To illustrate which additions of Sn and/or Ti improve upon the Mn-Sb-O baseline, Fig. shows the same set of data as Fig. with a series of pseudo-ternary Sb-Sn-Ti compositions plots corresponding to Mn concentration bins: below 0.4, between 0.4 and 0.6, and between 0.6 and 0.8. Graphically, this corresponds to projecting the points within the composition tetrahedron of Fig. to the Sb-Sn-Ti composition triangle, which projects all Mn-Sb-O baseline compositions to the 100% Sb corner of each composition triangle. With this plotting scheme, the goal of improving activity through addition of Sn and/or Ti corresponds to achieving higher activity on the Sb-Sn edge, on the Sb-Ti edge, or within the Sb-Sn-Ti region of each composition plot. Fig. shows that this goal is achieved within each of the 3 ranges of Mn concentration (each panel contains points larger than the largest point at the bottom-right corner).