Hollow nickel particles were synthesized via ultrasonic spray pyrolysis using ethanol or sucrose as the reducing agents, and nickel nitrate precursor solution in a temperature range of 500 to 800 degrees C. At 500-600 degrees C hcp Ni was the main synthesis product, and at 700-800 degrees C fcc Ni was formed. Ethanol effectively lowered the particle and crystallite sizes. The synthesized sample with ethanol at 700 degrees C had a specific surface area of 106 m(2)/g with a non-uniform meso/macroporous structure. The catalytic activity of the synthesized Ni particles for dry reforming of CH4 at 750 degrees C yielded 90% for the conversion of CH4. Al2O3 was also added to the precursor solution to provide active support for Ni particles. The synthesized Ni/Al2O3 particles yielded 89% and 70% conversion for CH4 and CO2, respectively, which shows the hollow structures of Ni combined with Al2O3 support is effective for the dry reforming of CH4. (C) 2019 Elsevier B.V. All rights reserved.