Ni(PO₃)₂/CNTs hybrid architecture via phthalocyanine modulated self-assemblies for efficient hydrogen evolution reaction

Reasonable design and facile synthesis of high-efficiency non-noble electrocatalysts for hydrogen evolution reaction (HER) in water splitting are crucial for renewable and clean energy technologies. Increasing the number of active sites via nanostructuring is a fundamental method to promote the HER activity of the catalysts. However, the balance between the exposed active sites and the stability cannot be well maintained due to the aggregation of nanoscale catalysts. Therefore, it is imperative to combine effective active compounds with suitable carbon materials to stabilize nanomaterials. Hence, a hybrid architecture with Ni(PO₃)₂ nanoparticles ladened on the carbon nanotubes (Ni(PO₃)₂/CNTs) was elaborately designed and synthesized by pyrolyzing the nickel phthalocyanine (NiPc)/CNTs assemblies and subsequent phosphidation. The π-π interaction between NiPc and CNTs is conductive to the tight attachment of the active species to the substrate, while the inlaid structure effectively prevents the corrosion/aggregation of Ni(PO₃)₂ nanoparticles and ensures the stability of the catalyst. Accordingly, Ni(PO₃)₂/CNTs displayed excellent HER performances with remarkable stability both in 1.0 M KOH and 0.5 M H₂SO₄ with overpotentials of 71 mV and 87 mV at 10 mA cm⁻², respectively. The Tafel slopes of Ni(PO₃)₂/CNTs in alkaline and acid medium were 65 mV dec^-1 and 46 mV dec^-1, respectively, both exposed a Volmer-Heyrovsky mechanism during the HER. The present work will shed new light on the exploitation of non-noble metal high-efficiency HER electrocatalysts.