Interface engineering of Co2B–MoO3/MOF heterojunctions with rich cobalt defects for highly enhanced NaBH4 hydrolysis

Abstract

Sodium borohydride (SBH) is a promising hydrogen storage material, but efficient catalysts for H₂ generation from its hydrolysis are needed for practical use. In this work, a self-sacrificial template strategy was employed to synthesize Co₂B–MoO₃/MOF heterojunction materials with rich cobalt defects on MOF substrates. The optimal Co₂B–MoO₃/MOF catalyst exhibited a rapid hydrogen generation rate of 6893.1 mL min⁻¹ g_cat⁻¹ at 25 °C, outperforming most non-precious metal catalysts. Studies found that the higher work function (6.94 eV) and charge attraction properties (−15.75 mV) endow the Co₂B-MoO₃/MOF catalyst with a strong adsorption capacity for negatively charged BH₄⁻. Based on the Michaelis–Menten model, a Co₂B–MoO₃/MOF-catalyzed mechanism for the hydrolysis of NaBH₄ to generate H₂ was proposed, in which Co₂B and MoO₃ effectively activate the BH₄⁻ and H₂O molecules, respectively. Moreover, a highly selective “on–off” switch was achieved via a Zn²⁺/EDTA-2Na system for on-demand H₂ evolution upon NaBH₄ hydrolysis. Hydrogen generated from NaBH₄ hydrolysis by the Co₂B–MoO₃/MOF catalyst was used directly to drive a custom H₂–air fuel cell, successfully powering an electric fan and demonstrating its potential for practical applications.