Grain boundary engineering for improved performance: A case study with Ni-superalloy on the hydrogen evolution reaction

• Grain boundary engineering has been employed for the first time in electrocatalysis. • Transfer of knowledge from Metallurgy to Catalysis led to activity-stability tradeoff. • Higher activity in engineered specimen is due to greater fraction of grain boundaries. • Higher stability in engineered specimen is due to greater fraction of Σ3 n boundaries. • Σ3 n boundaries restricted dissolution owing to its periodic nature. The present study investigates the impact of grain boundary engineering (GBE), a microstructural design strategy commonly employed in metallurgy to mitigate intergranular degradation, on the electrocatalytic performance of Ni-based alloys during the hydrogen evolution reaction (HER). The GBE-treated specimen exhibits higher HER activity than the as-received (AR) condition, primarily due to its increased fractions of grain boundaries (GBs) and total number of triple junctions (TJs), which serve as additional catalytic sites and facilitate charge transfer. Operando dissolution measurements using a scanning flow cell (SFC) in conjunction with inductively coupled plasma mass spectrometry (ICP-MS) reveal that, despite the enhanced activity, GBE-treated specimens show reduced dissolution compared to the AR condition. This improvement is attributed to a higher proportion of low-Σ coincidence site lattice (CSL) boundaries (Σ3 n (n ≤ 3); 79 ± 4 % in GBE vs. 55 ± 2 % in AR). Due to their higher periodicity, these boundaries are more resistant to dissolution, resulting in improved stability. These findings demonstrate that tailoring grain boundary character through GBE can result in a favorable balance between activity and stability, offering a promising approach to microstructural optimization in electrocatalysis.