Photocatalytic Water Splitting on Ni-Intercalated Ruddlesden−Popper Tantalate H₂La_2/3Ta₂O₇

Abstract

A series of Ruddlesden-Popper-type hydrous layered perovskites, A′ 2 ATa 2 O 7 (A′ ) H or K, A ) La 2/3 or Sr), were presented as novel catalysts for photocatalytic water splitting into H 2 and O 2 under UV irradiation. These hydrous perovskites showed higher activity than anhydrous perovskites (KTaO 3 , La 1/3 TaO 3 ) for overall splitting of water. Results of photoluminescence spectroscopy and H 2 evolution from aqueous n-butylamine solution support the hypothesis that the high activity of the hydrous perovskites results from their hydrated layered structure, where the photogenerated electrons and holes can be effectively transferred to the intercalated substrates (H 2 O and n-butylamine). Addition of Ni cocatalyst to H 2 La 2/3 Ta 2 O 7 via an ion-exchange reaction increased the activity, while Ni addition did not improve the activity of H 2 SrTa 2 O 7 . Ni K-edge EXAFS/XANES, UV-vis spectroscopy, and TEM results for Niloaded catalysts indicate that Ni 2+ ions and small NiO clusters are intercalated into the layers of H 2 La 2/3 Ta 2 O 7 , while relatively large NiO particles at the external surface of the perovskite are the main Ni species in H 2 SrTa 2 O 7 . Thus, the highly dispersed Ni(II) species at the interlayer space are shown to act as effective sites for H 2 evolution in the photocatalytic water splitting.

Investigations of Electronic Structures and Photocatalytic Activities under Visible Light Irradiation of Lead Molybdate Replaced with Chromium(VI)

“…1,2 Recently, new photocatalysts consisting of metal ions with d 0 and d 10 electron configurations have been developed for photocatalytic H 2 and O 2 evolution from water under UV irradiation, one after another. [1][2][3][4][5][6][7][8][9][10] have been also reported as photocatalysts. Especially, the GaN:ZnO photocatalyst is active for water splitting into H 2 and O 2 .…”

Undoped Layered Perovskite Oxynitride Li2LaTa2O6N for Photocatalytic CO2 Reduction with Visible Light

“…[3,4] Since most of metal oxide photocatalysts have large band gaps (> 3eV) and are hence inactive under visible light (l > 400 nm), [5] mixed-anion compounds such as oxynitrides have attracted considerable attention as potential visible-lightresponsive photocatalysts toward solar energy conversion. [6,7] While nitrogen-doping into oxides is aconventional and facile …”

“…[3,4] Since most of metal oxide photocatalysts have large band gaps (> 3eV) and are hence inactive under visible light (l > 400 nm), [5] mixed-anion compounds such as oxynitrides have attracted considerable attention as potential visible-lightresponsive photocatalysts toward solar energy conversion. [6,7] While nitrogen-doping into oxides is aconventional and facile method to induce visible light response, [8] thec harge imbalance between oxide and nitride anions (O 2À vs.N 3À )inevitably introduces defect states,which act as recombination centers of photoexcited carriers,a nd lower photocatalytic activity as seen in nitrogen-doped TiO 2 .…”

“…[13] Adding 10 %excessofLi resulted in asingle-phaseLi 2 LaTa 2 O 6 N. Further addition of Li (20%)y ielded otherd iffraction peaksa ssignablet oL iTaO 3 . Because alkali metals pecies in oxidep recursorsu sually are pronet ov olatilizationa th ight emperatures, [4] it is likely that theuse of excess amount of Li compensatedthe loss during the high temperatureammonolysis.Unlessstated otherwise, when we hereafter addressLi 2 LaTa 2 O 6 N, it meansthe oneprepared with 10 %excessofLi.…”

Photocatalytic Water Splitting Over a Protonated Layered Perovskite Tantalate H1.81Sr0.81Bi0.19Ta2O7

“…Although much work has been done to develop new photocatalysts responsive to UV and visible light irradiation, the number of effective photocatalysts for splitting of pure water into H 2 and O 2 is still limited. Layered compounds, such as A 2 SrTa 2 O 7 Á nH 2 O (A = H, K, and Rb) [7], RbLnTa 2 O 7 (Ln = La, Pr, Nd, and Sm) [8] Sr 2 Nb 2 O 7 [9,10], KCa 2 Nb 3 O 10 [11], A 2 La 2 Ti 3 O 10 (A = K, Rb, Cs) [12][13][14], A 4 Nb 6 O 17 (A = K, Rb) [15], PbBi 2 Ta 2 O 9 [16,17], K 2 Sr 1.5 Ta 3 O 10 [18], and H 2 La 2/3 Ta 2 O 7 [19], etc., have attracted special attention in the field of water splitting into H 2 and O 2 because of the availability of the interlayer space as reaction sites, where electron-hole recombination process could be retarded by physical separation of electron and hole pairs generated by photoabsorption [20]. However, for most of the photocatalysts, it is necessary to load transition metal co-catalysts for overall water splitting.…”