Insertion of carbon skeleton in Ni/MoO₂ heterojunction with porous hollow sphere for efficient alkaline electrochemical hydrogen production

The catalyst morphology has a strong impact on the activity of electrocatalytic hydrogen production. Considering the effect, we design and fabricate hollow spherical Ni/MoO₂ heterojunction. In addition, an amorphous carbon skeleton is inserted into the hollow sphere, which makes the structure more stable and porous. Compared with other morphological Ni/MoO₂, the porous hollow spherical Ni/MoO₂ (H-Ni/MoO₂) with an internal carbon skeleton shows better hydrogen evolution reaction (HER) activity with a small overpotential of 58 mV to reach 10 mA cm⁻² and a tafel value of 44.8 mV dec^-1 in alkaline media. The developed HER performance of H-Ni/MoO₂ can be attributed to the larger active surface area of porous hollow spherical structure and the faster electron transfer and better stability of carbon skeleton. Undoubtedly, the urea plays a crucial role to construct the hollow spherical morphology and being decomposed to form holes and amorphous carbon in the synthesized steps. The soft-template strategy using urea as the addition for forming the porous hollow structure with carbon skeleton can be extended to explore superior non-noble metal for hydrogen production.