  Spherical colloids that catalyze the interconversion reaction $A
\leftrightharpoons B$ between solute molecules $A$ and $B$ whose concentration
at infinity is maintained away from equilibrium effectively interact due to the
non-uniform fields of solute concentrations. We show that this long range $1/r$
interaction is suppressed via a mechanism that is superficially reminiscent but
qualitatively very different from electrostatic screening: catalytic activity
drives the concentrations of solute molecules towards their equilibrium values
and reduces the chemical imbalance that drives the interaction between the
colloids. The imposed non-equilibrium boundary conditions give rise to a
variety of geometry-dependent scenarios; while long-range interactions are
suppressed (except for a finite penetration depth) in the bulk of the colloid
solution in 3D, they can persist in quasi-2D geometry in which the colloids but
not the solutes are confined to a surface, resulting in the formation of
clusters or Wigner crystals, depending on the sign of the interaction between
colloids.
