Abstract
ABSTRACT
Photocatalytic water splitting for H
2
generation represents a promising pathway for converting solar energy into clean chemical fuels, yet the efficiency is often limited by sluggish charge separation and inadequate utilization of photogenerated carriers. Here, we rationally design a novel p−n heterojunction photocatalyst composed of shape‐controlled Co
3
O
4
nanocrystals (nanocubes, nanoplatelets, and nanorods) coupled with Zn
2
InS
4
nanosheets for enhanced photocatalytic H
2
evolution. Among these, Co
3
O
4
nanocubes exhibit the highest H
2
evolution activity when integrated with Zn
2
InS
4
. Systematic characterization reveals that the heterojunction interface generates a robust built‐in internal electric field (IEF) through via controlled engineering of facet heterojunctions, which strongly drives the separation and migration of electron−hole pairs. In situ X‐ray photoelectron spectroscopy, femtosecond‐to‐microsecond transient spectroscopy, and theoretical calculations provide the direct evidence for a new Type‑I charge‐transfer pathway with significantly prolonged carrier lifetimes. The optimal Co
3
O
4
/Zn
2
InS
4
heterojunction achieves a remarkable H
2
evolution rate of 8570 µmol h
−1
g
−1
and excellent stability under visible‐light irradiation—an 11‑fold improvement over pristine Zn
2
InS
4
—with an apparent quantum yield of 9.5% at 420 nm. This work underscores the pivotal role of Co
3
O
4
morphology in tuning interfacial properties and offers a generalizable, noble‐metal‐free strategy for developing high‐performance p−n heterojunction photocatalysts for sustainable H
2
production and beyond.