• • Molten hydroxide salts (80% NaOH-20% Na2CO3) elevate central heating rate of microalgae pellets to 177 °C/s, mitigating thermal lag in large pellets and enabling faster conversion kinetics.
• • Porosity increases by 53.2%–104.3% within 10 s of reaction due to molten salt penetration and erosion, enhancing mass transfer and char reactivity.
• • Dominant reaction pathway shifts to char alkalization after only 70 s, indicating accelerated conversion and higher process efficiency.
• • Hydrogen yield from char alkalization improves markedly when heating rate is increased above 600 °C, attributed to synergistic catalytic and volatiles reforming effects.