Which technology is more efficient for hydrogen production, and why do you think so? What is the pros and cons for each one?
First, we have to define what is the photoelectrochemical water splitting. Water splitting is very thermodynamically and kinetically demanding process. The simplest would be to use photovoltaic cells to convert light to the electric energy and then to use water electrolysis. I would not call such combination as photoelectrochemical process. Alternatively, you use light energy to directly split water. The efficient charge separation is facilitated by applying the bias potential. Since water oxidation is more energy demanding, I believe that light should be directed to anode.
Simply, photoelectrochemical process includes: 1. light havesting (generation of photogenerated charge carriers); 2. charge carrier transport to the semiconductor/electrolyte interface; 3. charge carrier consumption by water or electrolyte. HER and OER processes occur on photocathode and photoanode, respectively. And it is widely recongnized that HER is a two-electron process, while OER is a four-electron one, sugggesting that OER is much more sluggish and requires high overpotenital. Hence, in my opinion, photocathode is more efficient. Moreover, photoanode often suffers from severe photocorrision, which is detrimental for the stability of anode. In short, it is my opinion based on my knowledge.Maybe you should find some artices for comparision.
Ali M. M. I. Qureshy
Thank you for asking a technical question. I appreciate the views of Yurii V Geletii and Xin Liu since they well explained the basic mechanism of PEC water splitting. As mentioned by Xin Liu , photoanode has some challenges such as photo corrosion as well as sluggish oxidation kinetics. In different PEC scenarios, the efficiency of photoanode and photocathode varies according to the quality of the synthesis. We need to modify the surface or bulk properties to enhance the PEC properties and in turn the HER. But in an ideal case, HER occurs at photocathode and OER at photoanodes. So finding suitable references for comparison according to your material will be useful. All the best with your research work !!
Pratik Mane "But in an ideal case, HER occurs at photocathode and OER at photoanodes." It's not necessary to illuminate both cathode and anode. The light energy is harvested on anode.
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