High Throughput Discovery of Solar Fuels Photoanodes in the CuO–V₂O₅ System

Abstract

Solar photoelectrochemical generation of fuel is a promising energy technology yet the lack of an efficient, robust photoanode remains a primary materials challenge in the development and deployment of solar fuels generators. Metal oxides comprise the most promising class of photoanode materials, but no known material meets the demanding requirements of low band gap energy, photoelectrocatalysis of the oxygen evolution reaction (OER), and stability under highly oxidizing conditions. Here, the identification of new photoelectroactive materials is reported through a strategic combination of combinatorial materials synthesis, high‐throughput photoelectrochemistry, optical spectroscopy, and detailed electronic structure calculations. Four photoelectrocatalyst phases, α‐Cu2V2O7, β‐Cu2V2O7,γ‐Cu3V2O8, and Cu11V6O26, are reported with band gap energy at or below 2 eV. The photoelectrochemical properties and 30 min stability of these copper vanadate phases are demonstrated in three different aqueous electrolytes (pH 7, pH 9, and pH 13), with select combinations of phase and electrolyte exhibiting unprecedented photoelectrocatalytic stability for metal oxides with sub‐2 eV band gap. Through integration of experimental and theoretical techniques, new structure‐property relationships are determined and establish CuO–V2O5 as the most prominent composition system for OER photoelectrocatalysts, providing crucial information for materials genomes initiatives and paving the way for continued development of solar fuels photoanodes.

Solar fuels photoanode materials discovery by integrating high-throughput theory and experiment

“…3 identifies the band-character parameters as important descriptors for understanding and designing improved materials in this class. Additional characterization of the Cu-based phases discovered by this pipeline has been reported by us (32) and others (33), and we note that the collection of discoveries motivates additional studies, including (i) the exploitation of band-edge tuning to optimize energetics, (ii) the characterization of photoactivity over the full solar spectrum, and (iii) the engineering of electrochemical stability through choice of operating pH and protective or self-passivating layers, all of which are enabled by the range of vanadate chemistries identified by the pipeline. The characterization and optimization of stability is paramount to establishing a deployable photoanode, an area requiring concerted future theory and experimental effort, particularly due to the recently demonstrated propensity for ternary oxides to self-passivate under operational conditions (34).…”

Investigating cation-substituted metal vanadate photoanodes for solar water splitting

“…The bandgap reduction, if compare with BiVO4, is attributed to the lifting of valence band edge affected by the hybridization of O 2p orbitals with open-shell cation Cu 3d states. [76] These findings agree well with the hypothesis proposed in Chapter 1.…”

“…Some vanadates have been reconsidered or revealed recently as photoanode materials. [75][76][77] Manganese vanadate is originally studied as a magnetic material and later considered to be used in the lithium ion battery anode due to its good capacity and stability. [78][79][80] Manganese vanadate is normally synthesized in Mn2V2O6 and Mn2V2O7 formula with different Mn/V atomic ratio.…”

Practical challenges in the development of photoelectrochemical solar fuels production

“…Combinatorial approaches have been developed and are now in use for high through-put discovery and optimization of new semiconducting solids. 47 For the most part, present combinatorial approaches to discovery of suitable photoactive semiconductors for PEC have been directed towards metal oxide compounds 45,[47][48][49][50][51][52][53][54][55][56] Fertile ground is expected in the oxide materials, since they can be very stable and they are known to exhibit unexpected and exceptional properties, such as high Tc superconductivity, multi-ferroic phases, and exotic magnetic phenomena.…”