Boride-mediated and carbon nanotube-scaffolded synthesis of cobalt-based electrocatalyst for efficient and stable alkaline hydrogen evolution at industrial-scale current density†

Abstract

Tailored synthesis of earth-abundant alkaline hydrogen evolution electrocatalysts, featuring optimized metal/oxide heterointerfacial structures and rapid charge-/mass-transfer characteristics, remains a significant challenge in advancing water electrolysis as a viable technology for sustainable hydrogen production. Herein, we report the boride-mediated and carbon nanotubes (CNT)-scaffolded synthesis of a cobalt-based electrocatalyst that can effectively address the key factors influencing alkaline HER performance. Specifically, a cobalt foam (CF) supported composite catalyst (Co/CoO/CNT) was prepared via a three-step procedure: (1) combustion synthesis of CNT networks on a CF surface, (2) electroless plating of the boride precursor onto the surface of CNT-decorated CF, and (3) annealing treatment to induce solid-phase reaction between the boride and adjacent CoO. The boride-mediated synthesis allows for the formation of abundant Co/CoO heterointerfacial boundaries, which serve as active sites for alkaline HER. The pre-growth of CNT networks enables the construction of a hierarchical mesoporous–macroporous architecture, rendering improved active site accessibility and enhanced water transport and gas release in the catalyst layer. In addition, the incorporation of conductive CNTs helps improve charge-transfer kinetics. Benefiting from these favorable attributes, the Co/CoO/CNT/CF catalyst showed excellent alkaline HER performance, requiring only 17 and 185 mV overpotentials to afford current densities of 10 and 500 mA cm⁻², respectively, and maintaining long-term stability at high current densities up to 1000 mA cm⁻². Furthermore, the catalyst exhibited fairly good performance in alkaline natural seawater electrolysis, enabling stable hydrogen production at 500 mA cm⁻² for over 100 hours.