Enhancing the Performance of a Robust Sol–Gel‐Processed p‐Type Delafossite CuFeO₂ Photocathode for Solar Water Reduction

Abstract

Delafossite CuFeO2 is a promising material for solar hydrogen production, but is limited by poor photocurrent. Strategies are demonstrated herein to improve the performance of CuFeO2 electrodes prepared directly on transparent conductive substrates by using a simple sol-gel technique. Optimizing the delafossite layer thickness and increasing the majority carrier concentration (through the thermal intercalation of oxygen) give insights into the limitations of photogenerated charge extraction and enable performance improvements. In oxygen-saturated electrolyte, (sacrificial) photocurrents (1 sun illumination) up to 1.51 mA cm(-2) at +0.35 V versus a reversible hydrogen electrode (RHE) are observed. Water photoreduction with bare delafossite is limited by poor hydrogen evolution catalysis, but employing methyl viologen as an electron acceptor verifies that photogenerated electrons can be extracted from the conduction band before recombination into mid-gap trap states identified by electrochemical impedance spectroscopy. Through the use of suitable oxide overlayers and a platinum catalyst, sustained solar hydrogen production photocurrents of 0.4 mA cm(-2) at 0 V versus RHE (0.8 mA cm(-2) at -0.2 V) are demonstrated. Importantly, bare CuFeO2 is highly stable at potentials at which photocurrent is generated. No degradation is observed after 40 h under operating conditions in oxygen-saturated electrolyte.

Copper ferrites@reduced graphene oxide anode materials for advanced lithium storage applications

“…2b). There are three modes at around 105, 342 and 670 cm −1 , which correspond to E u , E g and A 1 g of delafossite CuFeO 2 56 . In addition, two well-resolved bands at 1360 and 1590 cm −1 for CuFeO 2 @rGO are attributed to the D band (k-point phonon of A 1 g symmetry) and G band (E 2 g phonon of carbon) of graphene, respectively.…”

A Bottom‐Up Approach toward All‐Solution‐Processed High‐Efficiency Cu(In,Ga)S2 Photocathodes for Solar Water Splitting

“…For chopped-light linear sweep voltammograms a scan rate of 8 mV s -1 , and a 500 W Muller Electronik Xenon-arc lamp, calibrated to provide 1 sun (AM 1.5G, 100 mW cm -2 ) were used. [ 81 ] In all cases the electrodes were front-illuminated (electrolyte side), since the use of Mo foil as substrate prevents back illumination. In all the measurements, the applied potentials are referred to the reversible hydrogen electrode (RHE) for the sake of comparison with other reports.…”

Templating Sol–Gel Hematite Films with Sacrificial Copper Oxide: Enhancing Photoanode Performance with Nanostructure and Oxygen Vacancies

“…22 The copper-iron oxide was prepared by successively spin-coating a solution containing iron oxide and copper oxide precursors that, were sequentially annealed at 450 °C to create an intimate mixture of the oxides and finally annealed under oxygen-deficient atmosphere at 700 °C to synthesize the delafossite structure. In an attempt to enhance the crystallinity of the copper-iron oxide, the sample was dipped in a saturated solution of NaCl prior the last thermal treatment.…”