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Probing the nanoscale structure of the catalytically active overlayer on Pt alloys with rare earths, Nano Energy, http://dx.

Platinum rare earth alloys have proven both active and stable under accelerated stability tests in their bulk polycrystalline form. However, a scalable method for the synthesis of high surface area supported catalyst of these alloys has so far not been presented. Herein we discuss the thermodynamics relevant for the reduction conditions of the rare earths to form alloys with platinum. We show how, the tolerances for water and oxygen severely limits the synthesis parameters and how under certain conditions the thermal reduction of YCl3 with H2 is possible from 500 ˚C. From the insight gained, we synthesized a PtxY/C by modifying a Pt/C catalyst, and confirmed alloy formation by both x-ray diffraction and x-ray photoelectron spectroscopy measurements. These reveal crystalline intermetallic phases and the metallic state of yttrium.Without any optimisation to the method, the catalyst has an improved mass activity compared to the unmodified catalyst, proving the viability of the method. Initial work based on thermodynamic equilibrium calculations on reduction time show promise in controlling the phase formed by tuning the parameters of time, temperature and gas composition.

Proton exchange membrane fuel cell (PEMFC) technology has reached pre-commercial viability, but their insufficient durability acts as a major roadblock in its full-fledged utilization. It has been well established that the issue of durability is majorly due to the corrosion of carbon support used for Pt. Therefore, a search for low-cost and robust alternative support is highly desirable. In this paper, different graphite (and graphene) materials as durable support for Pt-based electrocatalyst are investigated. We followed the topdown approach where a fully graphitized support is mildly wet-milled and surface-treated to give a sufficient surface modification for improved Pt deposition on these supports. All the graphite-supported Pt samples showed better durability than that of state-of-the-art commercial electrocatalysts. Considering both activity and durability the best catalyst among the investigated samples showed a comparable mass specific activity (MSA) of 0.186 A/mg and significantly higher durability (70%) after 7500 stress cycles. For HiSpec9100 and BASF commercial electrocatalysts, the normalized ESA retention value after 7500 stress cycles was 40% and 47%, respectively.

Microwave-assisted heterogeneous catalysis (MHC) is gaining attention due to its exciting prospects related to selective catalyst heating, enhanced energy-efficiency, and partial inhibition of detrimental side gas-phase reactions. The induced temperature difference between the catalyst and the comparatively colder surrounding reactive atmosphere is pointed as the main factor of the process selectivity enhancement towards the products of interest in a number of hydrocarbon conversion processes. However, MHC is traditionally restricted to catalytic reactions in the absence of catalyst coking. As excellent MW-susceptors, carbon deposits represent an enormous drawback of the MHC technology, being main responsible of long-term process malfunctions. This work addresses the potentials and limitations of MHC for such processes affected by coking (MHCC). It also intends to evaluate the use of different catalyst and reactor configurations to overcome heating stability problems derived from the undesired coke deposits. The concept of long-term MHCC operation has been experimentally tested/applied to for the methane non-oxidative coupling reaction at 700 °C on Mo/ZSM-5@SiC structured catalysts. Preliminary process scalability tests suggest that a 6-fold power input increases the processing of methane flow by 150 times under the same controlled temperature and spatial velocity conditions. This finding paves the way for the implementation of high-capacity MHCC processes at up-scaled facilities.

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