Overflow phenomenon is widespread in heterogeneous catalytic reactions and has attracted much attention. In the catalytic process, not only the catalytic active center is in a dynamic change process, but also the overflow phenomenon shows that the migration and transmission of active species can not be ignored, which increases the complexity of catalysis. An in-depth understanding of the overflow effect is helpful to clarify the catalytic mechanism and is the prerequisite for the rational design of high-efficiency catalysts.

As a promising green energy, hydrogen has been paid more and more attention. Under the goal of carbon peaking and carbon neutralization, the status of hydrogen energy is gradually improved. High efficiency catalytic hydrogen production based on hydrogen storage materials is one of the most promising technologies for hydrogen storage and hydrogen production. However, in the multi-component catalyst catalyzed hydrogen production reaction, due to the difficulty of constructing a catalyst with clear structure and the limitation of in-situ characterization methods, the promotion mechanism of back overflow effect on catalytic performance is still unclear.

Gao Zhe and Qin Yong, researchers of Shanxi Institute of coal chemistry, Chinese Academy of Sciences, based on their previous understanding of the synergistic effect of hydrogen overflow (nature communications, 2019, 10, 4166; nature communications, 2020, 11, 4773; ACS catalyst, 2021, 11, 3159), further constructed a spatially separated NiO / Al2O3 / Pt two-component catalyst by using atomic layer deposition (ALD) technology, In situ X-ray absorption near edge structure (XANES) characterization revealed the hydrogen back overflow mechanism in aminoborane catalyzed hydrogen production. Relevant achievements were published on nature communications under the title of enhanced hydrogen generation by reverse spillover effects over bicomponent catalysts.

Using ALD technology, the research team constructed the spatially separated NiO / Al2O3 / Pt catalyst and compared the catalysts Al2O3 / Pt and NiO / Al2O3 (Fig. 1a-c). The hollow Al2O3 nanotube structure with a wall thickness of about 7 nm can be clearly observed. The high angle annular dark field scanning transmission electron microscope (HAADF-STEM) image and energy dispersive X-ray spectrum (EDX) of NiO / Al2O3 / Pt (Fig. 1D and E) show that Ni and PT are distributed on the outer wall and inner surface of Al2O3 nanotubes, respectively. The N2 adsorption isotherms and bjh pore size distribution curves of NiO / Al2O3, Al2O3 / Pt and NiO / Al2O3 / Pt catalysts show that these catalysts have similar pore structures.