Nickel‐molybdenum (NiMo) alloys can be a possible alternative to platinum as hydrogen evolution reaction (HER) catalysts because of the superior HER activity. However, the superior HER activity and the pH‐dependent kinetics are not currently fully understood. Herein, we present a study of HER kinetics and mechanisms of NiMo in alkaline, near‐neutral and acidic media by combining voltammetry measurements with electrochemical impedance spectroscopy and a microkinetic model. The results indicate that, compared to Ni, NiMo has significantly higher active surface area and intrinsic HER activity. In the subsequent measurements, we demonstrated that different from the existing explanations to the HER mechanisms for NiMo, the HER process in acidic, near‐neutral, and alkaline media is controlled by the Heyrovsky step. Our results show that increasing pH increases the hydrogen coverage, which increases the Tafel‐slope at low overpotentials, eventually resulting in only a single Tafel slope, which would commonly be interpreted as a Volmer‐limited reaction. Furthermore, the studies of thickness effect on HER kinetics show that the HER kinetics of NiMo are thickness‐dependent. In phosphate buffer, the increase in thickness did not significantly increase the double‐layer capacitance, but simulations with the microkinetic model indicate that the active surface area still increased similarly to other electrolytes, which is likely related to the type of electrolyte used.

Hydrogen (H₂) produced from renewables will have a growing impact on the global energy dynamics towards sustainable and carbon‐neutral standards. The share of green H₂ is still too low to meet the net‐zero target, while the demand for high‐quality hydrogen continues to rise. These factors amplify the need for economically viable H₂ generation technologies. The present article aims at evaluating the existing technologies for high‐quality H₂ production based on solar energy. Technologies such as water electrolysis, photoelectrochemical and solar thermochemical water splitting, liquid metal reactors and plasma conversion utilize solar power directly or indirectly (as carbon‐neutral electrons) and are reviewed from the perspective of their current development level, technical limitations and future potential.

With this comparative study, we present an advanced approach to the techno-economic assessment of solar-based hydrogen production.

Integrated systems for hydrogen production from photovoltaics and electrolysis could offer a solution for cost-efficient systems by omitting power electronics, but necessitate additional optimisation demand for real-world applications.

Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating a solar‐driven electrochemical hydrogen generation system with an area >10 m²with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers (ECs) using thin‐film silicon, undoped, and silver‐doped Cu(In,Ga)Se₂and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to 2600 cm²with the solar‐to‐hydrogen (StH) efficiency ranging from ≈4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC to test the effects of bifaciality (730 cm²solar collection area) and to study the long‐term operation under outdoor conditions (10 m²collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters.

Metalloid and metal based oxides are an almost unavoidable component in the majority of solar cell technologies used at the time of writing this review. Numerous studies have shown increases of ≥1% absolute in solar cell efficiency by simply substituting a given layer in the material stack with an oxide. Depending on the stoichiometry and whether other elements are present, oxides can be used for the purpose of light management, passivation of electrical defects, photo-carrier generation, charge separation, and charge transport in a solar cell. In this review, the most commonly used oxides whose benefits for solar cells have been proven both in a laboratory and industrial environment are discussed. Additionally, developing trends in the use of oxides, as well as newer oxide materials, and deposition technologies for solar cells are reported.