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High‐efficient photoelectrocatalytic direct ammonia oxidation reaction (AOR) conducted on semiconductor photoanodes remains a substantial challenge. Herein, we develop a strategy of simply introducing ppm levels of Cu ions (0.5–10 mg/L) into NH3 solutions to significantly improve the AOR photocurrent of bare BiVO4 photoanodes from 3.4 to 6.3 mA cm−2 at 1.23 VRHE, being close to the theoretical maximum photocurrent of BiVO4 (7.5 mA cm−2). The surface charge‐separation efficiency has reached 90 % under a low bias of 0.8 VRHE. This AOR exhibits a high Faradaic efficiency (FE) of 93.8 % with the water oxidation reaction (WOR) being greatly suppressed. N2 is the main AOR product with FEs of 71.1 % in aqueous solutions and FEs of 100 % in non‐aqueous solutions. Through mechanistic studies, we find that the formation of Cu−NH3 complexes possesses preferential adsorption on BiVO4 surfaces and efficiently competes with WOR. Meanwhile, the cooperation of BiVO4 surface effect and Cu‐induced coordination effect activates N−H bonds and accelerates the first rate‐limiting proton‐coupled electron transfer for AOR. This simple strategy is further extended to other photoanodes and electrocatalysts. [ABSTRACT FROM AUTHOR]

The sluggish H2O oxidation kinetics on photoanodes severely obstructs the overall solar‐to‐energy efficiency of photoelectrochemical (PEC) cells. Herein, we find a 10 to 55‐fold increase of photocurrent by conducting ammonia oxidation reaction (AOR) on hematite (α‐Fe2O3) photoanodes under near‐neutral pH (9–11) and moderate applied potentials (1.0–1.4 VRHE) compared to H2O oxidation. By rate law analysis and operando spectroscopic studies, we confirm the non‐radical nucleophilic attack of NH3 molecules on high‐valent surface Fe−O species (e.g. FeIV=O) and Fe−N species that produces NOx− and N2, respectively, which overwhelms the nucleophilic attack of H2O on surface FeIV=O and contributes to a high Faradaic efficiency of above 80 % for AOR. This work reveals a novel non‐radical nucleophilic attack strategy, which is significantly different from the conventional indirect radical‐mediated AOR mechanism, for the rational design of high‐performance AOR photoelectrocatalysts. [ABSTRACT FROM AUTHOR]

Plasmonic photocatalysts have been emerging as a promising candidate for solar energy conversion and environmental remediation. However, those metallic plasmonic photocatalysts inevitably suffer from surface reconstruction and corrosion under harsh reaction conditions, leading to a low activity and poor chemical photostability. Herein, we observe a simultaneous improvement of both activity and photostability on Au/TiO2 nanostructure-based photoanodes induced by an in situ plasmon-mediated electrochemical activation (PMEA) treatment under photoelectrochemical (PEC) water oxidation conditions. Detailed PEC studies demonstrate that the PMEA treatment generates electron-rich surface states at Au/TiO2 interfaces, which results in a high interface charge-transfer efficiency of above 80% and boosts water oxidation activity by 100%. The electron-rich surface states further enhance the PEC stability by reducing the excessive charge accumulation at interfaces and preventing the dissolution of Au. The photoanodes are further tested for the degradation of an antibiotic, ciprofloxacin, which exhibited high PEC activity and stability. Our work provides a convenient method for improving the efficiency and chemical photostability of plasmonic photocatalysts. [ABSTRACT FROM AUTHOR]

High-efficient photoelectrocatalytic direct ammonia oxidation reaction (AOR) conducted on semiconductor photoanodes remains a substantial challenge. Herein, we develop a strategy of simply introducing ppm levels of Cu ions (0.5-10 mg/L) into NH 3 solutions to significantly improve the AOR photocurrent of bare BiVO 4 photoanodes from 3.4 to 6.3 mA cm -2 at 1.23 V RHE , being close to the theoretical maximum photocurrent of BiVO 4 (7.5 mA cm -2 ). The surface charge-separation efficiency has reached 90 % under a low bias of 0.8 V RHE . This AOR exhibits a high Faradaic efficiency (FE) of 93.8 % with the water oxidation reaction (WOR) being greatly suppressed. N 2 is the main AOR product with FEs of 71.1 % in aqueous solutions and FEs of 100 % in non-aqueous solutions. Through mechanistic studies, we find that the formation of Cu-NH 3 complexes possesses preferential adsorption on BiVO 4 surfaces and efficiently competes with WOR. Meanwhile, the cooperation of BiVO 4 surface effect and Cu-induced coordination effect activates N-H bonds and accelerates the first rate-limiting proton-coupled electron transfer for AOR. This simple strategy is further extended to other photoanodes and electrocatalysts., (© 2023 Wiley-VCH GmbH.)

Constructing heterostructures have been demonstrated as an ideal strategy for boosting charge separation on plasmonic photocatalysts, but the detailed interface charge transfer mechanism remains elusive. Herein, that authors fabricate plasmonic Au and metal-organic frameworks (MOFs, NH 2 -MIL-125 and MIL-125 used in this work) heterostructures and explore the interface charge transfer mechanism by in situ electron paramagnetic resonance (EPR) spectroscopy and electrochemical measurements. The plasmon-excited hot electrons on Au can transfer across the Au/MOF interface and be captured by the coordinatively unsaturated sites of secondary building units (Ti 8 O 8 (OH) 4 cluster) of the MOF structure, and the plasmon-excited hot holes on Au tend to transfer to and be trapped at the functionalized organic ligand (1,4-benzenedicarboxylate-NH 2 ). The spatially separated hot electrons and holes exhibit boosted the photocatalytic activity for chromium (VI) reduction and selective benzyl alcohol oxidation. This work illustrates the advantage of the versatile functionalization of MOF structures enabling molecular-level manipulation of interface charge transfer on plasmonic photocatalysts., (© 2022 Wiley-VCH GmbH.)