  Unraveling a descriptor that is correlated with catalytic reactivity is
essential for fast screening for the optimal catalysts for a given catalytic
reaction. Herein, we propose bond-derived orbitalwise coordination number
($\overline{CN}^\alpha$, $\alpha$= $s$ or $d$) as a simple and accurate
descriptor used for transition metal (TM) oxides that takes into account both
geometrical and electronic structures around active sites, and avoids excessive
computation burden. This descriptor has a strong scaling relation with the
activity in oxygen electrochemistry, enabling us to readily screen for the
optimal catalyst for $\beta$-MnO$_2$. $\beta$-MnO$_2$ with
$\overline{CN}^\alpha$=5.6 by creating an oxygen vacancy on (110) surface
exhibits the best oxygen electrochemical activity, which is well consistent
with experimetal result. This descriptor can be universally applied to other TM
oxides, e.g. RuO$_2$, opening up a new route as a guideline to design novel
catalysts in catalytic reactions.
