Compound symbol for labeling thermodynamic cycles – a number inside a almost comple circle with an arrow tip. Drawn with tikz.

Circled-numbers-with-arrow.tex

% Requires tikz
% Requires calc
\usetikzlibrary{matrix,arrows,bending}

% TiKz arrowed circles, need to figure out how to differentiate H+ and e- cycles...
\makeatletter
\tikzset{%
   /qrr/circle arrow/.cd,
   start angle/.initial={},
   delta angle/.initial={},
   end angle/.initial={},
   arrows/.estore in=\qrr@ca@arrow,
   arrows=-
}

\pgfdeclareshape{circle arrow}{%
  \inheritsavedanchors[from=circle] \inheritanchorborder[from=circle]
  \inheritanchor[from=circle]{north}      \inheritanchor[from=circle]{north west}
  \inheritanchor[from=circle]{north east} \inheritanchor[from=circle]{center}
  \inheritanchor[from=circle]{west}       \inheritanchor[from=circle]{east}
  \inheritanchor[from=circle]{mid}        \inheritanchor[from=circle]{mid west}
  \inheritanchor[from=circle]{mid east}   \inheritanchor[from=circle]{base}
  \inheritanchor[from=circle]{base west}  \inheritanchor[from=circle]{base east}
  \inheritanchor[from=circle]{south}      \inheritanchor[from=circle]{south west}
  \inheritanchor[from=circle]{south east}
  \backgroundpath{
    \pgfkeysgetvalue{/qrr/circle arrow/start angle}\qrr@ca@s
    \pgfkeysgetvalue{/qrr/circle arrow/end angle}\qrr@ca@e
    \pgfkeysgetvalue{/qrr/circle arrow/delta angle}\qrr@ca@d
      \ifx\qrr@ca@s\pgfutil@empty%
        \pgfmathsetmacro\qrr@ca@s{\qrr@ca@e-\qrr@ca@d}%
      \else
        \ifx\qrr@ca@e\pgfutil@empty%
          \pgfmathsetmacro\qrr@ca@e{\qrr@ca@s+\qrr@ca@d}%
        \fi%
      \fi
    \pgfpathmoveto{\pgfpointadd{\centerpoint}{\pgfpointpolar{\qrr@ca@s}{\radius}}}%
    \pgfpatharc{\qrr@ca@s}{\qrr@ca@e}{\radius}%
    \pgfkeys{/tikz/arrows/.expand once=\qrr@ca@arrow}%
   }
}

\makeatother
\tikzset{% the first two styles are internal, they do not work alone!
  turn left/.style={/tikz/shape=circle arrow,/qrr/circle arrow/arrows=-{LaTeX[length=4pt,bend]},/qrr/circle arrow/delta angle=345},
  turn right/.style={/tikz/shape=circle arrow,/qrr/circle arrow/arrows={LaTeX[length=4pt,bend]}-,/qrr/circle arrow/delta angle=345},
  turn left north/.style  = {/tikz/turn left,  /qrr/circle arrow/start angle=100} ,
  turn left east/.style   = {/tikz/turn left,  /qrr/circle arrow/start angle=10},
  turn left south/.style  = {/tikz/turn left,  /qrr/circle arrow/start angle=280},
  turn left west/.style   = {/tikz/turn left,  /qrr/circle arrow/start angle=190},
  turn right north/.style = {/tikz/turn right, /qrr/circle arrow/start angle=100} ,
  turn right east/.style  = {/tikz/turn right, /qrr/circle arrow/start angle=10},
  turn right south/.style = {/tikz/turn right, /qrr/circle arrow/start angle=280},
  turn right west/.style  = {/tikz/turn right, /qrr/circle arrow/start angle=190},
}

\DeclareRobustCommand\circled[1]{\tikz[baseline=(char.base)]{%
  \node[turn left north, thick, draw, inner sep=0.1em] (char) {#1};
  }
}