Carbon Dots Strongly Immobilized onto Carbon Nanohorns as Non‐Metal Heterostructure with High Electrocatalytic Activity towards Protons Reduction in Hydrogen Evolution Reaction

Abstract Highly performing, non‐metal inexpensive electrocatalysts for the production of hydrogen via electrochemical water splitting are called for the replacement of current platinum‐based ones. In order to speed up the electrocatalytic hydrogen evolution, abundant active sites but also efficient charge transfer is needed. In this context, 0D carbon dots (CDs) with large specific surface area, low cost, high conductivity, and rich functional groups emerge as promising non‐metal electrocatalysts. Additionally, the use of conductive substrates provides an effective strategy to boost their electrocatalytic performance. Herein, the unique 3D superstructure of carbon nanohorns (CNHs), as well as without any metal content in their structure, is used to provide a conductive support of high porosity, large specific surface area, and good electrical conductivity, for the in situ growth and immobilization of CDs, via a simple hydrothermal method. The direct contact of CDs with the 3D conductive network of CNHs promotes charge transfer, accelerating hydrogen evolution. The all‐carbon non‐metal CDs/CNHs nanoensembleshows an onset potential close to the one of Pt/C, low charge transfer resistance, and excellent stability.