Abstract
A couple of toluene (TL) and its hydrogenation product, methylcyclohexane (MCH), are promising high-density hydrogen carriers to store and transport large amounts of hydrogen. Electrochemical hydrogenation of TL to MCH can achieve energy savings compared with hydrogenation using molecular hydrogen generated separately, and development of highly active catalysts for electrochemical TL hydrogenation is indispensable. In this study, binary Pt3M (M = Rh, Au, Pd, Ir, Cu and Ni) alloy nanoparticle-loaded carbon catalysts were prepared by a colloidal method, and their activity for electrochemical TL hydrogenation was evaluated by linear sweep voltammetry. Each Pt3M electrode was initially activated by 100 cycles of potential sweep over a potential range of 0–1.2 or 0.8 V vs. reversible hydrogen electrode (RHE). For all activated Pt3M electrodes, the cathodic current density for electrochemical TL hydrogenation was observed above 0 V, that is the standard potential of hydrogen evolution reaction. Both specific activity, cathodic current density per electrochemical surface area, and mass activity, cathodic current density per mass of Pt3M, at 0 V for the Pt3Rh/C electrode were the highest, and about 8- and 1.2-times as high as those of the commercial Pt/C electrode, respectively, which could mainly be attributed to electronic modification of Pt by alloying with Rh. The Tafel slope for each activated Pt3M/C electrode exhibited the alloying of Pt with the second metals did not change the electrochemical TL hydrogenation mechanism.
Highlights
Most energy comes from fossil fuels, but the use of fossil fuels involves the generation of CO2
The hydrogen storage capacity of the TL/MCH couple is smaller than the other couples, but both TL and MCH are liquids at ambient temperature and pressure, so that existing infrastructure is available
This is why the TL/MCH couple was chosen as the hydrogen carrier in this study
Summary
Most energy comes from fossil fuels, but the use of fossil fuels involves the generation of CO2. Hydrogen gas has the disadvantage of low volumetric energy density (10.8 kJ L−1 under atmospheric conditions [2,3]), so there is an urgent need to develop hydrogen carriers that can store and transport large amounts of hydrogen. The hydrogen storage capacity of the TL/MCH couple is smaller than the other couples, but both TL and MCH are liquids at ambient temperature and pressure, so that existing infrastructure is available. This is why the TL/MCH couple was chosen as the hydrogen carrier in this study
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