Enhanced Power Generation Using a Dual-Surface-Modified Hematite Photoanode in a Direct Glyphosate Photo Fuel Cell.

Given the current and escalating global energy and environmental concerns, this work explores an innovative approach to mitigate a widely employed commercial herbicide using a direct glyphosate (Gly) photocatalytic fuel cell (PFC). The device generates power continuously by converting solar radiation, degrading and mineralizing commercial glyphosate-based fuel, and reducing sodium persulfate at the cathode. Pristine and modified hematite photoanodes were coupled to Pt/C nanoparticles dispersed in a carbon paper (CP) support (Pt/C/CP) dark cathode by using an H-type cell. The Gly/persulfate PFC shows a remarkable current and power generation enhancement after dual-surface modification of pristine hematite with segregated Hf and FeNiOx cocatalysts. The optimized photoanode elevates maximum current density (Jmax) from 0.35 to 0.71 mA cm-2 and maximum power generation (Pmax) from 0.04 to 0.065 mW cm-2, representing 102.85 and 62.50% increase in Jmax and Pmax, respectively, as compared to pristine hematite. The system demonstrated stability over a studied period of 4 h; remarkably, the photodegradation of Gly proved substantial, achieving ∼98% degradation and ∼6% mineralization. Our findings may significantly contribute to reducing Gly's environmental impact in agribusiness since it may convert the pollutant into energy at zero bias. The proposed device offers a sustainable solution to counteract Gly pollution while concurrently harnessing solar energy for power generation.

Self-Diffusion versus Intentional Doping: Beneficial and Damaging Impact on Hematite Photoanode Interfaces.

The comprehension of side effects caused by high-temperature thermal treatments in the design of (photo)electrodes is essential to achieve efficient and cost-effective devices for solar water splitting. This investigation explores the beneficial and damaging impacts of thermal treatments in the (photo)electrode design, unraveling the impact of self-diffusion and its consequences. The industrial-friendly polymeric precursor synthesis (PPS) method, which is known for its easy technological application, was chosen as the fabrication technique for hematite photoabsorbers. For substrate evaluation, two types of conductive glass substrates, aluminum borosilicate and quartz, both coated with fluorine-doped tin oxide (ABS/FTO and QTZ/FTO, respectively), were subjected to thermal treatments following the PPS protocol. Optical and structural analyses showed no significant alterations in substrate properties, whereas X-ray photoelectron spectroscopy (XPS) revealed the migration of silicon and calcium ions from the glass component to the FTO surface. This diffusion can be further mitigated by an oxide buffer layer. To track the potential ion diffusion on the photoabsorber surface and assess its effect on the photoelectrode performance, hematite was selected as the model material and deposited onto the glass substrates. From all the ions that could possibly migrate, only Si4+ and Ca2+ originating from the glass component, as well as Sn4+ from the fluorine-doped tin oxide (FTO), were detected on the surface of the hematite photoabsorber. Interestingly, the so-called "self-diffusion" of these ions did not result in any beneficial effect on the hematite photoelectrochemical response. Instead, intentional modifications showed more substantial impacts on the photoelectrochemical efficiency compared to unintentional self-diffusion. Therefore, "self-diffusion", which can unintentionally dope the hematite, is not sufficient to significantly impact the final photocurrent. These findings emphasize the importance of understanding the true effect of thermal treatments on the photoelectrode properties to unlock their full potential in photoelectrochemical applications.

Advances in Engineered Metal Oxide Thin Films by Low-Cost, Solution-Based Techniques for Green Hydrogen Production.

Functional oxide materials have become crucial in the continuous development of various fields, including those for energy applications. In this aspect, the synthesis of nanomaterials for low-cost green hydrogen production represents a huge challenge that needs to be overcome to move toward the next generation of efficient systems and devices. This perspective presents a critical assessment of hydrothermal and polymeric precursor methods as potential approaches to designing photoelectrodes for future industrial implementation. The main conditions that can affect the photoanode's physical and chemical characteristics, such as morphology, particle size, defects chemistry, dimensionality, and crystal orientation, and how they influence the photoelectrochemical performance are highlighted in this report. Strategies to tune and engineer photoelectrode and an outlook for developing efficient solar-to-hydrogen conversion using an inexpensive and stable material will also be addressed.

Challenges and prospects about the graphene role in the design of photoelectrodes for sunlight-driven water splitting.

Graphene and its derivatives have emerged as potential materials for several technological applications including sunlight-driven water splitting reactions. This review critically addresses the latest achievements concerning the use of graphene as a player in the design of hybrid-photoelectrodes for photoelectrochemical cells. Insights about the charge carrier dynamics of graphene-based photocatalysts which include metal oxides and non-metal oxide semiconductors are also discussed. The concepts underpinning the continued progress in the field of graphene/photoelectrodes, including different graphene structures, architecture as well as the possible mechanisms for hydrogen and oxygen reactions are also presented. Despite several reports having demonstrated the potential of graphene-based photocatalysts, the achieved performance remains far from the targeted benchmark efficiency for commercial application. This review also highlights the challenges and opportunities related to graphene application in photoelectrochemical cells for future directions in the field.

High-Performance Photoelectrochemical Water Oxidation with Phosphorus-Doped and Metal Phosphide Cocatalyst-Modified g-C3 N4 Formation Through Gas Treatment.

Graphitic carbon nitride (g-C3 N4 ) has been widely explored as a photocatalyst for water splitting. The anodic water oxidation reaction (WOR) remains a major obstacle for such processes, with issues such as low surface area of g-C3 N4 , poor light absorption, and low charge-transfer efficiency. In this work, such longtime concerns have been partially addressed with band gap and surface engineering of nanostructured graphitic carbon nitride (g-C3 N4 ). Specifically, surface area and charge-transfer efficiency are significantly enhanced through architecting g-C3 N4 on nanorod TiO2 to avoid aggregation of layered g-C3 N4 . Moreover, a simple phosphide gas treatment of TiO2 /g-C3 N4 configuration not only narrows the band gap of g-C3 N4 by 0.57 eV shifting it into visible range but also generates in situ a metal phosphide (M=Fe, Cu) water oxidation cocatalyst. This TiO2 /g-C3 N4 /FeP configuration significantly improves charge separation and transfer capability. As a result, our non-noble-metal photoelectrochemical system yields outstanding visible light (>420 nm) photocurrent: approximately 0.3 mA cm-2 at 1.23 V and 1.1 mA cm-2 at 2.0 V versus RHE, which is the highest for a g-C3 N4 -based photoanode. It is expected that the TiO2 /g-C3 N4 /FeP configuration synthesized by a simple phosphide gas treatment will provide new insight for producing robust g-C3 N4 for water oxidation.