Efficient Trimetallic Co–Ni–Mo Nanoparticles Anchored on Carbon Quantum Dots for Efficient Hydrogen Generation via Sodium Borohydride Hydrolysis

Abstract

A highly efficient trimetallic Co–Ni–Mo nanocatalyst supported on N-doped carbon quantum dots (Co–Ni–Mo@CQDs) was successfully synthesized via a hydrothermal-assisted chemical reduction strategy for H₂ generation through sodium borohydride (NaBH₄) hydrolysis. Systematic composition optimization demonstrated that Co₇₀Ni₂₅Mo₅@CQDs exhibited the highest catalytic activity among the investigated mono-, bi-, and trimetallic systems. Structural characterization by XRD, SEM, TEM, and EDX confirmed the successful formation of ultrasmall metallic nanoparticles with an average particle size of 6.12 ± 1.01 nm uniformly dispersed on the CQDs matrix without detectable phase segregation. The optimized catalyst achieved rapid H₂ evolution, reaching complete H₂ release (162 mL) within 15 min at a catalyst concentration of 100 mg L⁻¹. Kinetic investigations revealed an approximately first-order dependence on catalyst concentration (reaction order = 1.03) and a fractional reaction order with respect to NaBH₄ concentration (0.31), indicating a surface-controlled hydrolysis mechanism with rapid BH₄⁻ saturation on the catalyst surface. The catalyst exhibited a low apparent activation energy of 9.04 ± 0.87 kJ mol⁻¹, demonstrating highly favorable hydrolysis kinetics. Moreover, the optimized Co₇₀Ni₂₅Mo₅@CQDs catalyst exhibited a hydrogen generation rate (HGR) of 7,000 mL H₂ gcat⁻¹ min⁻¹. The remarkable catalytic performance is attributed to the synergistic interaction among Co, Ni, and Mo species together with the excellent dispersion and electron-transfer properties of the CQDs support. Furthermore, the catalyst maintained acceptable catalytic stability over 6 consecutive hydrolysis cycles, highlighting its potential as a low-cost, efficient alternative to noble-metal catalysts for on-demand H₂ production.

Graphical Abstract