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In order to develop water splitting as a sustainable technology, cost-effective and green electrocatalysts are urgently needed. We report a fabrication of an efficient self-supported whole-carbon electrocatalyst for overall water splitting in a wide pH range, which consist of nitrogen-doped vertically aligned graphene arrays and nitrogen-doped carbon quantum dots (N-VG-CQDs) prepared from vinegar residue. N-VG-CQDs electrocatalyst displays excellent electrocatalytic performances towards hydrogen evolution reaction (overpotentials of 218 and 238 mV in 1.0 M KOH and 0.5 M H 2 SO 4 , respectively), as well as outstanding performances towards oxygen evolution reaction (overpotentials of 383 and 497 mV in 1.0 M KOH and 0.5 M H 2 SO 4 , respectively). In addition, N-VG-CQDs acts as a self-supporting bifunctional electrocatalyst, exhibiting good stabilities in both acidic and alkaline electrolytes and an excellent Faraday efficiency (about 83 %). This study sheds light on the usage of vinegar residue towards the development of cost-effective whole-carbon electrocatalysts in water splitting. And the study also facilitates the use of environmental pollutions to prepare electrocatalysts for water splitting and advances the development of the water splitting industry. [Display omitted] • Vinegar residue is used as the carbon source to prepare carbon quantum dots. • Whole-carbon N-VG-CQDs catalyst is prepared by integrating N-CQDs with N-VG. • N-VG-CQDs shows an excellent utility in overall water-splitting with a wide pH range. [ABSTRACT FROM AUTHOR]

• A novel strategy has designed for the fabrication of efficient self-supported bifunctional electrocatalysts consist of vertically aligned boron doped graphene (B-VG) integrated with different compositions of iron-based metal borides nanoparticles (IMBs@B-VG) for overall water splitting. • Ternary iron-based metal borides exhibited enhanced catalytic activity compared with monometallic and bimetallic borides. • FeCoNiB@B-VG exhibited excellent electrocatalytic activity for overall water splitting in a wide pH range, especially in alkaline conditions. The development of efficient, cost-effective, bifunctional and self-supported electrocatalysts for overall water splitting in a wide pH range is highly desirable. A novel and highly efficient electrocatalyst for overall water splitting in a wide pH range was synthesized via the electroless plating of FeCoNiB alloy nanoparticles on B-doped vertically aligned graphene arrays (FeCoNiB@B-VG). FeCoNiB@B-VG exhibited excellent electrocatalytic performances with a low overpotential of 31 mV in 1.0 M KOH and 148 mV in 0.5 M H 2 SO 4 for hydrogen evolution reaction (HER), and an overpotential of 387 mV in 1.0 M KOH for oxygen evolution reaction (OER). It also exhibited a quite low Tafel slope value of 30 mV dec−1 and 51 mV dec−1 for HER and OER in 1.0 M KOH respectively. In addition, FeCoNiB@B-VG also exhibited good long-term stabilities in acidic and alkaline electrolytes as a self-supported bifunctional electrocatalyst. This work may provide theoretical and technical support for design of cost-effective bifunctional electrocatalysts for overall water splitting in a wide pH range. [Display omitted] [ABSTRACT FROM AUTHOR]