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[Display omitted] • A new graphdiyne based metal-free catalyst was successfully synthesized. • The catalyst triggered highly catalytic performances toward hydrogen evolution. • The unique nanostructure guaranteed the fast proton-electron transfer during HER. • The alkyne-alkene transition induced the excellent catalytic activity of TAGDY. Graphdiyne-based metal-free catalysts demonstrate outstanding performances in electrocatalysis. In order to accurately understand the activity origin of metal-free electrocatalytic hydrogen production at the atomic level, we have successfully designed and prepared a new metal-free catalyst of 1,2,4-triamino-graphdiyne (TAGDY). Structural characterizations showed that TAGDY has unique nanostructure, which guarantees the fast proton-electron transfer during the catalytic process. Experimental studies revealed that TAGDY possesses excellent electrocatalytic activities and long-term durability towards hydrogen evolution in acidic conditions, better than the most reported metal-free electrocatalysts. Density functional theory calculations and Born-Oppenheimer molecular dynamics simulations revealed that the interaction of (H++e−) pair with alkyne bond induces the transition between C C and C C in TAGDY, which effectively enhanced the catalytic activities of initial inert carbon sites. Combination of theory and experiment as well as the structural characterization, a new level of knowledge for the activity origin and catalytic mechanism of graphdiyne-based metal-free electrocatalysts are presented. [ABSTRACT FROM AUTHOR]

• We simultaneously introduce P doping and Se vacancies in NiSe 2 nanosheets. • The synergistic effects of P doping and Se vacancies promote HER activities. • DFT results demonstrate the lower Gibbs free energy of adsorbed H* in A-NiSe 2 |P. • A low voltage of 1.62 V is achieved at 10 mA cm−2 for overall water splitting. Element doping is a general and effective approach to modify the electrocatalytic performances, but the low intrinsic activity in each electroactive site still limits the further improvements. Herein, we provide an effective strategy by simultaneously introducing P doping and Se vacancies to enhance the intrinsic activities in NiSe 2 nanosheet arrays (A-NiSe 2 |P) through Ar plasma treatment. Owing to the increased active sites and enhanced electrical conductivity, the resulted A-NiSe 2 |P shows the enhanced hydrogen evolution performances. Theoretical calculations reveal that introduction of Se vacancies plays a significant role in lowering the adsorption free energy of H* in Ni, Se and P sites, leading to promoted intrinsic activities in A-NiSe 2 |P. Further, A-NiSe 2 |P as bifunctional electrocatalysts only needs 1.62 V to reach 10 mA cm−2 for overall water splitting. Our study and understanding of A-NiSe 2 |P may highlight the importance of element doping and vacancies in enhancing the catalytic activities in overall water splitting. [ABSTRACT FROM AUTHOR]