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The photothermocatalytic cellulose steam reforming strategy has provided a sustainable approach, directly converting the largest renewable carbon resource (biomass), into syngas (H2 and CO) which are clean and high‐value‐added energy carriers. However, this strategy for achieving high catalytic efficiency inevitably produces char, resulting in rapid deactivation and difficult recovery of catalysts, impeding industrial application. Herein, the Ni NPs (nanoparticles) loaded on θ‐phase Al2O3 (Ni/θ‐Al2O3) catalyst enable efficient conversion of char generated during photothermocatalytic cellulose steam reforming process, thereby exhibiting high production rates of syngas (H2 3776.3 and CO 2028.1 mmol gcatalyst−1$ \rm{g}_{catalyst}^{-1} $ h−1) and excellent durability (no deactivation after 4 cycles). Compared with a reference catalyst of Ni NPs loaded on amorphous SiO2 (Ni/am‐SiO2), this study finds that the elementary step of char conversion with H2O to syngas can be enhanced on Ni/θ‐Al2O3. With an emphasis on the mechanism, a different pathway is discovered that surface hydroxyl groups participating in the formation of HCO* intermediates, further dissociating to syngas, significantly facilitate the conversion of char. Additionally, on Ni/θ‐Al2O3, the photoactivation effect enhances catalytic activity, particularly promoting the conversion of H2O with char to syngas, thus preventing deactivation caused by encapsulation of char. [ABSTRACT FROM AUTHOR]

Photothermocatalytic dry reforming of methane (DRM) offers a promising strategy for converting solar energy into fuel. However, the high light intensity required for high fuel production rates and thermodynamically more favorable coking side reactions limit this strategy. Herein, a nanocomposite of La‐doped Al2O3 supporting Ru nanoparticles (NPs) (Ru/La‐Al2O3) is synthesized. At relatively low light intensity (80.2 kW m−2), Ru/La‐Al2O3 obtains high production rates of CO and H2 per gram of Ru (rRu, CO and rRu, H2, 8410.19 and 7181.94 mmol gRu−1 min−1) with light‐to‐fuel efficiency (η, 26.6%), and completely prohibits coking. In striking contrast, the reference catalyst without La doping (Ru/Al2O3) exhibits lower rRu, CO, rRu, H2, η and produces large amounts of coke. The improved photothermocatalytic performance stems from the fact that reactive oxygen species and carbonate species are involved in the oxidation of carbon species (rate‐determining steps of DRM) through two different reaction pathways, which significantly increases catalytic activity and prevents the carbon species from polymerizing into coke. Additionally, light not only enhances the DRM on Ru NPs and the oxidation reaction between carbonate species and carbon species but also promotes the dissociation of CH4 and desorption of H2, which improves the catalytic activity and product selectivity of Ru/La‐Al2O3. [ABSTRACT FROM AUTHOR]

Photothermocatalysis provides an effective approach to sustainably produce renewable fuels by utilizing the energy of the whole solar spectrum. Here, merely with focused solar spectrum illumination, highly efficient photothermocatalytic steam cellulose reforming is achieved on Co/CeO2–Al1Mg3O4.5. The catalyst exhibits extremely high H2 and CO production rates (3374.4 and 1872.1 mmol gcatalyst−1 h−1) along with a 7.8% light-to-fuel efficiency, attributed to the light-driven thermocatalytic process on Co nanoparticles that utterly differs from traditional photocatalysis. The undesired tar mainly produced by cellulose pyrolysis is substantially reduced by the reaction of H2O with carbon-containing species. The active lattice oxygen (Olattice) of CeO2 is involved in the reaction by transferring to the surface of Co nanoparticles (Co NPs) loaded on the CeO2. The oxygen vacancies left on the surface of CeO2 nanoparticles can subsequently be replenished by oxygen from H2O dissociation, thus substantially enhancing the reaction of H2O with carbon-containing species, which is key to improving catalytic activity and reducing undesired tar yield. In addition to being the single heating source, the illumination exhibits a significant photoactivation effect on promoting the Olattice of CeO2, and surface oxygen species of Co NPs to react with the carbon-containing species, thus considerably facilitating the reaction of H2O with carbon-containing species. [ABSTRACT FROM AUTHOR]

CO2 and CH4 are greenhouse gases that can be converted into H2 and CO through light‐driven photothermocatalytic CO2 reduction with methane (CRM), which is a process of solar energy collection and storage. However, conventional catalysts require high light intensities (≥192.0 kW m−2) to obtain high fuel reaction rates and solar‐to‐fuel efficiency (η), and deactivate easily to coking at high temperature. Herein, a nanomaterial of Ni nanoparticles loaded on Ca‐doped Al2O3 (Ni/Ca–Al2O3) is synthesized. Ca doping improves the CO2 adsorption capacity of Ni/Ca–Al2O3. Under focused ultraviolet–visible–infrared illumination at low light intensity (80.8 kW m−2), Ni/Ca–Al2O3 obtains high production rates of H2 (rH2$$\left(\right. \left(\Delta\right)_{\text{c}} H^{0} _{\text{CO}} \times r_{\text{CO}} + \left(\Delta\right)_{\text{c}} H^{0} _{\text{H2}} \times r_{\text{H2}} - \left(\Delta\right)_{\text{c}} H^{0} _{\text{CH4}} \times r_{\text{CH4}} \left.\right) / P_{\text{illumination}} = \eta$$, 76.85 mmol min−1 g−1) and CO (rCO, 90.90 mmol min−1 g−1), which are 1.9 and 1.3 times of those in the dark respectively, and exhibits a large η (30.3%) and good stability. The coking rate of Ni/Ca–Al2O3 is reduced by a factor of 25.8 compared to the reference catalyst with Ni nanoparticles loaded on Al2O3. The improvement of catalytic activity and anticoking properties stems from the photoactivation, which not only accelerates the CRM on Ni nanoparticles, but also enhances the oxidation of carbon species (produced on Ni nanoparticles) through strong adsorption of CO2 on Ca–Al2O3 at Ni/Ca–Al2O3 interface. [ABSTRACT FROM AUTHOR]

