Transition metal chalcogenides have been identified as low-cost and efficient electrocatalysts to promote the hydrogen evolution reaction in alkaline media. However, the identification of active sites and the underlying catalytic mechanism remain elusive. In this work, we employ operando X-ray absorption spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy to elucidate that NiS undergoes an in-situ phase transition to an intimately mixed phase of Ni₃S₂ and NiO, generating highly active synergistic dual sites at the Ni₃S₂/NiO interface. The interfacial Ni is the active site for water dissociation and OH* adsorption while the interfacial S acts as the active site for H* adsorption and H₂ evolution. Accordingly, the in-situ formation of Ni₃S₂/NiO interfaces enables NiS electrocatalysts to achieve an overpotential of only 95 ± 8 mV at a current density of 10 mA cm⁻². Our work highlighted that the chemistry of transition metal chalcogenides is highly dynamic, and a careful control of the working conditions may lead to the in-situ formation of catalytic species that boost their catalytic performance.

The global goal for decarbonization of the energy sector and the chemical industry could become a reality by a massive increase in renewable-based technologies. For this clean energy transition, the versatile green ammonia may play a key role in the future as a fossil-free fertilizer, long-term energy storage medium, chemical feedstock, and clean burning fuel for transportation and decentralized power generation. The high energy-intensive industrial ammonia production has triggered researchers to look for a step change in new synthetic approaches powered by renewable energies. This review provides a comprehensive comparison of light-mediated N₂ fixation technologies for green ammonia production, including photocatalytic, photoelectrocatalytic, PV-electrocatalytic and photothermocatalytic routes. Since these approaches are still at laboratory scale, we examine the most recent developments and discuss the open challenges for future improvements. Last, we offer a technoeconomic comparison of current and emerging ammonia production technologies, highlighting costs, barriers, recommendations, and potential opportunities for the real development of the next generation of green ammonia solutions.

Inspired by the outstanding optoelectronic properties reported for all-inorganic halide perovskite quantum dots (QDs), we have evaluated the potential of these materials towards the photocatalytic and photoelectrochemical degradation of organic compounds, taking the oxidation of 2-mercaptobenzothiazole (MBT) as a proof-of-concept. First, we determined electrochemically the energy levels of dispersions of perovskite QDs with different bandgap induced by the different ratios between halides (Br and I) and metallic cations (Pb and Sn). Then, we select CsPbBr₃ QDs to demonstrate the photocatalytic and photoelectrochemical oxidation of MBT, confirming that hole injection takes place from CsPbBr₃ QDs to MBT, resulting in the total degradation of MBT as evidenced by Electro Spray Mass Spectrometry analyses. Although the stability and toxicity of these QDs are major issues to address in the near future, the results obtained in the present study open promising perspectives for the implementation of solar-driven catalytic strategies based on these fascinating materials.

The present topical review aims to summarize the role of oxygen vacancies on four of the most studied semiconducting thin film oxides (BiVO ₄ , Fe ₂ O ₃ , TiO ₂ and WO ₃ ) as photoanodes for solar water splitting.

Unveiling the role of applied bias on the charge carrier dynamics in the WO₃/BiVO₄ junction during water oxidation.