CNT-integrated MoO₃ nanoparticles for bifunctional electrocatalytic oxygen and hydrogen evolution reactions

The escalating global demand for sustainable and clean energy urges the development of efficient electrocatalysts to overcome sluggish oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) kinetics in overall water splitting. This study investigates the key role of interfacial engineering by integrating orthorhombic α-MoO₃ nanoparticles with conductive carbon nanotubes (CNTs) to form a MoO₃@CNTs nanocomposite and systematically compares it with pristine MoO₃ to address conductivity-limited electrochemical performance. The underlying poorly conductive MoO₃ is employed as a reference system to evaluate the impact of CNT incorporation on charge-transfer resistance, active-site accessibility, and overall bifunctional catalytic efficiency. The electrochemical evaluation trends in relation to overpotential, Tafel slopes, double-layer capacitance (C _dl), electrochemically active surface area (ECSA), and charge-transfer resistance (R _ct) are revealed with significantly improved outputs. Among the investigated materials, MoO₃@CNTs performs remarkably better than pristine MoO₃, achieving low overpotentials of 0.35 V for the OER (50 mA cm^-2) and 0.33 V for the HER (-10 mA cm^-2) in 1 M KOH, compared to 0.42 V and 0.40 V for MoO₃, respectively. This study also reveals the enhanced electrocatalytic behavior of MoO₃@CNTs, mainly due to improved electronic conductivity and increased active-site exposure induced by CNT integration, leading to reduced Tafel slopes (217 mV dec^-1 for OER and 170 mV dec^-1 for HER), lower R _ct (5.1 Ω vs. 10.3 Ω), and higher C _dl (26.07 mF cm^-2 vs. 19.85 mF cm^-2) and ECSA (43.71 cm² vs. 30.43 cm²). These findings deepen the understanding of CNT-based interfacial engineering and its effect on MoO₃ electrochemical activity and position MoO₃@CNTs as a promising bifunctional catalyst for efficient and sustainable hydrogen production.