Enhanced Durability of Automotive Fuel Cells via Selectivity Implementation by Hydrogen Spillover on the Electrocatalyst Surface

Abstract

Startup and shutdown (SU/SD) events in automotive polymer electrolyte membrane fuel cells cause an unintended oxygen reduction reaction (ORR) due to the mixing of air in the anode, leading to instantaneous potential jumps and subsequent carbon corrosion in the cathode. Here, a selective electrocatalysis method for the hydrogen oxidation reaction (HOR) is presented as a promising approach for inhibiting the ORR and preventing cathodic corrosion during SU/SD events. Platinum (Pt) supported on titanium dioxide (TiO 2 ) demonstrated HOR-selective electrocatalysis, made possible by extreme variation in conductivity according to the hydrogen concentration in the atmosphere. Under hydrogenrich conditions, hydrogen spillover occurred and led to the formation of a conduction pathway on the Pt/TiO 2 surface, promoting the HOR. Under oxygen-rich conditions, the conductivity of the TiO 2 surface caused it to return to its original insulating nature, inhibiting the ORR. In an SU/SD simulation protocol test, the HOR-selective Pt/TiO 2 demonstrated three-times-higher durability in a membrane electrode assembly in comparison with a commercial Pt/C catalyst.

Interfacial Hydrogen Spillover on Pd-TiO2 with Oxygen Vacancies Promotes Formate Electrooxidation

“…Despite these advances, the unitary regulation of the d-band center of Pd has not yet achieved satisfactory H ad desorption rates from Pd active sites. Recently, hydrogen spillover has provided new avenues for improving the H ad desorption rate of FOR catalysts with hydrogen-enriched Pd nanocrystals and hydrogen-deficient components, such as TiO 2 , SiO 2 , and WO 3 . − H ad migrates from the Pd surface to the surface of hydrogen-deficient components, simultaneously regenerating Pd active sites and enhancing H ad desorption. However, due to the low electronegativity of Pd, electrons tend to transfer from Pd to hydrogen-deficient components, resulting in an electron-deficient state of Pd .…”

Constructing highly durable reversal-tolerant anodes via integrating high-surface-area Ti4O7 supported Pt and Ir@IrOx for proton exchange membrane fuel cells

“…A similar outcome was observed in other titanium oxide-supported catalysts. 15 The MEA with a Pt/C anode with different Pt loadings was also tested. As shown in Fig.…”

“…Furthermore, the peaks of Ti( iii ) 2p 3/2 and Ti( iv ) 2p 3/2 lie at 457.1 eV and 458.5 eV, with a 5.7 eV splitting value variation. 15,41 According to the Ti 2p spectral analysis, the contents of Ti remain steady throughout the reversal test as the Ti( iii ) and Ti( iv ) contents fluctuate within 1%, which can be considered an experimental system error. The stable Ti( iii ) and Ti( iv ) contents indicate that the Ti 4 O 7 is hardly oxidized under high potential during the reversal test, consistent with previous research.…”

“…14,42 Moreover, the O 1s spectra are also examined to distinguish the peaks of lattice oxygen (530.0 eV), adsorbed oxygen species in the oxygen vacancies (531.4 eV), surface hydroxyl (532.4 eV), and surface water (533.8 eV). 15,43 The surface water peak emerges sharply after the reversal test, attributed to the water generated and adsorbed during the test. The oxygen adsorbed on the oxygen vacancy is still dominant even after the reversal tests, suggesting the prominent existence of Ti 4 O 7 .…”

“…In addition, the initial performance loss is inevitable for titanium oxide-supported catalysts due to the disadvantage of electronic conductivity compared to carbon. 14 Previous research tends to apply super-high anode Pt loadings to cover up the initial performance loss, such as 0.4 mg Pt cm −2 15 and 0.5 mg Pt cm −2 , 16 which is far from the practical application. Alternatively, carbon is added into titanium oxide-supported catalyst layers to offset the unsatisfactory electronic conductivity.…”