The rational design of the catalysts with easily-accessible surface and high intrinsic activity is desirable for electrocatalytic hydrogen evolution reaction (HER). Here, we reported the construction of two-dimensional (2D) Co-Mo nitrides based heterojunctional catalyst for efficient HER based on a “mediated molecular” assisted route. The 2D Co(OH)₂ sheet reacted partially with the “mediated molecular” (2-methylimidazole (2-MIM)) to form zeolitic imidazolate framework (ZIF)-67 at surface, giving ZIF-67/Co(OH)₂ sheets. The ZIF-67 combines with [PMo₁₂O₄₀]³⁻ cluster (PMo₁₂) due to the interaction of mediated molecular with PMo₁₂, producing 2D Mo-Co-2MIM/Co(OH)₂ bimetallic precursor. After controlled nitriding, the Mo₂N islands dispersed on 2D porous Co-based sheets were formed. A series of characterizations and density functional theory (DFT) calculation indicated the formation of a close contact interface, which promotes the electron transfer between Mo and Co components, enhances the electron migration/redistribution and redistribution and down-shift of d-band center and thus gives a high intrinsic activity. The 2D characteristics make the catalyst more accessible contact sites, which is favourable to promot the HER. The tests showed that the optimized catalyst exhibits an onset potential of 0 mV and an overpotential of 10 mA·cm⁻² at 35.0 mV, which is quite close to that of Pt/C catalyst. It also exhibits an activity superior to Pt/C at high current density (> 100 mA·cm⁻²). A good stability of the catalyst was achieved with no significant decay for 100 h of continuous operation. The electrolytic cell composed of optimized catalyst and P-NiFe-layered double hydroxide (LDH) can be driven by low voltage (only 1.47 V) to reach a current density of 10 mA·cm⁻².

FeNi-based phosphides are one of the most hopeful electrocatalysts, whereas the significant challenge is to achieve prominent bifunctional catalytic activity with low voltage for water splitting. The morphology and electronic structure of FeNi-based phosphides can intensively dominate effective catalysis, therefore their simultaneous regulating is extremely meaningful. Herein, a robust bifunctional catalyst of Zn-implanted FeNi-P nanosheet arrays (Zn-FeNi-P) vertically well-aligned on Ni foam is successfully fabricated by Zn implanting strategy. The Zn fulfills the role of electronic donor due to its low electronegativity to enhance the electronic density of FeNi-P for optimized water dissociation kinetics. Meanwhile, the implantation of Zn into FeNi-P can effectively regulate morphology of the catalyst from thick and irregular nanosheets to ultrathin lamellar structure, which generates enriched catalytic active sites, leading to accelerating electron/mass transport ability. Accordingly, the designed Zn-FeNi-P catalyst manifests remarkable hydrogen evolution reaction (HER) activity with low overpotentials of 55 and 225 mV at 10 and 200 mA·cm⁻², which is superior to the FeNi-P (82 mV@10 mA·cm⁻² and 301 mV@200 mA·cm⁻²), and even out-performing the Pt/C catalyst at a high current density > 200 mA·cm⁻². Moreover, the oxygen evolution reaction (OER) activity of Zn-FeNi-P also has dramatically improved (207 mV@10 mA·cm⁻²) comparable to FeNi-P (221 mV@10 mA·cm⁻²) and RuO₂ (239 mV@10 mA·cm⁻²). Noticeably, an electrolyzer based on Zn-FeNi-P electrodes requires a low cell voltage of 1.47 V to achieve 10 mA·cm⁻², far beyond the catalytic activities of FeNi-P||FeNi-P (1.51 V@10 mA·cm⁻²) and the benchmark RuO₂||Pt/C couples (1.56 V@10 mA·cm⁻²). This Zn-implanting strategy paves a new perspective for the development of admirable bifunctional catalysts.