# Atomically Precise Cluster Cocatalysts: Missing Link toward Heterogenized Photocatalytic Systems

## TL;DR

This paper reviews how atomically precise clusters can act as efficient and stable cocatalysts for solar fuel production, bridging the gap between homogeneous and heterogeneous catalysis.

## Contribution

The paper introduces atomically precise clusters as a novel class of cocatalysts with tunable structures and enhanced stability for photocatalytic applications.

## Key findings

- Atomically precise clusters offer well-defined active sites and improved stability compared to nanoparticles or organometallic complexes.
- These clusters enable systematic studies of structure–activity relationships and provide mechanistic insights for catalyst design.
- Cluster-based cocatalysts show potential for multielectron redox processes and can be surface-anchored effectively.

## Abstract

This review critically examines the emerging role of
atomically
precise clusters – oxide, sulfide, and metallic in nature –
as transformative cocatalysts for photocatalytic solar fuel production.
Unlike structurally imprecise nanoparticles with ill-defined active
sites or molecular organometallic complexes with limited stability,
these clusters offer atomically resolved structures that bridge homogeneous
precision with heterogeneous robustness. Their well-defined multinuclear
architectures enable precise control over their active sites, facilitating
systematic studies of structure–activity relationships and
mechanistic insights critical to rational catalyst design. Compared
to contemporary cocatalytic systems, these clusters offer tunable
compositions and structures, enhanced stability on the surface, and
the capacity to engage in multielectron redox processes. We review
recent experimental developments, discuss strategies of their surface-anchoring,
and highlight mechanistic insights provided by their use. Finally,
we critically evaluate current challenges and propose future research
directions to unlock the full potential of cluster-based cocatalysts
as a tool for purposeful engineering of active and selective photocatalysts
for light-driven solar fuel generation.