Tailoring electron redistribution and hydrogen adsorption in an epitaxial MnTe/Cr ₂ Te ₃ semiconductor/metal heterojunction for highly efficient hydrogen evolution catalysis

Electronic structure engineering and interface chemistry are critical for optimizing hydrogen evolution reaction (HER) electrocatalysts. Here, we report a solution-based synthesis of Cr-doped MnTe nanowires and a Cr₂Te₃/MnTe/Cr₂Te₃ metal/semiconductor/metal heterojunction that achieves outstanding HER performance. The epitaxial interface, defined by coherent lattice alignment between MnTe and Cr₂Te₃, enables directional electron transfer from the metallic Cr₂Te₃ caps to the MnTe semiconductor, as supported by XPS and Bader charge analyses. DFT calculations reveal that Cr doping enhances conductivity and introduces active electronic states, while the heterojunction simultaneously optimizes hydrogen adsorption free energy (ΔG_H*) and reduces HER barriers. As a result, the catalyst achieves a low overpotential of -0.354 V at 10 mA cm^-2 and a small Tafel slope of 53.9 mV dec^-1, surpassing its individual components. This work offers strategic guidance for designing highly efficient non-noble metal HER electrocatalysts via interface engineering and electronic structure tuning.