Ga-doped Ni/Al2O3 catalyst reaches 92.0% ammonia conversion at 500 °C in lab tests

A research group from Zhengzhou University, together with colleagues from Henan Agricultural University, The Hong Kong Polytechnic University and the Chinese Academy of Sciences in Shanghai, reported in Nature Communications that trace gallium (Ga) doping markedly boosts the low-temperature activity of a Ni/Al2O3 catalyst for ammonia decomposition doi.orgNature Communicationsdoi.orgOpen source ↗. According to the authors, the Ga-doped catalyst achieves 92.0% ammonia conversion at 500 °C and a weight hourly space velocity (WHSV) of 30,000 mL gcat−1 h−1 doi.orgNature Communicationsdoi.orgOpen source ↗. The work is a laboratory study of the catalyst.

Ammonia as a hydrogen carrier

Ammonia is regarded as a promising hydrogen carrier for producing COx-free hydrogen. Its decomposition, however, suffers from high reaction temperatures, and this is the problem the study targets doi.orgNature Communicationsdoi.orgOpen source ↗. The authors describe the result as an efficient and stable Ni-based catalyst for low-temperature ammonia decomposition doi.orgNature Communicationsdoi.orgOpen source ↗.

Kinetic experiments showed that introducing Ga species alleviates hydrogen poisoning of the catalyst doi.orgNature Communicationsdoi.orgOpen source ↗. This is one of the effects the authors link to the improved activity at lower temperature.

Role of interfacial gallium

Further studies confirmed that Ga preferentially segregates on the catalyst surface and disperses around Ni nanoparticles doi.orgNature Communicationsdoi.orgOpen source ↗. The Ga species located at the interface facilitate hydrogen spillover from Ni to the Al2O3 support doi.orgNature Communicationsdoi.orgOpen source ↗.

According to the authors, this spillover promotes the enrichment of adsorbed N* species and reduces their recombination temperature on the Ni surface doi.orgNature Communicationsdoi.orgOpen source ↗. The title of the paper attributes the enhancement to interfacial Ga3+.

The authors present the work as a strategy for optimizing catalytic performance by regulating interfacial hydrogen transfer doi.orgNature Communicationsdoi.orgOpen source ↗. The reported conversion was measured under the stated conditions of 500 °C and WHSV = 30,000 mL gcat−1 h−1; the abstract gives no other test conditions or figures.