Abstract
The search for solar‐driven photocatalysts for overall water splitting has been actively pursued. Although metal oxynitrides with metal d0/d10‐closed shell configuration are very promising candidates in terms of their visible light absorption, they usually suffer from serious photo‐generated charge recombination and thus, little photoactivity. Here, by forming their solid solutions of LaTaON2 and CaTaO2N, which are traditionally considered to be inorganic yellow‐red pigments but have poor photocatalytic activity, a class of promising solar‐driven photocatalysts La1‐ xCaxTaO1+yN2‐ y (0 ≤ x, y ≤ 1) are explored. In particular, the optimal photocatalyst with x = 0.9 has the ability of realizing overall water splitting with stoichiometric H2/O2 ratio under the illumination of both AM1.5 simulated solar light and visible light. The modulated key parameters including band structure, Ta bonding environment, defects concentration, and band edge alignments revealed in La0.1Ca0.9TaO1+ yN2‐ y have substantially promoted the separation of photogenerated charge carriers with sufficient energetics for water oxidation and reduction reactions. The results obtained in this study provide an important candidate for designing efficient solar‐driven photocatalysts for overall water splitting.
Highlights
The search for solar-driven photocatalysts for overall water splitting has been sustainable energy infrastructure that can eventually decarbonize our fossil-fuel based actively pursued
La0.1Ca0.9TaO1+yN2-y have substantially promoted the separation of photogenerated charge carriers with sufficient energetics for water oxidation and reduction reactions
The results obtained in this study provide an important candidate for designing efficient solar-driven photocatalysts for mier target.[8]
Summary
As the key parameters including the bandgap, Ta–O/N bonding environment and defects content vary much among solid solutions, their photocatalytic activity was evaluated first by investigating two half-reactions of water splitting before optimal conditions were screened out for subsequent overall water splitting reactions. Sodium sulfite and silver nitrate aqueous solution are used as sacrificial agents to promote H2 and O2 evolution half-reactions, respectively. In both cases, La0.1Ca0.9TaO1+yN2-y (x = 0.9) shows the highest activity with striking improvements over its parent compounds. 1 wt% Pt and 3 wt% CoOx were found to be the optimal loading amount for H2 and O2 evolution half-reactions (Figure S12a,b, Supporting Information), respectively. Our attempts for overall water splitting using both Pt and CoOx loaded La0.1Ca0.9TaO1+yN2-y (x = 0.9) did not produce stoichiometric H2 and O2 This is probably due to the drawback of Pt cocatalyst that promotes back
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