Supercritical water gasification (SCWG) is hopefully to be an acceptable choice for hydrogen production, the hydroxide ion assisted water gas shift reaction (WGSR) has been regarded as the most important reaction to generate hydrogen during the process. However, the principle of practical OH⁻ catalyzed reaction is not possible to acquire by experiments. Thus, density functional theory (DFT) is utilized to investigate the reaction mechanism theoretically in this work. Through first principle calculations, every species and energy barrier for elementary steps are achieved, and formate ion is determined as the important intermediate. Besides, HCOO⁻ + H₂O → HCO₃⁻ + H₂ is the dominant path to generate hydrogen, as well as the rate-determining step with 47.94 kcal/mol energy barrier. Furthermore, the reaction rate constant is calculated to be k_catalytic(s⁻¹) = 2.34 × 10¹²exp(−1.80 × 10⁵/RT) using transition state theory with Wigner transmission coefficient (TST/w). Lastly, supercritical water condition is demonstrated to be a favored media for WGSR, because it may dissociate, dissolve or hydrolyze more hydroxide anion than conventional steam. The results are expected to benefit the control of reaction process and the design of SCWG reactor.

超临界水气化（SCWG）有望成为制氢的可接受选择，氢氧根离子辅助的水煤气变换反应（WGSR）被认为是该过程中产生氢的最重要反应。然而，实际的OH的原理^-催化的反应是不可能通过实验获取。因此，在这项工作中，利用密度泛函理论（DFT）从理论上研究了反应机理。通过第一原理计算，可以实现基本步骤的每种物质和能垒，并且甲酸根离子被确定为重要的中间体。此外，HCOO ^-  + H ₂ O→HCO ₃ ^-  + H ₂是产生氢的主要途径，也是具有47.94 kcal / mol能垒的速率确定步骤。此外，使用具有维格纳透射系数（TST / w）的过渡态理论，将反应速率常数计算为k_催化（s ^-1）＝ 2.34×10 ¹² exp（-1.80×10 ⁵ / RT）。最后，事实证明，超临界水条件是WGSR的首选介质，因为与常规蒸汽相比，它可以分解，溶解或水解更多的氢氧根阴离子。预期结果将有利于反应过程的控制和SCWG反应器的设计。