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Electrocatalytic CO2reduction reaction (CO2RR) to produce multi-carbon products (C2+) is one of the most sustainable manners to achieve net-zero carbon emissions. Among many approaches, enriching grain boundaries (GBs) in copper (Cu) catalysts has been demonstrated to enable enhancement for C2+production. However, it still lacks effective strategies to controllably synthesize abundant GBs, rendering efficient C2+production a persistent challenge, especially at ampere-level current density. Herein, we propose a novel strategy, which can achieve unconventional grain fragmentation during thermal annealing and thus create controllable GB densities. The catalyst with the utmost GB density exhibits a peak C2+faradaic efficiency of ca.70.0 % in H-type cell and 68.2 % in flow cell; even more impressively, it delivers an ultra-high C2+current density of 0.768 A cm−2, outperforming most recently reported results. A combination of in situspectroscopies and theoretical calculations reveal that the enrichment of GBs yields more active sites for a higher *CO coverage, leading to promotion of the *CO-*CO coupling process and ultimately high C2+production performance.

Rational design of highly efficient photocatalysts for CO2conversion into carbonaceous fuels is of great significance to mitigate the global greenhouse effect and energy shortage problem. Among numerous materials studied for this purpose, the carbon nitride (g-C3N4) has been widely used in photocatalytic CO2reduction (PCR) due to its decent optical properties, low cost and environment friendliness. However, its wide use still remains a substantial challenge due to inefficiency of the active site and rapid recombination of photogenerated electrons and holes. Herein, we suggest a Z-scheme system of nitrogen vacancies g-C3N4/β-Bi2O3heterojunction photocatalyst based on self-assembly of nitrogen vacancies in g-C3N4nanosheets and β-Bi2O3micro-flowers, yielding an enhanced CO evolution rate of 30.56 μmol·g−1·h−1under the simulated solar light without any cocatalysts and sacrificial agents. Our detailed studies indicate that the promoted PCR performance originates from the stronger adsorption capability of the *COOH intermediates due to the cleavage of the C-C bond in nitrogen vacancies g-C3N4(NV-C3N4), turning the most endothermic step from the formation of *COOH intermediates to *CO. Moreover, the unique Z-scheme feature can efficiently facilitate the separation of photoelectron-hole pairs and enhance redox capability by optimizing the energy band structure. To sum up, this work provides deep insights and guidelines for rational design of highly efficient Z-scheme heterojunctions catalysts for CO2photoreduction to solar fuels.

Strain engineering involves intentionally inducing lattice distortion in materials to manipulate their electronic and geometric properties, along with the accompanying bond strength between reactants and catalysts. This approach presents an appealing pathway to optimize catalytic performance. However, it confronts challenges in achieving precise control, scalability and controllable modulation of intermediate species’ adsorption and desorption. Herein, we report a dynamic strain engineering method achieved through ultrasonic cavitation-induced high and low-pressure cycles, enabling periodically adjustable adsorption/desorption properties while bypassing complex synthesis procedures. Illustrated using ZnO and CO2piezo-reduction reaction as a demonstration, theoretical studies initially predict that adsorption of intermediates *COOH can be regulated within a specific range of strains. Under ultrasonic stimulation, ZnO catalyst with dynamic strain engineering exhibits a CO yield of ∼ 98.8 μmol·g−1·h−1, approximately 16.5 times higher than that achieved under ultraviolet light irradiation without dynamic strain engineering, despite the latter having a considerably stronger input power. Furthermore, we delve into the factors linked to dynamic strain amplitude and frequency. This dynamic strain engineering approach streamlines catalyst preparation and presents innovative possibilities for controlled manipulation of intermediate specie’s adsorption/desorption, with potential applications across a wide range of catalytic systems.