chemical reactions

Question

I would like to reproduce the same as this picture using the chemfig package:

\documentclass[french,12pt,oneside,openright]{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[a4paper]{geometry}
\usepackage[french]{babel} %langue francaise
\usepackage{graphicx,xcolor} %insertion d'images
\usepackage{titlesec}
\graphicspath{{Annexes/images/}} %directory of the images
\usepackage{lipsum} %paragraphes prédéfinis
%\usepackage{fancyhdr} %decoration des en tetes
\usepackage[sonny]{fncychap}
\usepackage{usnomencl}%pour la nomenclature
\usepackage{pgfplots}
\usepackage{chemmacros}
\usepackage{chemfig}
\renewcommand*\printatom[1]{\ensuremath{\mathsf{#1}}}

\begin{document}
\setchemrel{1pt}{}{6em}
\textbf{Sc\chemrel[\footnotesize hnu]{<->}e$^{-}_{CB}$ \chemsign+ h$^{+}_{VB}$}\\
\setchemrel{1pt}{}{6em}
\textbf{A$_{ads}$\chemsign+ e$^{-}_{CB}$ \chemrel[\footnotesize hnu]{->}A$^{{•}-}_{ads}$}\\

\end{document}

Answer 1

I'm not sure why you want to typeset the reactions with chemfig. It is an excellent package for drawing skeletal formulae of organic compounds. However, the reactions in your example are much easier typeset with mhchem or chemformula. The latter is loaded by chemmacros so you already have it available.

\documentclass{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}

\usepackage{chemformula}

\begin{document}

\begin{center}
  \setchemformula{charge-hshift=0pt}
  % \sffamily % uncomment if you want or need the following to be sans serif
  \ch{ Sc ->[$h\nu$] e_{CB}- + h_{VB}+} \\[1ex]
  \ch{A_{ads} + e_{CB}- -> @{charge-hshift=-.15em} A_{ads}^{*-}} \\[1ex]
  \ch{D_{ads} + h_{VB}^+ -> D_{ads}^{*+}}
\end{center}

\end{document}

Anyway, if you insist on using chemfig you should read what it writes in the log file and follow the advice:

Package chemfig Warning: the macro \chemrel is deprecated. Please, build schemes with \schemestart and inside, use \arrow.

\documentclass{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}

\usepackage{chemfig}
\usepackage{amsmath}% for \text

\begin{document}

\begin{center}
  \schemestart
    Sc
    \arrow{->[$h\nu$]}
    $\mathrm{e}_{\text{CB}}^- + \mathrm{h}_{\text{VB}}^+$
  \schemestop\\[1ex]
  \schemestart
    $\mathrm{A}_{\text{ads}} + \mathrm{e}_{\text{CB}}^-$
    \arrow
    $\mathrm{A}_{\text{ads}}^{*-}$
  \schemestop\\[1ex]
  \schemestart
    $\mathrm{D}_{\text{ads}} + \mathrm{h}_{\text{VB}}^+$
    \arrow
    $\mathrm{D}_{\text{ads}}^{*+}$
  \schemestop
\end{center}

\end{document}

Using sans serif font for the reactions is possible and for the chemformula version only requires to set the surrounding text font to sans serif. In the chemfig version it requires a little bit more work.