Ag/Ti-suboxides as non-PGM anode electrocatalyst for PEM water electrolysis

Abstract

Minimization of high-cost metal electrocatalyst is necessary to achieve cost-effective green hydrogen production by proton exchange membrane (PEM) water electrolysis (WE). The large increase of the cost of Ir recently observed requires individuating alternative catalyst solutions for the oxygen evolution reaction (OER) in PEMWE. The OER is the rate determining step of the electrolysis process requiring high-cost noble metals with significantly high loading. A non-platinum group metal (non-PGM) anode catalyst based on silver and titanium suboxide was prepared and used for the oxygen evolution reaction in a PEMWE cell. By using a solid-state synthesis procedure, a silver nitrate and titanium suboxides (TinO2n-1) with Magneli phase powders were mixed and subjected thereafter to a thermal treatment at 300 °C in a 50% H2/N2 gas stream to promote the inclusion of silver within the Ti-suboxides structure. A membrane – electrode assembly (MEA), consisting of the anode Ag/TinO2n−1 and conventional Pt/C cathode catalysts deposited on a 212 NAFION® membrane (thickness 50 μm), was investigated to assess the performance and durability of the PGM free oxygen evolution catalyst in an acidic environment.A promising performance, of 0.6 A cm−2 at 2 V/cell at 80 °C, and an excellent stability (degradation rate < 14 μV/h during a 1000 h test) were achieved for the electrolysis cell based on a cost-effective metal anode electrocatalyst.