Density Functional Theory Studies of Doping and Curvature Effects on the Electrocatalytic Hydrogen Evolution Activity of Carbon Nanotubes

Using low-cost, efficient, and stable nonprecious alternatives for Pt-based catalysts is important for electrocatalytic hydrogen evolution reaction (HER), and carbon nanotubes (CNTs) with atom doping have shown great potential in electrocatalytic HER. In this work, we have systematically investigated the HER catalytic activities for a series of different curvature CNT (n,n) (n = 5–9), doped with atomic N or N and Co via the first-principle computation. The computed results indicate that H binding capability increases with the curvature increase for the CNTs and N-CNTs. Through manipulating the number of N atoms and the curvature, the N-CNTs can exhibit the optimal considerable ΔGH* values and can be used as an HER catalyst comparable to metal Pt. Moreover, the hydrogen adsorption/desorption can be balanced through the Co atom doped inside the mNy-CNT (n,n) systems because of the charge transfer. The Co/1N-CNT (8,8), Co/1N-CNT (9,9), Co/2No-CNT (9,9), and Co/2Np-CNT (9,9) revealed the ideal HER activity, which could be a promising catalyst for hydrogen production. Meanwhile, the strength of the H adsorption energy of the systems can be correlated to the C pz band center. Thus, the HER catalytic activity of CNT (n,n) (n = 5–9) can be reasonably regulated through doping atoms and designing low-cost and high-performance carbon-based electrocatalysts.