How to add origin (0,0) to a plot?

I have the following code for a plot.

\documentclass[]{article}
\usepackage{tikz, pgfplots}
\begin{document}
\begin{figure}[h]
\centering
\begin{tikzpicture}
\begin{axis}[
xlabel=$w_{jk}^*$,
ylabel={$\frac{\partial U_i^*}{\partial l_i}$},
xtick={0,0.1,0.2},
domain=0:.2,
samples=20,
xmin=0.02,
xmax=0.23,
ymin=-43,
ymax=-39
]

• Hi and Welcome to TeX.SX! Why have you set the axis limits to these values? A node at (0,0) will be outside of the current plot window due to the axis limits. That being said, you can use something like \node [below left] at (axis cs:0,0) {(0,0)}; to add a node at the axis coordinates (0,0) – Grimler Oct 10 '17 at 13:47
• Off-Topic: You always should set option compat asap after loading pgfplots. See the pgfplots manual for more information. – Schweinebacke Oct 10 '17 at 14:17