New study enhances hydrogen production efficiency from water

Researchers from Korea and the USA have developed highly efficient photoanodes using organometal halide perovskites (OHPs) for PEC water splitting. 

What is PEC splitting?

This method uses solar energy to split water into hydrogen and oxygen, producing zero direct emissions. 

When photons, or particles of light, strike specialized materials known as photoanodes, a cascade of events are set in motion. Water molecules respond to the incoming photons by undergoing a controlled and selective dissociation, releasing hydrogen and oxygen.

However, the broad implementation of this approach faces a constraint stemming from the scarcity of efficient photoanodes capable of catalyzing the oxygen evolution reaction (OER). The OER is a crucial step in the PEC water-splitting process, wherein water molecules are transformed into oxygen and protons.

The protons or H⁺ are the key here. They are directed to the cathode (negative electrode), where they combine with electrons from an external circuit to form hydrogen gas.

The efficiency of this reaction heavily influences the overall performance of the PEC process, making the development of efficient photoanodes a pivotal challenge in advancing the feasibility and scalability of solar-driven hydrogen production.

OHPs to the rescue

OHPs play a crucial role in boosting the efficiency of the OER in PEC water splitting. These materials excel in converting light into energy and are great for PEC photoanodes. They absorb light well and can efficiently create electron-hole pairs when exposed to sunlight.

OHPs' ability to carry charges and their catalytic power help drive the OER. OHPs can potentially produce efficient, economical PEC photoanodes, advancing sustainable hydrogen production.

However, OHPs face challenges like losses due to non-radiative recombination and slow reaction kinetics, hampering their efficiency.

To overcome this, the research team took a rational design approach.

They engineered OHP-based photoanodes by introducing layers that prevent the undesired loss of particles generated by light. Additionally, they incorporated iron or Fe-doped Ni₃S₂, a material with excellent catalytic properties, to enhance the rate at which water is converted to oxygen, reducing losses at the interface where the OHP photoanodes meet the electrolytes.

This ingenious method yielded impressive results. The Fe-doped Ni₃S₂/Ni foil/OHP photoanodes achieved an extraordinary efficiency of 12.79 percent, outperforming previous OHP-based photoanodes. This breakthrough holds the potential to transform hydrogen production methods, paving the way for more efficient and sustainable energy generation.

In a press release, Dr. Sanghan Lee, the lead author of the study from Gwangju Institute of Science and Technology, emphasized, "Our study provides insights into the rational design of high-efficiency photoanodes based on organometal halide perovskites. This technology could play a vital role in advancing the hydrogen economy and promoting sustainable energy solutions."

The study's findings are published in the journal of Advanced Energy Materials.

Study abstract:

Organometal halide perovskites (OHPs) have become potential candidates for high-efficiency photoelectrodes for use in photoelectrochemical (PEC) water splitting. However, undesired losses, such as the non-radiative recombination of photogenerated carriers and sluggish reaction kinetics of PEC water splitting, are the main limitations to achieving maximum efficiency for OHP-based photoelectrodes. Herein, high-efficiency OHP-based photoanodes with a rational design that suppresses the undesired losses is reported. As a rational design for OHP-based photoanodes, the defect-passivated electron transport layers effectively suppress the undesired recombination of photogenerated carriers from the OHP layers. In addition, Fe-doped Ni₃S₂ with a high catalytic activity promotes the reaction kinetics of PEC water oxidation, thereby suppressing the undesired losses at the interface between the OHP photoanodes and electrolytes. The fabricated Fe-doped Ni₃S₂/Ni foil/OHP photoanodes exhibit a remarkable applied bias photon-to-current efficiency of 12.79%, which is the highest of the previously reported OHP-based photoanodes by suppressing undesired losses. The strategies for achieving high-efficiency OHP-based photoanodes provide insights into the rational design of photoelectrodes based on OHPs.