Copper Oxide-Based Photocatalysts and Photocathodes: Fundamentals and Recent Advances

Abstract

This work aims at reviewing the most impactful results obtained on the development of Cu-based photocathodes. The need of a sustainable exploitation of renewable energy sources and the parallel request of reducing pollutant emissions in airborne streams and in waters call for new technologies based on the use of efficient, abundant, low-toxicity and low-cost materials. Photoelectrochemical devices that adopts abundant element-based photoelectrodes might respond to these requests being an enabling technology for the direct use of sunlight to the production of energy fuels form water electrolysis (H2) and CO2 reduction (to alcohols, light hydrocarbons), as well as for the degradation of pollutants. This review analyses the physical chemical properties of Cu2O (and CuO) and the possible strategies to tune them (doping, lattice strain). Combining Cu with other elements in multinary oxides or in composite photoelectrodes is also discussed in detail. Finally, a short overview on the possible applications of these materials is presented.

Evaluation of the Efficiency of Photoelectrochemical Activity Enhancement for the Nanostructured LaFeO3 Photocathode by Surface Passivation and Co-Catalyst Deposition

“…Films of LFO on fluorine-doped tin oxide (FTO) substrates were fabricated using a modified procedure from ref. [ 21 ]. Briefly, 0.2 g of La(NO 3 ) 3 *6H 2 O, 0.19 g Fe(NO 3 ) 3 *9H 2 O and 0.38 g of citric acid monohydrate were dissolved in 0.5 mL of deionized water under magnetic stirring at room temperature.…”

“…Most of the TMO-based materials, which were extensively studied in photoelectrochemical processes, are photoanodes [ 1 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] (TiO 2 , Fe 2 O 3 , BiVO 4 , SrTiO 3 ), while much less attention has been paid to metal oxide photocathodes [ 17 , 18 , 19 ], except for copper-based materials. Copper-based photocathodes [ 20 ], such as Cu 2 O and CuBi 2 O 4 , show attractive activity in photoelectrochemical processes, yet their chemical and electrochemical stability under operating conditions remains a significant challenge [ 21 ] since successful application requires surface modification with protective coatings [ 22 ].…”

Plasmon‐Assisted Operando Self‐Healing of Cu2O Photocathodes

“…[ 7 ] To overcome this bottleneck, scientists have developed several strategies to preserve the Cu 2 O integrity, by stabilizing the surface through deposition of conformal coatings or employing passivating agents. [ 1 ] Several examples of these approaches are present in the literature, and here we only mention a few of them. First, we recall the pioneering work of Thimsen and coworkers, in which atomic layer deposition (ALD) was employed to deposit ultrathin layers of titania, zinc oxide, and alumina on electrodeposited Cu 2 O, achieving up to 7.6 mA cm −2 photocurrent under AM 1.5 illumination at a potential of 0 V versus the reversible hydrogen electrode at mild pH.…”

“…Cuprous oxide (Cu 2 O) is one of the most interesting p-type metal oxide semiconductors, suitable to act as active material for photocathodes in photoelectrochemical (PEC) hydrogen production from water splitting. [1,2] This interest mostly derives from its electronic properties: a suitable band gap for visible light absorption (2.2-2.4 eV) and band positions allowing both hydrogen (HER) and oxygen evolution reaction (OER), the former being the most pursued one. [3] In addition, there is also a relevant economical motivation for deepening our knowledge about this material.…”

Understanding the Role of Copper Vacancies in Photoelectrochemical CO2 Reduction on Cuprous Oxide

“…Calculated values for hole density by M-S analysis (Table S1) confirm the observed trend for copper vacancies. Hole density values are in the order of 10 19 cm –3 , while copper vacancy density can be of an order of magnitude higher because only a fraction of the vacancies will release holes to the valence band. , To reveal the copper vacancy effect on PEC activity, we investigate the CO 2 reduction properties of copper vacancy modulated Cu 2 O photocathodes. We chose to study PEC energy conversion in a CO 2 -saturated 0.1 M Na 2 SO 4 solution at pH 4.2 (ion strength 0.3), where the predominant species is CO 2 (Figure S9).…”