Cobalt-doping mediated low-valence Rh centers in rhodium sulfide superconductor for improved electrocatalytic hydrogen evolution

Abstract

Doping is an effective strategy to boost the hydrogen evolution reaction (HER) performance. Here, we construct a Co-doping Rh₁₇S₁₅ electrocatalyst fabricated using a green method, avoiding the use of any organic solvent. These fabricated electrocatalysts exhibit superior HER activity both in acidic and alkaline media. In 0.5 M H₂SO₄ electrolyte, Rh_16.85Co_0.15S₁₅ has an apparent overpotential and Tafel slope decrease of 135.8 mV and 46.2 mV dec^-1 compared with Rh₁₇S₁₅. Besides, the electrochemical active surface area (ECSA) of Rh_16.85Co_0.15S₁₅ is around 5.0 times that of Rh₁₇S₁₅. While in 1 M KOH electrolyte, the Rh_16.85Co_0.15S₁₅ also exhibits the most outstanding HER activity with an evident overpotential, Tafel slope, and R_ct declining of 78.9 mV, 78.4 mV dec^-1 and 13.6 Ω compared with Rh₁₇S₁₅. Moreover, the ECSA of Rh_16.85Co_0.15S₁₅ is 1.7 times that of Rh₁₇S₁₅. Although the low values are a little far from the commercial Pt/C (20%) of 46.8 mV in an acidic medium, these low values are close to the commercial Pt/C (20%) of 62.8 mV in an alkaline medium. First-principles calculations show that Co-doping decreases the reaction energy barrier and thus improves the electrocatalysis performance of Co-doping Rh₁₇S₁₅. Beyond offering an advanced electrocatalyst in different media, this work guides the designing and tuning properties of electrocatalysts.