Operando Insights on the Degradation Mechanisms of Rhenium-doped and Undoped Molybdenum Disulfide Nanocatalysts for Electrolyzer Applications

TL;DR

This study investigates the degradation mechanisms of rhenium-doped and undoped MoS2 nanocatalysts in PEM electrolyzers, using operando techniques to correlate electrochemical performance with structural stability, highlighting doping as a strategy for durability.

Contribution

The paper provides the first detailed operando analysis of degradation mechanisms in Re-doped and undoped MoS2 catalysts, linking structural evolution to electrochemical stability.

Findings

Re-doped MoS2 exhibits enhanced stability under HER conditions.

Degradation initiates at electrolyte contact and varies with doping.

Doping improves both activity and durability of MoS2 catalysts.

Abstract

MoS2 nanostructures are promising catalysts for proton-exchange-membrane (PEM) electrolyzers to replace expensive noble metals. Their broadscale application demands high activity for the hydrogen evolution reaction (HER) as well as robust durability. Doping is commonly applied to enhance the HER activity of MoS2-based nanocatalysts, but the effect of dopants in the electrochemical and structural stability is yet to be discussed. Herein, we correlate operando electrochemical measurements to the structural evolution of the materials down to the nanometric scale by identical location electron microscopy and spectroscopy. The range of stable operation for MoS2 nanocatalysts with and without rhenium doping is experimentally defined. The responsible degradation mechanisms at first electrolyte contact, open circuit stabilization and HER conditions are experimentally identified and confirmed with the calculated Pourbaix diagram of Re-doped MoS2. Doping MoS2-based nanocatalysts is validated as a promising strategy for the continuous improvement of high performance and durable PEM electrolyzers.