Figure 4.

Non-noble metal SACs with external Co SAs

(A) HAADF-STEM image of the Co-NG catalyst with the scale bar of 1 nm.

(B) Percentages of Co, N, O, and C in the Co-NG catalyst measured by XPS and ICP-OES.

(C) The k²-weighted EXAFS in k-space for Co-NG and Co-G.

(D) LSVs of NG, Co-G, Co-NG, and Pt/C in 0.5 M H₂SO₄ at the scan rate of 2 mV s⁻¹.

(E) The molar number of produced H₂ as a function of time, where the red line denotes the theoretically calculated amounts of H₂ with 100% Faradaic efficiency.

(F) LSV polarization curves for catalysts with the Co loading of 0.03 (Co-NG1), 0.09 (Co-NG2), 0.29 (Co-NG3), 0.57 (Co-NG4), and 1.23 (Co-NG5).

(A–F) Reproduced with permission.⁸¹ Copyright 2015, Nature Publishing Group.