# Electronic Structure and Interfacial Hole Transfer in a Di-Rhodium Photocatalyst on a p‑Type NiO Electrode

## TL;DR

This paper studies how a dirhodium complex interacts with a NiO electrode to improve solar-driven hydrogen production.

## Contribution

The study introduces a transferable hybrid-DFT/POD approach to analyze interfacial hole transfer in photocatalytic systems.

## Key findings

- DiRh binds strongly to NiO through mono- or bi-anchored configurations with minimal impact on its intrinsic properties.
- The monoanchored s-DiRh/NiO interface shows stronger coupling to NiO's valence band and reduced charge recombination.
- The hybrid-DFT/POD approach provides predictive insights into electronic structures and charge transfer at electrode-molecule interfaces.

## Abstract

Dye-sensitized photoelectrochemical cells are a promising
route
for solar-driven hydrogen production, using molecular dyes to generate
electron–hole pairs that drive electrochemical reactions. A
key challenge is achieving efficient charge transfer among the sensitizer,
electrode, and catalyst. Paddlewheel dirhodium (DiRh) complexes have
recently emerged as effective single-molecule photocatalysts, showing
high activity when anchored to nickel oxide (NiO) electrodes for hydrogen
evolution under red light. Here, we employ density functional theory
(DFT) and projection-operator diabatization (POD) analysis to investigate
the electronic structure of DiRh, its interaction with NiO, and the
mechanisms of interfacial hole transfer. Our results show that DiRh
binds strongly to NiO through stable mono- or bi- anchored configurations,
with distinct ligand contributions to the charge-transfer pathway.
While anchoring improves charge-separation efficiency, it has a minimal
impact on the intrinsic properties of DiRh. Notably, the monoanchored
s-DiRh/NiO interface exhibits stronger coupling to the NiO valence
band and reduced charge recombination, making it the most favorable
configuration for rapid hole injection. These findings provide atomistic
insight into the structure–function relationships at dye–catalyst/electrode
interfaces, offering design guidelines for next-generation photoelectrochemical
systems for renewable hydrogen production. Beyond this case study,
our work validates the use of a transferable hybrid-DFT/POD approach
for realistic electrode–molecule systems, providing predictive
atomistic insight into their interfacial electronic structure and
charge-transfer characteristics.