Can Platinum Scale for PEC Hydrogen Evolution at the Terawatt Level?

Abstract

Recent years has seen enormous and impressive progress in the search for non-precious hydrogen evolution reaction (HER) catalysts for both electrolysis and photoelectrochemical water splitting (PEC) with the molybdenum sulfide– and the cobalt phosphide families of HER catalysts showing great potential [1]. Despite the progress, no non-precious catalyst which matches platinum in HER performance has yet been found. To a large degree, the hunt for non-precious HER catalysts is motived by the notion that the physical scarcity and high price of platinum precludes it from usage on the terawatt scale. Using numerical modelling supported by benchmarking experiments on very well-defined platinum-based PEC electrodes we demonstrate that platinum in principle offers sufficiently fast kinetics to be useful on the terawatt level. As may be seen in the insert in figure 1 just 54 tons of platinum (which corresponds to ca. 30% of the global annual production [2]) would in principle be enough to support 1 TW of HER at a PEC current density of 10 mA/cm2 at a modest overpotential of 50 mV.[3] We discuss the platinum requirement under different assumptions and also the potential problems of using platinum in real-world PEC systems. Refs[1] P.C.K. Vesborg, et al., J. Phys. Chem. Lett., 6, (6) p. 951-957, (2015)[2] P.C.K. Vesborg & T.F. Jaramillo, RSC Advances, 2, (21), p. 7933-7947, (2012)[3] E. Kemppainen et al., Energy & Environmental Science, 8, p. 2991-2999 (2015) Figure: Overpotential vs. of platinum loading for PEC-relevant current densities and (insert) total platinum requirement to implement 1 TW (average power, at a 15% capacity factor) of PEC hydrogen production. Figure 1