Abstract
Currently, platinum-based electrocatalysts show the best performance for hydrogen evolution. All hydrogen evolution reaction catalysts should however obey Sabatier's principle, that is, the adsorption energy of hydrogen to the catalyst surface should be neither too high nor too low to balance between hydrogen adsorption and desorption. To overcome the limitation of this principle, here we choose a composite (rhodium/silicon nanowire) catalyst, in which hydrogen adsorption occurs on rhodium with a large adsorption energy while hydrogen evolution occurs on silicon with a small adsorption energy. We show that the composite is stable with better hydrogen evolution activity than rhodium nanoparticles and even exceeding those of commercial platinum/carbon at high overpotentials. The results reveal that silicon plays a key role in the electrocatalysis. This work may thus open the door for the design and fabrication of electrocatalysts for high-efficiency electric energy to hydrogen energy conversion.
Highlights
Platinum-based electrocatalysts show the best performance for hydrogen evolution
We report an approach to overcome the limitations dictated by the Sabatier’s principle by separating the adsorbing surface from the desorbing surface of hydrogen evolution reaction (HER) catalysts
We design metal/ SiNW composites as the catalysts in which the metal is the strongly hydrogen adsorbing surface and Si is the weakly adsorbing surface offering rapid evolution of hydrogen
Summary
Platinum-based electrocatalysts show the best performance for hydrogen evolution. One of the oldest rules in catalysis, Sabatier’s principle[11] states that for efficient HER the adsorption energy should be neither too high nor too low, because if it is too high (endothermic) adsorption is slow and the overall rate is slow as well. If it is too low (exothermic) desorption is slow[2,12]. To support our experimental findings we perform density functional theory (DFT) simulations of the Rh/SiNW system, which confirm the benefits of our composite approach of dividing the catalyst into two separate surfaces with large and small adsorption energies, respectively. High-angle annular dark field scanning TEM image of a single Rh NP attached to SiNW (Fig. 1c) and energy dispersive spectroscopy mapping show the elemental distribution of oxygen (red), silicon (orange) and rhodium (green), respectively (Fig. 1d)
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