The catalytic dry reforming of CH4 (DRM, CO2 + CH4 = 2H2 + 2CO) is merely driven by sunlight and has provided an effective strategy for addressing the two global issues of CO2 emission reduction and energy shortage. Challenges faced by the strategy, such as prone catalyst deactivation due to thermodynamically more favorable coking side reactions, high fuel production rate and light-to-fuel efficiency (η) being achieved only with high solar light intensity so far, need to be addressed urgently. Herein, we have synthesized a nanocomposite with Ru nanoparticles (NPs) with a high dispersion of 94.8% supported on MgO (Ru/MgO). By light-driven thermocatalytic DRM on Ru/MgO under concentrated UV-vis-IR illumination with relatively low light intensity (73.2 kW m−2), high production rates of H2 (rH2, 43.51 mmol g−1 min−1) and CO (rCO, 59.31 mmol g−1 min−1) and a large η of 19.4% have been achieved, and coking is completely prohibited. In striking contrast, a referenced catalyst of Ru NPs supported on SiO2 (Ru/SiO2) showed much lower rH2, rCO and η with obvious coking. This significantly improved light-driven thermocatalytic performance arises from the effect induced by a fence of strongly adsorbed CO2 molecules on MgO around Ru NPs at the Ru/MgO interface, which participate in the oxidation of C* species (formed by CH4 dissociation on Ru NPs) as a rate-decisive step of DRM, thus significantly enhancing catalytic activity and prohibiting C* species being polymerized to coke. The CO2 molecular fencing effect is dramatically promoted by novel photoactivation in which light not only facilitates DRM on Ru NPs but also dramatically facilitates the oxidation of C* species (formed on Ru NPs) by the strongly adsorbed CO2 on MgO at the Ru/MgO interface. [ABSTRACT FROM AUTHOR]

A nanocomposite of Ni nanoparticles (NPs) loaded on Ni‐doped Al2O3 (Ni/Ni‐Al2O3) is prepared. Very effective photothermocatalytic dry reforming of methane (DRM) is acquired by Ni/Ni‐Al2O3 under focused UV–vis–IR illumination with a relatively low light intensity of 80.7 kW m−2. Under focused UV–vis–IR illumination, Ni/Ni‐Al2O3 has high production rates of H2 (rH2$r_{\left(\text{H}\right)_{2}}$, 72.62 mmol g−1 min−1) and CO (rCO, 88.29 mmol g−1 min−1) as well as a large light‐to‐fuel efficiency (η) of 28.0%. Compared with a reference catalyst of Ni NPs loaded on Al2O3 (Ni/Al2O3), the photothermocatalytic activity and η of Ni/Ni‐Al2O3 are enhanced and its photothermocatalytic durability is significantly improved due to its coking rate being dramatically decreased by 42.5 times. This is attributed to a synergistic effect between Ni NPs and Ni‐Al2O3: the active oxygen of Ni‐Al2O3 participates in the oxidation of carbon species as one of decisive steps for DRM, thus not only improving the catalytic activity, but also dramatically promoting coking resistance. It is found that light not only plays a heating role, but also substantially reduces the activation energy of DRM, thus improving the catalytic activity and coking resistance due to the great acceleration of carbon oxidation upon focused illumination (photoactivation). [ABSTRACT FROM AUTHOR]

The photothermocatalytic cellulose steam reforming strategy has provided a sustainable approach, directly converting the largest renewable carbon resource (biomass), into syngas (H2 and CO) which are clean and high‐value‐added energy carriers. However, this strategy for achieving high catalytic efficiency inevitably produces char, resulting in rapid deactivation and difficult recovery of catalysts, impeding industrial application. Herein, the Ni NPs (nanoparticles) loaded on θ‐phase Al2O3 (Ni/θ‐Al2O3) catalyst enable efficient conversion of char generated during photothermocatalytic cellulose steam reforming process, thereby exhibiting high production rates of syngas (H2 3776.3 and CO 2028.1 mmol gcatalyst−1$ \rm{g}_{catalyst}^{-1} $ h−1) and excellent durability (no deactivation after 4 cycles). Compared with a reference catalyst of Ni NPs loaded on amorphous SiO2 (Ni/am‐SiO2), this study finds that the elementary step of char conversion with H2O to syngas can be enhanced on Ni/θ‐Al2O3. With an emphasis on the mechanism, a different pathway is discovered that surface hydroxyl groups participating in the formation of HCO* intermediates, further dissociating to syngas, significantly facilitate the conversion of char. Additionally, on Ni/θ‐Al2O3, the photoactivation effect enhances catalytic activity, particularly promoting the conversion of H2O with char to syngas, thus preventing deactivation caused by encapsulation of char. [ABSTRACT FROM AUTHOR]