# Hybrid PEDOT Conductive Polymer-Powdered Metal Sulfide Photocathodes for Photoelectrochemical Green H2 Production

## TL;DR

This paper introduces a new hybrid photocathode material that boosts hydrogen production efficiency using a simple method for green energy applications.

## Contribution

The novel hybrid photocathode combines metal sulfide powders with PEDOT to achieve high performance in photoelectrochemical H2 production.

## Key findings

- PEDOT modification increased the photocurrent density of (CuGa)0.5ZnS2 by 60 times under visible light.
- The hybrid photocathode achieved 30% IPCE at 420 nm for H2 evolution.
- Solar water splitting occurred without external bias using the hybrid photocathode and BiVO4 photoanode.

## Abstract

Hybrid photocathodes combining metal sulfide powders
with poly-3,4-ethylenedioxythiophene
(PEDOT) as an effective hole transporting polymer were prepared through
a facile drop-casting method and electrochemically oxidative polymerization
of 3,4-ethylenedioxythiophene (EDOT). The PEDOT modification remarkably
enhanced a photocurrent density of a powder-based (CuGa)0.5ZnS2 photocathode (bandgap (BG): 2.3 eV) for hydrogen
evolution under visible light irradiation at 0 V vs RHE, 60-times
higher compared with an unmodified photocathode. The improvement was
advantageously effective when using small metal sulfide particles
prepared by a flux method compared to large particles synthesized
by a solid-state reaction due to improved necking and interfacial
contact facilitated by PEDOT in the fine physical structure. The optimized
PEDOT/(CuGa)0.5ZnS2-composited photocathode
(PEDOT-(CuGa)0.5ZnS2) achieved an incident photon-to-current
conversion efficiency (IPCE) of 30% at 420 nm and 0 V vs RHE for the
H2 evolution. PEDOT modification was also effective for
Cu2ZnSnS4 (BG: 1.4 eV) and Cu3VS4 (BG: 1.5 eV) black metal sulfide photocathodes. Furthermore,
solar water splitting proceeded in a two-electrode photoelectrochemical
cell consisting of a PEDOT-(CuGa)0.5ZnS2 photocathode
and a BiVO4-based photoanode, even without applying an
external bias. The photoelectrochemical cell gave 0.08% for nonbias
and 0.21% for 0.4 V of an external bias of a solar-to-hydrogen energy
conversion efficiency (STH), even though both photoelectrodes were
fabricated without any vacuum process and using just two ingredients.
Our findings will offer a viable strategy for developing photocathodes
that unite simplicity and high performance by using powder materials
for the scalable application of photoelectrochemical green H2 production.