Morphology engineering of hollow core@shell structured CoO@CuO-NiO for fast hydrogen release from ammonia borane methanolysis.

Catalytic methanolysis of ammonia borane is an integrated hydrogen production/storage technology with bright prospects, while its wide application is impeded by the high-cost of catalysts. In this work, hollow core@shell structured (HCSS) CoO@CuO-NiO with a size of 300-500 nm and a shell thickness of ca. 100 nm has been designed for ammonia borane (NHBH) methanolysis for rapid hydrogen release. The possible formation mechanism of HCSS-CoO@CuO-NiO is proposed based on a series of characterization results, which is crucial for the design and preparation of nanocatalysts with similar architectures. Benefiting from the optimized compositions and electronic structures, the best HCSS-CoO@CuO-NiO sample exhibits high catalytic activity in NHBH methanolysis with a turnover frequency of 67.1 min, surpassing that of all the noble-metal-free catalysts in previous reports. A possible reaction mechanism of NHBH methanolysis is put forward based on the in-situ Fourier transform infrared spectrometer (FTIR) characterization and kinetic isotope effect (KIE) experimental results. This work supplies a novel avenue for developing cheap and robust catalysts towards NHBH methanolysis by tailoring the catalysts' morphology to hollow core@shell structures.