Nano-and micro-sized ZnO samples were synthesized by the sol–gel method. Physical and thermal stability of ZnO samples were tested in supercritical water (SCW) and supercritical water gasification (SCWG) of formaldehyde. ZnO calcined at 350 °C (ZnO-350) has spherical particles with an average diameter of 150 nm. After SCW and SCWG treatments, the particle size of ZnO-350 increased and its roughness decreased as a result of agglomeration. Increasing the calcination temperature of ZnO from 350 to 900 °C increased crystallinity and the estimated crystal size of ZnO. The particles of ZnO calcined at 900 °C converted to hexagonal particles from spherical particles by the dissolution of coke precursors in SCW. Compared with the non-catalytic gasification of formaldehyde, the presence of ZnO increased the conversion of formaldehyde and hydrogen formation. The increasing calcination temperatures of ZnO enhanced hydrogen formation, which might be due to the formation of oxygen vacancies on the ZnO_1-x.

通过溶胶-凝胶法合成纳米和微米尺寸的 ZnO 样品。在超临界水 (SCW) 和超临界水气化 (SCWG) 甲醛中测试了 ZnO 样品的物理和热稳定性。在 350 °C 下煅烧的 ZnO (ZnO-350) 具有平均直径为 150 nm 的球形颗粒。SCW 和 SCWG 处理后，ZnO-350 的粒径增加，粗糙度降低，这是团聚的结果。将 ZnO 的煅烧温度从 350 °C 提高到 900 °C，会增加 ZnO 的结晶度和估计的晶体尺寸。通过焦炭前驱体在 SCW 中的溶解，在 900 °C 下煅烧的 ZnO 颗粒从球形颗粒转化为六边形颗粒。与甲醛的非催化气化相比，ZnO的存在增加了甲醛的转化和氢气的形成。_1-x。