Graphene-Based Modulation on the Growth of Urchin-like Na₂Ti₃O₇ Microspheres for Photothermally Enhanced H₂ Generation from Ammonia Borane

Abstract

Structural optimization and surface engineering of photocatalysts are considered as promising approaches to improve their performances effectively. The precise control of morphology and compositions during synthesis of photocatalysts is important but yet challenging. In this work, without any aid of surfactant, urchin-like reduced graphene oxide/sodium titanate (RGO/ Na 2 Ti 3 O 7 ) microspheres were fabricated by a facile, one-pot hydrothermal reaction with good reproducibility. Both microsized and nanosized graphene oxide sheets can serve as catalysts of manipulating the growth kinetics of urchin-like Na 2 Ti 3 O 7 microspheres by accelerating nucleation while inhibiting Ostwald ripening. The coupling of hierarchical Na 2 Ti 3 O 7 with RGO significantly enhanced photoelectrochemical and photocatalytic performances under visible-light irradiation. The steady-state photocurrent density of RGO/Na 2 Ti 3 O 7 -based photoanode was 13.6 times higher than those based on pristine Na 2 Ti 3 O 7 , thanks to the narrowed bandgap, enhanced light harvesting, and effective electron transfer. The surfactant-free RGO/Na 2 Ti 3 O 7 microspheres were further demonstrated as photocatalysts endowed with photothermal effect enhanced photocatalytic activity. Toward H 2 generation by hydrolysis of ammonia borane, the maximum hydrogen production rate of RGO/Na 2 Ti 3 O 7 reached 2.73 times higher than that of Na 2 Ti 3 O 7 , mainly due to the excellent photothermal efficiency up to 67.2% (higher than that of noble metal, e.g., Au dumbbell-like structure). It is believed that our understanding and reliable strategy could be extendable to construct new photocatalysts and systems toward effective solar energy harvesting and utilizations.

Fundamentals and applications of photo-thermal catalysis

“…An alternative process to generate hydrogen proposed in this current year by Dai and by Naldoni is the photo-thermally enhanced hydrolysis of ammonia borane, whose hydrogen content is 19.6%. [266][267][268] Wu et al prepared a series of urchin-like sodium titanate microspheres supported on the reduced graphene oxide (RGO/Na 2 Ti 3 O 7 ) photo-thermal catalyst with different graphene oxide content (0, 33, 50, 60, 66 wt%). 266 Particularly, they focused on the challenging aspect of synthesis optimization, elucidating the role of graphene oxide sheets in the growth mechanism of Na 2 Ti 3 O 7 microspheres.…”

“…[266][267][268] Wu et al prepared a series of urchin-like sodium titanate microspheres supported on the reduced graphene oxide (RGO/Na 2 Ti 3 O 7 ) photo-thermal catalyst with different graphene oxide content (0, 33, 50, 60, 66 wt%). 266 Particularly, they focused on the challenging aspect of synthesis optimization, elucidating the role of graphene oxide sheets in the growth mechanism of Na 2 Ti 3 O 7 microspheres. Also, they found that the photoelectrochemical performance of the prepared materials was related to the structural organization of the catalyst and the surface features of the Na 2 Ti 3 O 7 microspheres.…”

Visible-Light Acceleration of H2 Evolution from Aqueous Solutions of Inorganic Hydrides Catalyzed by Gold-Transition-Metal Nanoalloys

“…Visible-light acceleration of a number of various catalytic reactions of synthetic and environmental interest has been reported for plasmonic gold as part of heterobimetallic catalysts. 12 In particular, interest has recently focused on plasmon induced light acceleration of hydrolysis of ammonia-borane (AB), NH3BH3, by coinage metal NPs using heterobimetallic nanocatalysts either coupled to [13][14][15][16][17][18] or without a semi-conductor. [19][20][21][22][23] Inorganic hydrides such as AB and sodium borohydride, NaBH4, are promising hydrogen storage compounds, [24][25][26] because they are stable solids with high colloidal solubility in water, contain a high proportion of hydrogen and are easily transported contrary to explosive hydrogen gas.…”

Photothermal Chemistry Based on Solar Energy: From Synergistic Effects to Practical Applications

“…We have summarized a number of representative PTC works involving different fields, as shown in Table 1 . [ 33,36,38‐47,49‐57,61‐68,70‐73,75‐81,83,85,87‐89,94,111‐113,115,117,118,120,121,123‐168 ] The PTC works are categorized into three major fields, solar fuel production, chemical synthesis, and environmental remediation, and the catalysts and energy sources used in the studies, along with the reaction temperatures and reaction results are collected. Besides, the datasets of the temperatures and the reaction results have been extracted and plotted for better visibility, as shown in Figure .…”