Highly dispersed ultrafine Ru nanoparticles on a honeycomb-like N-doped carbon matrix with modified rectifying contact for enhanced electrochemical hydrogen evolution.

The manipulation of rectifying contact between metal and semiconductor represents a powerful strategy to modify the electronic configuration of active sites for improved electrocatalytic performance. Herein, we present an NaCl template-assisted approach to rationally construct a Schottky electrocatalyst consisting of a honeycomb-like N-doped carbon matrix decorated with uniformly ultrasmall Ru nanoparticles with an average diameter of 2.5 nm (hereafter abbreviated as Ru NPs@HNC). It is found that the Fermi level difference between Ru and HNC can cause self-driven migration of electrons from Ru NPs to the HNC substrate, which leads to the generation of a built-in electric field and directional flow of electrons, thereby enhancing the intrinsic activity. In addition, the immobilization of ultrafine Ru NPs on the honeycomb-like carbon skeleton can effectively inhibit the undesired migration, agglomeration and detachment of the active sites, thus ensuring remarkable structural stability. As a result, the Ru NPs@HNC with optimal rectifying contact delivers superior electrochemical activity with a small overpotential of 28 mV at 10 mA cm and outstanding long-term stability in an alkaline solution. The design philosophy of grain-size modulation and Schottky contact may widen up insight into the preparation of high-performance electrocatalysts in sustainable energy conversion systems.