Impact of the alkalinity on the stability and catalytic activity of Ni/Nb2O5 composite electrodes for the hydrogen evolution reaction in NaCl solutions

Abstract

This study investigates the stability and catalytic activity of a Ni/Nb2O5 composite catalyst containing 13 wt.% Nb2O5 in 3.43 wt.% NaCl electrolytes with different concentrations of KOH (5.6, 15, and 30 wt.%). Results show that the addition of KOH significantly enhances the catalyst's stability, compared to NaCl alone. Furthermore, increasing KOH concentration decreases catalytic activity for HER, indicating that the electrolyte's alkalinization is a trade-off between stability and activity. The decline in catalytic activity is suggested to be due to a change in the reaction mechanism, from generating Cl2 to O2 as KOH concentration increases, favoring water decomposition over oxidation. Raman microscopy and UV–vis absorbance analysis show a decrease in surface oxidation with increasing KOH concentration. Using 3.43 wt.% NaCl with the addition of 5.6 or 15 wt.% KOH is feasible to increase electrode activity while maintaining electrocatalytic activity after aging in full hydrogen evolution, making it a good alternative electrolyte to replace KOH solutions. The findings have important implications for optimizing the synthesis of catalytic materials for H2 production and selecting electrolytes for long-term electrochemical cell operation.