Transparent Porous ZnO|Metal Complex Nanostructured Materials: Application to Electrocatalytic CO₂ Reduction

Abstract

We developed a simple and versatile approach for the electrochemical growth of hybrid ZnO|molecular catalyst nanostructured layers. Metal oxide|catalyst hybrid nanoporous layers with a sponge-like structure at the nanoscale and multiscale three-dimensional (3D) hierarchical structures based on nanoporous zinc oxide (ZnO) layers grown on ZnO nanorods were obtained. The thickness and structure of the hybrid nanoporous layers as well as the catalyst concentration can be tuned. This method allows the introduction of water-soluble molecular catalysts based on porphyrin and/or phthalocyanine derivatives into the ZnO matrix with a homogeneous distribution of the complex into the material. As an illustrative example, combining hybrid ZnO with a very low concentration of an encapsulated Co-based molecular catalyst inside the oxide layer results in a 97% catalytic response toward CO 2 reduction to CO with large currents in an organic solvent, highlighting the excellent electrocatalytic activities of such layers, which combine porosity, electronic conductivity, and synergetic properties from its components.

Constructing Highly Efficient ZnO Nanocatalysts with Exposed Extraordinary (110) Facet for CO2 Electroreduction

“…As shown in Figure a, the diffraction peaks detected at 2θ = 31.8, 34.4, 36.2, 47.5, 56.6, 62.9, and 68.0° correspond to the (100), (002), (101), (102), (110), (103) and (112) planes of ZnO, respectively . It can be observed that the positions of the diffraction peaks for all three samples were in precise accordance with the standard card of hexagonal wurtzite ZnO (JCPDS 36-1451) . No other impurity peaks were detected, demonstrating the high purity of the synthesized samples.…”

“…34 It can be observed that the positions of the diffraction peaks for all three samples were in precise accordance with the standard card of hexagonal wurtzite ZnO (JCPDS 36-1451). 40 No other impurity peaks were detected, demonstrating the high purity of the synthesized samples. The average crystallite sizes of the three samples were calculated by the Debye−Scherrer formula (D = 0.9 λ/β cos θ).…”

“…Notably, Zn-based catalysts have attracted much attention for CO 2 conversion due to their low cost, abundant reserves, and accessible CO selectivity, − which are considered as a promising alternative to noble metal catalysts. It was reported that ZnO nanosheets fabricated by adjusting alkaline additives and the molar ratios of zinc source/urea showed good CO 2 RR performance .…”

Multifunctional Photovoltaic Window Layers for Solar-Driven Catalytic Conversion of CO2: The Case of CIGS Solar Cells

“…A water-soluble tetracationic Co phthalocyanine complex (Figure S3) was encapsulated into the nanoporous ZnO layer during its photoelectrodeposition on the ZnO:Al window layer of the CIGS solar cells. The thickness of the ZnO|CoPcTA nanoporous (ZnO|CoPcTA NP) layer and the concentration of the catalyst could be controlled by adjusting the transferred charge during the ZnO growth process, as observed in Figure a . Increasing the charge from 0 to 4 C cm –2 results in a relatively linear increase in the ZnO|CoPcTA NP thickness up to 1200 nm.…”

“…To investigate the CO 2 reduction activity of the modified CIGS device under PEC conditions, linear sweep voltammetry (LSV) experiments were performed under chopped AM 1.5G illumination in a 0.1 M TBAPF 6 acetonitrile solution with 1% and 2% water as proton sources, saturated with either Ar or CO 2 (Figure a). The addition of a proton source was found to enhance the catalytic performance of the ZnO|CoPcTA NP layers, most likely by accelerating CO 2 protonation and C–O bond cleavage − along with the overall reaction CO 2 + normalH 2 normalO + 2 normale − → CO + 2 OH − …”