A Pt cathode with high mass activity for proton exchange membrane water electrolysis

Abstract

To reduce the fabrication cost of proton exchange membrane water electrolyzers (PEMWEs), low-loading platinum-based cathodes were fabricated through constant potential (−1.1 VSCE) electrodeposition of Co, galvanic displacement with Pt in K2PtCl4 + NaCl solution, and subsequent chemical (immersion in 0.5 M H2SO4 for 5 min) or electrochemical dealloying (2000 potential cycles at −0.2 to −0.5 VSCE in 0.5 M H2SO4) processes. These simple electrochemical steps produced a bimodal structure of layered Pt/Co/carbon paper (CP) and particulate Pt/CP catalysts on a porous transport layer of carbon fiber. Heat treatment of Co deposits (500 °C for 2 h, H2/Ar atmosphere) prior to Pt displacement was found to strongly affect the stability of Co and the electronic structures of subsequently placed Pt, resulting in high activity (an overpotential of 18.4 mV at −10 mA cm−2) and durability (∼6000 potential cycles) of the electrochemically dealloyed catalyst in hydrogen evolution reaction. A single cell with this catalyst at low cathode Pt loading of 18.4 μg cm−2 further demonstrated excellent performance of 2.39 A cm−2 @ 1.9 V. The cathode Pt mass activity is superior to previous works on other low Pt electrode fabrication methods using pulse electrodeposition or self-terminated electrodeposition, providing a new lower limit of precious metal usage for PEMWE.