Electrochemical Growth of Copper Hydroxy Double Salt Films and Their Conversion to Nanostructured p-Type CuO Photocathodes

Abstract

New electrochemical synthesis methods were developed to produce copper hydroxy double salt(Cu-HDS) films with four different intercalated anions (NO, SO, Cl, and dodecyl sulfate (DS)) as pure crystalline films as deposited (CuNO(OH), CuSO(OH), CuCl(OH), and CuDS(OH)). These methods are based on p-benzoquinone reduction, which increases the local pH at the working electrode and triggers the precipitation of Cu and appropriate anions as Cu-HDS films on the working electrode. The resulting Cu-HDS films could be converted to crystalline Cu(OH) and CuO films by immersing them in basic solutions. Because Cu-HDS films were composed of 2D crystals as a result of the atomic-level layered structure of HDS, the CuO films prepared from Cu-HDS films have unique low-dimensional nanostructures, creating high surface areas that cannot be obtained by direct deposition of CuO, which has a 3D atomic-level crystal structure. The resulting nanostructures allowed the CuO films to facilitate electron-hole separation and demonstrate great promise for photocurrent generation when investigated as a photocathode for a water-splitting photoelectrochemical cell. Electrochemical synthesis of Cu-HDS films and their facile conversion to CuO films will provide new routes to tune the morphologies and properties of the CuO electrodes that may not be possible by other synthesis means.

Mechanistic insights of enhanced spin polaron conduction in CuO through atomic doping

“…Previously, we have demonstrated that nanofibrous CuO electrodes can be prepared by using electrodeposited Cu 4 SO 4 (OH) 6 films as precursors. 54 The electrodeposited Cu 4 SO 4 (OH) 6 films are composed of blade-like nanocrystals due to the two dimensional crystal structure of Cu 4 SO 4 (OH) 6 ( Figure S14A). When immersed in 0.01 M NaOH solution (pH 12), they were converted to fibrous Cu(OH) 2 films ( Figure S14B), which could be converted to fibrous CuO films by annealing for 3 h at 500°C.…”

“…In this study, we used oxygen reduction as the photoelectrochemical reduction reaction that occurs on the CuO surface as the kinetics of this reaction is typically much faster than water reduction on oxide-based photocathodes. [54][55][56][57] The J−V plots of CuO and Li-doped CuO for oxygen reduction obtained in a 0.1 M KOH (pH 13) solution purged with O 2 under standard illumination conditions (AM1.5G, 100 mW/cm 2 ) are shown in Fig. 5.…”

Porous Cupric Oxide: Efficient Photocathode for Photoelectrochemical Water Splitting

“…Cardiel et al. synthesized CuO nanostructure from 2D Cu‐hydroxy double salt precursor which can generate photocurrent density of ∼1.5 mA/cm 2 at an applied potential of 0.6 V vs. RHE …”

An investigation of photovoltaic devices based onp‐typeCu2Oandn‐typeγ‐WO3junction through an electrolyte solution containing a redox pair

“…Figure 4(iv) displays a typical thickness of 600 nm for γ‐WO 3 films. A possibly useful strategy is the so‐called nanostructuring, which can shorten the necessary traveling distance of minority carriers so that they reach the interface and consequently minimize the electron‐hole recombination 73 …”