Inverse Opal CuCrO2 Photocathodes for H2 Production Using Organic Dyes and a Molecular Ni Catalyst.

Charles E. Creissen,Yoann Farré,Daniel Antón-García,Erwin Reisner,Fabrice Odobel,Julien Warnan

doi:10.1021/acscatal.9b02984

Abstract

Dye-sensitized photoelectrochemical (DSPEC) cells are an emerging approach to producing solar fuels. The recent development of delafossite CuCrO2 as a p-type semiconductor has enabled H2 generation through the coassembly of catalyst and dye components. Here, we present a CuCrO2 electrode based on a high-surface-area inverse opal (IO) architecture with benchmark performance in DSPEC H2 generation. Coimmobilization of a phosphonated diketopyrrolopyrrole (DPP-P) or perylene monoimide (PMI-P) dye with a phosphonated molecular Ni catalyst (NiP) demonstrates the ability of IO-CuCrO2 to photogenerate H2. A positive photocurrent onset potential of approximately +0.8 V vs RHE was achieved with these photocathodes. The DPP-P-based photoelectrodes delivered photocurrents of −18 μA cm–2 and generated 160 ± 24 nmol of H2 cm–2, whereas the PMI-P-based photocathodes displayed higher photocurrents of −25 μA cm–2 and produced 215 ± 10 nmol of H2 cm–2 at 0.0 V vs RHE over the course of 2 h under visible light illumination (100 mW cm–2, AM 1.5G, λ > 420 nm, 25 °C). The high performance of the PMI-constructed system is attributed to the well-suited molecular structure and photophysical properties for p-type sensitization. These precious-metal-free photocathodes highlight the benefits of using bespoke IO-CuCrO2 electrodes as well as the important role of the molecular dye structure in DSPEC fuel synthesis.

Highlights

Solar conversion of water into chemical energy carriers offers a sustainable alternative to fossil fuels.[1−3] Dye-sensitized photoelectrochemical (DSPEC) cells featuring molecular catalysts are a promising technology for solar water splitting due to their engineering flexibility, easy modification, and assembly.[4−8] In these systems, semiconductor-immobilized molecular dyes harvest solar light and transfer charge to a catalytic site, facilitating the synthesis of solar fuels
Significant progress with dye-sensitized photocathodes (DSPCs) and photoanodes has been made possible through a deeper understanding of charge transfer processes and performance-limiting recombination routes.[9−18] efficiency has improved in recent years, DSPCs still suffer from low photocurrents and poor catalytic activity, representing a bottleneck in state of the art DSPEC devices
Transmission electron microscopy (TEM) analysis showed that crystalline particles of approximately 15 nm in length and 5 nm in diameter were obtained (Figure S1) with a Brunauer−Emmett−Teller (BET) surface area of 86 m2 g−1

Summary

Introduction

Solar conversion of water into chemical energy carriers offers a sustainable alternative to fossil fuels.[1−3] Dye-sensitized photoelectrochemical (DSPEC) cells featuring molecular catalysts are a promising technology for solar water splitting due to their engineering flexibility, easy modification, and assembly.[4−8] In these systems, semiconductor-immobilized molecular dyes harvest solar light and transfer charge to a catalytic site, facilitating the synthesis of solar fuels. Significant progress with dye-sensitized photocathodes (DSPCs) and photoanodes has been made possible through a deeper understanding of charge transfer processes and performance-limiting recombination routes.[9−18] efficiency has improved in recent years, DSPCs still suffer from low photocurrents and poor catalytic activity, representing a bottleneck in state of the art DSPEC devices. Higher photocurrents can be achieved by blocking the dominant recombination mechanisms between holes in the p-type semiconductor and (1) the reduced dye (geminate recombination) or (2) the reduced catalyst.[19−25]

Methods

Results

Conclusion