Regulating the electronic structure of dual active site Co/MoOx-cCNT for catalyzing NaBH4 hydrolysis towards controllable high-capacity hydrogen production

Abstract

Hydrolysis of solid NaBH₄ is a prospective technique towards on-site hydrogen requirements. The hydrogen generation efficiency, controllability, and stability of hydrolysis process plays a fundamental role for its practical orientation. In this article, we report the manipulation of dual-active-site Co/MoO_x-cCNT catalysts with regulated electronic structure and explore its potential for boosting large-scale H₂ production through hydrolysis of solid NaBH₄ for the first time. A combination of DFT calculations and systematic characterizations with kinetic isotopic analysis reveal that the outstanding catalytic performance is attributed to the dual-active-site of Co and MoO_x, which enabled the co-activation of NaBH₄ and H₂O. The incorporation of cCNT provides a fast conduction channel, which accelerates the electron conduction at the microscopic level and enriches the electron density on the active site surface. The hydrogen generation rate of optimal Co/5MoO_x-cCNT catalyst exhibits an exceptional high HGR value of 8795.4 ml min⁻¹ ${\text{g}}_{\text{cat}}^{\text{-1}}$${\text{g}}_{\text{cat}}^{\text{-1}}$ with an activation energy as low as 11.7 kJ mol⁻¹. Furthermore, the studied catalyst can endure a water-limited environment without catalytic decay and reduce the heat accumulation during hydrolysis, which is attributed to the presence of cCNT, significantly accelerating the mass and heat transfer between multiphase interface of reactants. In the following long-duration hydrogen production test, an average hydrogen supply rate of 5.7 SLPM over 213 min, which is the highest level achieved by a single reactor based on the available international literature. The system archives the GHSC and VHSC as high as 5.7 wt% and 70 g/L, respectively, meeting the US DOE targets for 2025. Our study provides a comprehensive exploration of the catalytic NaBH₄ hydrolysis mechanism and its potential for practical application. The strategy demonstrated here could shed a new light on the mitigation of issues such as poor stability and controllability of hydrolysis in solid state, marking a substantial stride toward industrializing NaBH₄ hydrolysis.