Fabrication of a Robust PEM Water Electrolyzer Based on Non‐Noble Metal Cathode Catalyst: [Mo₃S₁₃]²⁻ Clusters Anchored to N‐Doped Carbon Nanotubes

Abstract

High investment costs and a dependence on noble metal catalysts currently obstruct the large-scale implementation of proton exchange membrane water electrolyzers (PEMWEs) for converting fluctuating green electricity into chemical energy via water splitting. In this context, this work presents a high-performing and stable non-noble metal catalyst for the hydrogen evolution reaction (HER), consisting of [Mo₃ S₁₃ ]^2- clusters supported on nitrogen doped carbon nanotubes (NCNTs). Strikingly, a significant electrochemically induced activation of the Mo₃ S₁₃ -NCNT catalyst at high current densities is observed in full cell configuration, enabling a remarkable current density of 4 A cm^-2 at a cell voltage of 2.36 V. To the authors' knowledge, this is the highest reported value to date for a PEMWE full cell using a non-noble metal HER catalyst. Furthermore, only a minor degradation of 83 µV h^-1 is observed during a stability test of 100 h constant current at 1 A cm^-2 , with a nearly unchanged polarization behavior after the current hold. Catalyst stability and activity are additionally analyzed via online dissolution measurements. X-ray photoelectron spectroscopy examination of the catalyst before and after electrochemical application reveals a correlation between the electrochemical activation occurring via electrodissolution with changes in the molecular structure of the Mo₃ S₁₃ -NCNT catalyst.