Modulating electronic structures of holey Mo2N nanobelts by sulfur decoration for enhanced hydrogen generation.

• The electronic structures of holey Mo 2 N nanobelts are modulated by sulfur decoration. • The enhanced activity is originated from the optimized hydrogen binding energy. • The stability of oxygen-sensitive Mo 2 N is significantly improved. • A small Tafel slope of 39 mV dec−1 is achieved in acidic media. As one of the candidates to replace noble Pt-based catalysts, low-cost Mo 2 N with rich abundance has attracted much attention in catalyzing the hydrogen evolution reaction (HER) due to the similar electronic structures to Pt. However, Mo 2 N possesses a strong hydrogen binding ability and is highly sensitive to the oxygen, resulting in limited kinetics associated with deteriorated HER performances. Herein, a sulfur decoration strategy is presented to modulate the electronic structures and surface compositions, so that an optimized hydrogen adsorption free energy and protective sulfide shell can be obtained, leading to significant enhancement of performance with a small Tafel slope of 39 mV dec−1 in acidic media, outperforming the vast majority of reported non-precious metal electrocatalysts for the HER. Moreover, the improvement mechanisms and composition evolution have also been investigated. And the first-principle calculation is provided to give a theoretic evidence for the modulation of corresponding electronic structures. This work verifies that the rational decoration with a second anion is a powerful and effective strategy to design highly active and durable HER electrocatalysts, further demonstrating the importance of anions for the HER. [ABSTRACT FROM AUTHOR]