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Abstract:

Heterogeneous photocatalysis offers a promising route for solar-to-chemical energy conversion, yet its efficiency continues to be constrained by rapid electron-hole recombination and sluggish surface redox kinetics. Recent advances show that integrating external stimuli, such as electric, magnetic, thermal, microwave fields, can provide dynamically tuneable driving forces that influence charge, spin, and lattice behaviour in semiconductors. These external-stimuli interactions enable new mechanisms for promoting charge carrier separation, stabilising intermediates, and modulating interfacial energetics beyond the limits of conventional band-structure engineering. This review presents a comprehensive discussion of external-stimuli-assisted heterogeneous photocatalysis. We examine how different fields interact with semiconductors through various pathways. Representative material platforms, including metal oxides, polar-faceted supports, two-dimensional chalcogenides, are analysed to reveal structure-activity relationships. We further discuss emerging synergistic effects in multi-stimuli systems, where coupled fields create non-linear enhancements in photocatalytic performance. Advances in operando characterisation techniques are highlighted as essential tools for probing these dynamic processes. Together, these developments illustrate how external stimuli can be harnessed to design adaptive, field-responsive photocatalytic systems capable of significantly higher activity, selectivity, and stability. By outlining mechanistic principles, material design strategies, and key challenges, this review provides a framework for developing next-generation solar-to-chemical energy technologies.

Abstract:

We report the isolation and characterization of the first example of a crystallized high-valent Ag3+-containing polyoxometalate (POM) complex, Cs7K4[P2W19AgIIIO69(OH2)]·17H2O (1), as a “catalyst bearing catalyst” capable of catalyzing the formation of the high-valent Ni3+-containing POMs in the presence of peroxydisulfate. The oxidation state and exotic chemical behaviors of Ag in 1 were confirmed by crystallographic, spectroscopic, and electrochemical characterizations. The Ag3+/Ag+ redox pair embedded in 1 showed good electrochemical reversibility and the ability to accelerate electron transfer, contributing to the observed catalytic activity of 1 in both formation of other high-valent metal-containing POMs and electrochemical oxidative C–H activation.

Abstract:

Two-dimensional layered perovskite oxides have emerged as promising photocatalysts for solar-driven hydrogen evolution. Although doping has been widely employed to enhance photocatalytic performance, its role in modulating the electronic structure and the local chemical environment of these materials remains poorly understood. Here in this study, we investigate the codoping of Rh and La into exfoliated nanosheets of the Dion–Jacobson perovskite KCa2Nb3O10 to enhance photocatalytic hydrogen evolution reaction (HER) activity. A substantial increase in H2 evolution rate, from 12.3 to 69.0 μmol h–1, was achieved at an optimal doping level of 0.2 wt % Rh and 1.3 wt % La. Comprehensive structural and spectroscopic analyses, including synchrotron techniques and high-resolution microscopy, revealed that Rh3+ substitutes Nb5+ to introduce shallow 4d acceptor states that mediate charge separation, while La3+ substitutes Ca2+, compensates for aliovalent charge imbalance, and modulates local lattice distortions and oxygen vacancy formation. This codoping strategy enhances charge carrier lifetime and separation efficiency through a trap-mediated mechanism. The observed volcano-shaped activity trend highlights a narrow compositional window, where electronic and structural factors are optimally balanced. These findings establish a mechanistic foundation for defect engineering in layered perovskites and offer a pathway for the rational design of photocatalysts.

Abstract:

Photocatalytic ammonia decomposition offers a sustainable route for hydrogen production, but its development is limited by low catalytic efficiency and poorly understood mechanisms. Here, a protonated layered perovskite, HPrNb2O7 (HPNO), is reported as an efficient catalyst for ammonia decomposition under mild photo‐thermal conditions. Upon exposure to NH3 at elevated temperatures, HPNO promotes the in situ formation and intercalation of hydrazine intermediates within its interlayer galleries, enabled by thermally generated oxygen vacancies and hydrogen bonding. Advanced characterization techniques have been applied to confirm the formation and stabilization of hydrazine. It is also shown that thermal energy prolongs charge carrier lifetimes and enhances oxygen vacancy formation, contributing to a strong photo‐thermal synergy. The stabilization of hydrazine intermediate promotes the associative mechanism, lowering the activation barrier, thus leading to an enhanced hydrogen evolution rate of 1311.2 µmol·g−1·h−1 at 200 °C under simulated solar irradiation without any noble metal co‐catalyst. This work reveals a distinct, hydrazine‐mediated reaction pathway and positions layered protonated perovskites as promising materials for efficient, solar‐driven ammonia decomposition and sustainable hydrogen generation.

Abstract:

Despite operational mildness, hydroconversion’s reliance on fossil hydrogen raises sustainability concernsare hydrogen-free alternatives a more viable long-term strategy?