Globally, exploring efficient utilization technologies for coal gangue, a notorious hazardous solid waste, is one of the most important issues among current sustainable development topics. Herein, a green and energy-efficient self-combustion−depolymerization (SCD) approach is proposed to activate coal gangue into highly reactive silica and alumina species for fluid catalytic cracking (FCC) catalyst synthesis. Starting from microspherical precursors composed of SCD-activated coal gangue, FCC catalysts (SCD-Y) bearing in situgenerated Y zeolites with a relative crystallinity of ca. 50% can be readily fabricated via hydrothermal synthesis. SCD-Y shows much higher catalytic activities toward heavy oil cracking than conventional catalysts. The improved performances could be ascribed to the higher accessibility of active sites and better diffusion properties of the hierarchical structure. Remarkably, compared to the conventional method, the energy consumption corresponding to material input (E m ) and the total manufacturing process (E tot ) of this SCD route falls by 46.8 and 33.5%, respectively.

Solar-driven conversion of carbon dioxide (CO 2 ) without sacrificial agents offers an attractive alternative in sustainable energy research; nevertheless, it is often retarded by the sluggish water oxidation kinetics and severe charge recombination. To this end, a Z-scheme iron oxyhydroxide/ polymeric carbon nitride (FeOOH/PCN) heterojunction, as identified by quasi in situ X-ray photoelectron spectroscopy, is constructed. In this heterostructure, the two-dimensional FeOOH nanorod provides rich coordinatively unsaturated sites and highly oxidative photoinduced holes to boost the sluggish water decomposition kinetics. Meanwhile, PCN acts as a robust agent for CO 2 reduction. Consequently, FeOOH/PCN achieves efficient CO 2 photoreduction with a superior selectivity of CH 4 (>85%), together with an apparent quantum efficiency of 2.4% at 420 nm that outperforms most two-step photosystems to date. This work offers an innovative strategy for the construction of photocatalytic systems toward solar fuel production.

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