Abstract <p>Liquid-phase synthesis of rhodium by the hydrosol method was carried out using formic acid as a reducing agent, both in the presence of a catalyst support and without it. Transmission electron microscopy combined with dynamic light scattering demonstrated stabilization of rhodium particles on the support surface and the formation of a narrow size distribution of rhodium nanoparticles, approximately 80% with sizes of 1–2 nm, uniformly distributed on the support with a modified surface. Polarization curves of the Rh/C catalyst were measured using a stationary glassy carbon disk electrode for the hydrogen evolution reaction at 60°C in 0.5 M H₂SO₄. The observed decrease in charge and specific surface area of the electrocatalyst under reaction conditions compared with the initial state may be attributed to interaction of catalytically active nanodispersed rhodium with carbon black, which also exhibits catalytic activity, during measurement of the polarization curves.</p>