Suitability of Cu-substituted β-Mn2V2O7 and Mn-substituted β-Cu2V2O7 for photocatalytic water-splitting

Abstract

The pyrovanadates β-Mn 2 V 2 O7 and β-Cu 2 V 2 O7 were previously investigated as photoanode materials for water splitting. Neither of them, however, was found to be sufficiently active. In this work, we predict the properties of these two structurally similar pyrovanadates upon Cu/Mn substitution in their corresponding lattices via density functional theory calculations to explore the suitability of their band structure for water splitting and to assess their ease of synthesis. We predict that a concentration of up to 20% Cu and Mn into β-Mn 2 V 2 O7 and β-Cu 2 V 2 O7, respectively, leads to a narrowing of the bandgap, which, in the former case, is experimentally confirmed by UV-vis spectroscopy. Calculations in the intermediate composition range, however, yield nearly constant bandgaps. Moreover, we predict the materials with higher substitution levels to be increasingly difficult to synthesize, implying that low substitution levels are most relevant in terms of bandgaps and ease of synthesis.

Evaluation of Nanostructured β-Mn2V2O7 Thin Films as Photoanodes for Photoelectrochemical Water Oxidation

“…An anodic photocurrent of ∼0.1 mA cm –2 was reported for the Mn 0.5 V 0.5 O x films in 0.1 M NaOH (aq) with [Fe­(CN) 6 ] 3–/4– (a fast redox couple) when biased at ∼1.1 V versus the reversible hydrogen electrode (RHE) and illuminated with chopped ultraviolet light (3.2 eV), but no photocurrent was observed in the absence of the [Fe­(CN) 6 ] 4– hole scavenger, indicating that the samples were not appreciably photoactive for the oxygen evolution reaction (OER). The report by Yan et al generated significant interest in β-Mn 2 V 2 O 7 as a candidate water splitting material, − ,− but it also raised many questions, including whether their films were in fact β-Mn 2 V 2 O 7 and stable in base.…”

Ca2V2O7 as an Anode‐Active Material for Lithium‐Ion Batteries: Effect of Conductive Additive and Mass Loading on Electrochemical Performance

“…Following Ref [17,54,55] . the substantial decrease in capacity observed in the first cycles occurs due to the consumption of lithium ions as a result of the irreversible phase transition $${({M}_{x}{X}_{y}+{zLi}^{+}+z{e}^{-}\leftrightarrow xM+{Li}_{z}{X}_{y}}$$ ), which was previously detected in CoV 2 O 6 [17,54,55] and Mn 2 V 2 O 7 [17,21,56] . However, other authors claim that the capacity drop occurs due to SEI formation when the decomposition of the organic electrolyte is thermodynamically favorable at potentials below 1 V (versus Li/Li + ), [57] as observed in Co 2 V 2 O 7 , [18,33] Cu 2 V 2 O 7 [58] and Zn 2 (OH) 3 VO 3 [59] .…”

Cobalt-doped copper vanadate: a dual active electrocatalyst propelling efficient H2 evolution and glycerol oxidation in alkaline water

“…Despite the commendable progress in this realm, the specific influence of doped copper vanadates is mostly restricted to photoanode, supercapacitor, battery, and photocatalyst-based applications. [29][30][31][32][33] The potential of these otherwise unusual materials has been rarely probed for electrochemical reductions (cathodic) and organic molecule oxidations.…”