Pt and Ru electrocatalysts using the synergistic effect of single atoms and nanoparticles for high hydrogen evolution

Abstract

Hydrogen has been considered as a clean renewable energy system. Pt has been the universal choice for the acidic hydrogen evolution reaction (HER), 2H+ + 2e–→H2↑, because Pt displays a much lower overpotential and higher current density than other materials. For cost efficiency, the development of non-precious materials has also been in progress, but yet Pt is still the universal choice. Also, milligram Pt loadings for a high HER activity are being developed, but an ~1μg loading for an inexpensive and highly efficient hydrogen production has not yet been realized. Herein we adopt an atomic-scale engineering strategy for Pt-based catalysts with the controlled deposition of Cu, Fe and Co atoms onto/into graphitic tubes (GTs). This has led us to develop the HER catalyst in which GTs encapsulate FeCo alloy nanoparticles (NPs) with an ultrathin Cu layer inside the tube wall and have single Pt atoms embedded at the GT outlayer and nanosized Pt clusters on the tube surface. The catalyst with only 1.4μg of Pt (per electrode area (cm2)) loading is found to exhibit a superior HER activity with a very high turnover frequency (TOF) and both a small overpotential and stability. With a 1/80th Pt loading of a commercial 20% Pt/C catalyst, in 0.5 M H2SO4 the catalyst achieves a current density of 10 mA cm−2 at an overpotential of 18 mV, and shows a turnover frequency of 7.22 s−1 (96 times higher than that of the Pt/C catalyst) and long-term durability (10,000 cycles). The catalytic activity is enhanced due to the synergistic effect between the Pt clusters and single Pt atoms.