Solar Hydrogen

Abstract

Hydrogen is an alternative for the next generation of clean energy, especially in fuel developments with paths from high to low carbon content and low to high energy density. Hydrogen is free of carbon and when used releases no greenhouse gases or harmful substances. Hydrogen also has a gravimetric heating value (141.9 MJ kg −1 ) which is much higher than that of traditional fuels, such as petrol (47.5 MJ kg −1 ) and natural gas (55.5 MJ kg −1 ). [2] However, hydrogen production is not environmentally friendly; where over 90% originates from fossil fuels, emitting a large amount of CO 2 and pollutants. [3] Hence, "green hydrogen" processes with zero-pollution, sustainability, and high efficiency are a focus of the 21st century.In combination with solar energy, "green hydrogen" production is an opportunity. [4] A few technologies converting sunlight into hydrogen have been developed over the past century. However, low solar-to-hydrogen (STH) efficiencies restrict large-scale development. Recently, photovoltaic-electrolysis (PV-EC) and photoelectrochemical (PEC) systems have realized an STH efficiency of over 10% at laboratory scale, [5] which indicates scale-up potential. [6] Meanwhile, PEC technology has been demonstrated with numerous devices in the past half-century; such as "artificial leaf," [7] "integrated PEC," [5a] and "integrated PV-EC." [8] To develop green hydrogen further, we clarify the differences between PV-EC and PEC concepts, review the developments of both processes, summarize past studies, and estimate their potential for scale-up.In this review, we elaborate on the fundamental principles of PEC and PV-EC systematically and clarify their classifications. Then, we discuss the representative research on PV-EC and PEC chronologically, presenting the development trend. One of the essential aspects of this review is a technoeconomic analysis. Except for PV-EC, a large-scale PEC hydrogen production system (10 000 kg H 2 day −1 ) with a semi conductor-liquid junction (SLJ) is designed and analyzed. Conclusions and potential future developments for PV-EC and PEC are summarized. Note that this review is restricted to hydrogen production. The reader can refer to the literature related to the distribution, storage, and utilization of hydrogen, [9] which are essential to constructing a "hydrogen society in the future."Hydrogen, produced through a zero-pollution, sustainable, low-cost, and high-efficiency process, is regarded as the "ultimate energy" of the 21st century. Solar water-splitting techniques have immense potential to make the idea a reality. Two promising approaches, photovoltaic-electrolysis (PV-EC) and photoelectrochemistry (PEC), have demonstrated solar-to-hydrogen conversion efficiency over 10%, which is the minimum required for competitively priced, large-scale systems. Extensive studies of PV-EC and PEC devices reported within the past five decades show increasing design complexity. To accurately describe the gap between laboratory research and practical application, the basic principl...

Edge‐Sharing Octahedrally Coordinated NiFe Dual Active Sites on ZnFe2O4 for Photoelectrochemical Water Oxidation

“…Photoelectrochemical (PEC) “artificial leaf” technology, which employs photoanodes and photocathodes to store renewable solar energy in the form of chemical bonds (e.g., H 2 from water splitting) is one of the most promising energy conversion technology to realize scalable and cost‐effective solar fuel production. [ 1–3 ] In this regard, photoelectrode materials hold great importance for the conversion efficiency and the economic performance of PEC devices. Despite some well‐exploited metal oxides (e.g., Fe 2 O 3 , [ 4,5 ] BiVO 4 , [ 6,7 ] and WO 3 [ 8,9 ] ), spinel ferrites (MFe 2 O 4 , M represents divalent metal ions, such as Zn 2+ , Mg 2+ , Cu 2+ , Ni 2+ , etc.)…”

Halide perovskite photovoltaic-electrocatalysis for solar fuel generation

“…The process involves using photovoltaic cells to convert solar energy into electrical energy, which is then used to drive the electrochemical reactions for fuel production. [1][2][3] PV-EC fuel generation has gained significant interest in recent years due to its potential to provide a carbon-neutral source of renewable fuels. Using solar power to drive fuel production offers a sustainable and environmentally friendly alternative to traditional fossil fuel-based approaches.…”

Lacunary Polyoxometalate iImmobilized on Graphene Oxide: An Effective Electrocatalyst for Hydrogen Generation in Aqueous Solution

“…[1][2] Electrochemical water splitting is one of the best processes for molecular hydrogen production due to its known mechanism and facilities. [3][4][5][6] However, efficient electrocatalysts are needed to obtain remarkable current density and low overpotential in hydrogen evolution reaction (HER). [7][8][9][10] With regard to overpotential, the most effective electrocatalysts for HER are noble metals, e. g. Pt, Ru, and Pd.…”

“…Currently, molecular hydrogen has been introduced as a desired clean fuel in comparison with fossil ones specially because of its environmentally friendly properties [1–2] . Electrochemical water splitting is one of the best processes for molecular hydrogen production due to its known mechanism and facilities [3–6] . However, efficient electrocatalysts are needed to obtain remarkable current density and low overpotential in hydrogen evolution reaction (HER) [7–10] .…”