Role of cobalt precursors in modulating the activity and stability of Nb2O5-Based catalysts for sustainable hydrogen production

Designing active and stable catalysts for hydrogen generation from sodium borohydride (NaBH 4 ) hydrolysis is critical for advancing sustainable hydrogen technologies. This study reveals how the choice of cobalt precursor governs the dispersion, oxidation state, and interfacial chemistry of Nb 2 O 5 /Co composites, directly impacting their catalytic activity and durability. Structural and surface analyses (XRD, FTIR, BET, XPS, DLS) demonstrate that the identity of the cobalt precursor strongly modulates cobalt–niobia interfacial interactions, as evidenced by precursor-dependent O1s chemical shifts and Nb oxidation-state changes in XPS, reflecting modifications in the local surface electronic environment. The composite prepared with cobalt sulfate (Nb 2 O 5 /Co–S) exhibited the highest hydrogen generation rate (0.30 L H 2 min −1 g −1 at 25 °C) and maintained high activity after four cycles, while Nb 2 O 5 /Co–N, despite its larger surface area (67 m 2 g −1 ), displayed inferior performance. XPS evidenced partial reduction of Nb 5+ to Nb 4+ in Nb 2 O 5 /Co–S, indicating stronger metal-support electronic interactions that stabilize active cobalt species. These findings demonstrate that precursor-controlled interfacial engineering, rather than surface area, dictates catalytic behavior.