In situ synthesized low-PtCo@porous carbon catalyst for highly efficient hydrogen evolution

Abstract

Electrochemical water splitting is a sustainable method for producing hydrogen - the ultimate clean energy carrier. However, high cost and poor stability of the Pt catalyst for hydrogen evolution reaction (HER) hinder its wide applications. Here, we report a facile approach to synthesize an ultra-low PtCo bimetallic catalyst embedded in porous carbon via direct annealing of Pt-doped ZIF-67. The resulting catalyst (CPt@ZIF-67) with only 5 wt% Pt loading exhibits better performance than commercial 20 wt% Pt/C, achieving a Tafel slope of 27.1 mV dec-1 with an overpotential of only 50 mV at current density of 10 mA cm-2. Theoretical simulations show that carbon cages generated over the bimetal clusters during annealing dramatically reduce the free energy for HER. The free energy does not reduce proportionally with increasing Pt loading, implying the need to ensure appropriate Pt placement on surfaces, rather than simply raising Pt level, in order to enhance effectiveness of a Pt-based catalyst. The study provides a viable approach for developing cost-effective Pt-related catalysts for HER.