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The evolution of cost-effective hydrogen evolution reaction (HER) electrocatalysts is of great significance for the development of clean energy. Exploring effective synthesis strategies to optimize the performance of non-noble metal electrocatalysts has always attracted our attention. Herein, ultrathin coordination polymers were used as precursors to controllably synthesize two-dimensional (2D) ultrathin dual-phase transition metal selenide (TMSs)/carbon–nitrogen (CN) composites (CoSe2–NiSe2/CN) by a two-step method (first a low temperature hydrothermal method for selenization, and then high temperature calcination selenization). Benefiting from its large specific surface area (49 m2 g−1), abundant catalytically active sites and synergistic effects, CoSe2–NiSe2/CN can significantly enhance the HER catalytic activity and exhibits good electrocatalytic activity with an overpotential of 150 mV at −10 mA cm−2, and a small Tafel slope of 42 mV dec−1 in an acidic electrolyte for the HER. This work provides a new strategy for optimizing the HER catalytic activity of TMSs by preparing 2D ultrathin dual-phase TMS composite materials. [ABSTRACT FROM AUTHOR]

Highly active non-noble metal-based hydrogen evolution reaction (HER) electrocatalysts have attracted extensive attention in energy storage and conversion. Here, we reported the sub-4 nm ultrathin MoS 2 /Ni-Co 9 S 8 /CN nanosheet for alkaline HER. Due to the abundant heterointerfaces exposed to more effective active sites, the doping of Ni effectively ameliorated the electronic structure of Co 9 S 8 , the CN structure enhanced the electronic conductivity and improved the stability of the catalyst, the ultrathin MoS 2 /Ni-Co 9 S 8 /CN nanosheet shows good electrocatalytic activity with 96 mV at −10 mA·cm−2 in 1.0 M KOH solutions. Density functional theory (DFT) results verify that the abundant active heterogeneous nanosheets in MoS 2 /Ni-Co 9 S 8 /CN provide low H* -adsorption Gibbs free energy (Δ G H*). This study provides systematic theoretical and experimental evidence for the understanding of the effects of catalyst morphology, heterointerface, and composition control for HER electrocatalysts. • A new ultra-thin (3.1 nm) MoS 2 /Ni-Co 9 S 8 /CN hybrid electrocatalyst is synthesized. • MoS 2 /Ni-Co 9 S 8 /CN exhibits good electrocatalytic activity in alkaline with 96 mV at − 10 mA·cm−2. • Calculation verify that MoS 2 /Ni-Co 9 S 8 /CN has a highly active heterointerface for alkaline HER. [ABSTRACT FROM AUTHOR]