Synergistic Enhancement of the Hydrogen Evolution Reaction by NiCu Catalyst on Defect-Rich TiO2 Supports: Differential Electrochemical Mass Spectrometry Insights

This study investigates the synergistic effect of NiCu catalyst supported on carbon-TiO 2 during the hydrogen evolution reaction (HER) in alkaline media. Ni 60 Cu 40 metallic ratios are supported on carbon Vulcan (NiCu/C) and on a modified carbon Vulcan matrix containing commercial TiO 2 (NiCu/C-T0) and defect-rich TiO 2 (NiCu/C-TD). The morphological, structural, and chemical compositions, as determined by XRD, STEM-EDX, XPS, and Raman, confirmed that TiO 2 in NiCu/C-TD possesses a relatively high concentration of Ti 3+ species (ca. 20%) when compared to NiCu/C-T0, indicating the presence of defective species in NiCu/C-TD. The defective functionality of C-TD is electrochemically demonstrated, with the NiCu/C-TD catalyst showing superior HER activity, as evidenced by differential electrochemical mass spectrometry (DEMS). This activity relates to charge-transfer within the catalyst, HER's low rate-determining step, and the electrochemical overpotential of the defective TiO 2 electrocatalyst. Overall, the catalytic activity is attributed to the synergistic interplay between NiCu and the defective-rich TiO 2 support, which modulates the adsorption/desorption of intermediates, facilitates interfacial electron transfer, and leads to a higher hydrogen production rate for NiCu/C-TD. These results provide a strategy for designing defect-rich HER electrocatalysts. An electrocatalyst composed of Ni and Cu nanoparticles on defect-rich TiO 2 and carbon enhances hydrogen evolution reaction (HER) activity in alkaline media. The presence of defects in TiO 2 facilitates electron transfer, thereby improving the electrocatalytic efficiency of hydrogen production. • Ni and Cu on carbon and defect-rich TiO 2 boosts alkaline HER activity. • Defective TiO 2 enhances electron transfer, promoting HER. • DEMS confirms H 2 generation for defect-rich TiO 2 -supported electrocatalyst.