. A positive shift in binding energy was found in Pt 4 f, implying electron delocalization has occurred when Pt is interfaced with the niobium oxide support. The activity enhancement is attributed to the electronic structure change in the electrocatalyst as a result of metal-support interactions.

Nanoscopic Silicon Oxide Overlayers Improve the Performance of Ruthenium Oxide Electrocatalysts Toward the Oxygen Evolution Reaction

“…64 Since the STEM-EDS of SiO x |RuO 2 showed the SiO x formed a thicker 3-7 nm coating on the bare GC surface, it is plausible that the additional mass transfer resistance imparted by the SiO x overlayer could partially protect the GC surface from oxidation. This hypothesis is also in agreement with literature on oxide coatings such as Nb 2 O 5 , 24 binary SnO x with TiO 2 25 or SiO 2 26 that have been implemented to prevent carbon corrosion during the oxygen reduction reaction at Pt-based catalysts. This result has implications for PEM electrolyzers and fuel cells, for which oxidation of the titanium-or carbon-based substrates used at the anode has been identified as a failure mode.…”

“…Similar to DSAs, OECs can also enhance stability, and can do so by multiple mechanisms. 23 Oxide coatings such as Nb 2 O 5 , 24 binary SnO x with TiO 2 , 25 or SiO 2 26 have been implemented to z E-mail: de2300@columbia.edu prevent carbon corrosion during the oxygen reduction reaction at Ptbased catalysts. In this way, the OEC architecture is advantageous relative to DSAs for which substrate corrosion can cause degradation.…”

Highly Active Lanthanum Perovskite Electrocatalysts (LaMnxCo1-xO3 (0 ≤ x ≤ 1)) by Tuning the Mn:Co Ratio for ORR and MOR in Alkaline Medium

“…The two main parameters that govern the quality of oxygen transfer on the surface of the catalyst are mass activity and kinetic current density. The mass activity measured for LaMn 0.4 Co 0.6 O 3 at 0.9 V was found to be highest at 23.2 mAmg −1 that is very close to the commercial Pt/C reported elsewhere [54]. The kinetic current density was calculated based on Eq.…”

Enhancement of the Oxygen Reduction Reaction Activity of Pt by Tuning Its d-Band Center via Transition Metal Oxide Support Interactions

“…It was thus considered that the peak shift for Pt 4f cannot be an index for making a connection between the electronic state of Pt NPs and the ORR activity. However, there are many studies reporting that TiO x , NbO x , and Ti x Nb y O z support materials accelerate the ORR. − The peak shift of the Pt 4f peak of Pt NPs deposited on Nb-doped TiO 2 supports, which is caused by the donation of electrons from the support material to Pt NPs, has also been reported . X-ray absorption near-edge structure (XANES) spectra have been also used to evaluate the Pt d -band vacancy .…”