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In the present work, we prepare rolled up graphene oxide sheets (GOSs) by "evaporating" GOSs from their dispersion to a remote aluminum foil surface. The topological structure of the rolled up GOSs on the aluminum foil surface, which is determined by the quantity of the formed Al³⁺ ions from the reaction between the alumina on the aluminum foil surface and the weak acidic condensed vapor of the GOS dispersion, can be easily controlled via simply changing the H₂O content in the original GOS dispersion. Meanwhile, a GO/Nafion composite membrane for proton exchange membrane fuel cell is successfully prepared utilizing the as-obtained hole-like self-assembled structure of the rolled-up GOSs as a supporting material . The resultant composite membrane exhibits excellent proton conductivity compared to that of the recast Nafion membrane, especially under low-humidity conditions. An increase in proton conductivity by several times could be easily observed here, which is mainly attributed to the rearrangement of the microstructures of Nafion matrix to significantly facilitate the proton transport with rolled up GOSs being independently incorporated. The method reported here offers new degrees of freedom to achieve such transformations among the allotropic forms of carbon and/or develop new carbon material/polymer composite materials with excellent properties.

The conversion of CO2 into fuels and feedstock chemicals via photothermal catalysis holds promise for efficient solar energy utilization to tackle the global energy shortage and climate change. Despite recent advances, it is of emerging interest to explore promising materials with excellent photothermal properties to boost the performance of photothermal CO2 catalysis. Here, we report the discovery of MXene materials as superior photothermal supports for metal nanoparticles. As a proof-of-concept study, we demonstrate that Nb2C and Ti3C2, two typical MXene materials, can enhance the photothermal effect and thus boost the photothermal catalytic activity of Ni nanoparticles. A record CO2 conversion rate of 8.50 mol·gNi –1·h–1 is achieved for Nb2C-nanosheet-supported Ni nanoparticles under intense illumination. Our study bridges the gap between photothermal MXene materials and photothermal CO2 catalysis toward more efficient solar-to-chemical energy conversions and stimulates the interest in MXene-supported metal nanoparticles for other heterogeneous catalytic reactions, particularly driven by sunlight.

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Conversion of CO2 into fuels via solar energy would be a promising strategy to reduce CO2 emissions and produce value-added carbon compounds. However, the development of efficient light-harvesting and photocatalytic systems remains a significant challenge because of scarcity of low-cost and high-efficiency catalysts in CO2 conversion. Herein, a tunable selectivity in photothermal CO2 conversion was demonstrated over a series of Fe-based catalysts developed through a simple hydrogenation/carbonization treatment with commercial Fe3O4 as a precursor. The Fe3O4 catalyst demonstrated a full selectivity toward CO (about 100%) and 11.3 mmol g–1 h–1 activity for the photothermal catalytic conversion of CO2. More importantly, the pure-phase θ-Fe3C produced remarkably high selectivity toward hydrocarbon products (>97%) and superior activity (10.9 mmol g–1 h–1) in the photothermal conversion of CO2. Meanwhile, it is found that the selectivity toward a hydrocarbon (CH x ) can be modulated by the extent of hydrogenation/carbonization of the Fe3O4 precursor. In addition, we demonstrated the vital influence of the nonthermal effect on the enhanced catalytic performance with the Fe-based catalysts during the photothermal conversion of CO2.