Different Photostability of BiVO₄ in Near-pH-Neutral Electrolytes

Abstract

Photoelectrochemical water splitting is a promising route to produce hydrogen from solar energy. However, corrosion of photoelectrodes remains a fundamental challenge for their implementation. Here, we reveal different dissolution behaviors of BiVO 4 photoanode in pH-buffered borate, phosphate, and citrate (hole-scavenger) electrolytes, studied in operando employing an illuminated scanning flow cell. We demonstrate that decrease in photocurrents alone does not reflect the degradation of photoelectrodes. Changes in dissolution rates correlate to the evolution of surface chemistry and morphology. The correlative measurements on both sides of the liquid–semiconductor junction provide quantitative comparison and mechanistic insights into the degradation processes.

Considerations for the Accurate Measurement of Incident Photon to Current Efficiency in Photoelectrochemical Cells

“…This could be an avenue to investigate in further studies using smaller time steps and more systematic measurements, which should also include dependence on applied potential as well. We note that similarly prepared samples, but with 90 nm thick BiVO 4 layers, were used in a recent photocorrosion study (Zhang et al, 2020). In our case, the relative stability of the IPCE within the LED spectrum gave rise to the observed stability of the photocurrent, which only changed a few percent during the scans.…”

“…Recently, some of us undertook to measure the IPCE of BiVO 4 photoanodes under light bias. Light intensity dependence and photodegradation of BiVO 4 photoanodes under PEC operation is a well-known issue with these types of photoanodes, and has been studied by various groups of authors for more than a decade (and counting), including but not limited to references (Sayama et al, 2006;Abdi and van de Krol 2012;Toma et al, 2016;Zhang et al, 2019;Kou et al, 2020;Zhang et al, 2020). Nevertheless, the photocurrent under our white LED bias appeared to be relatively stable, decreasing ∼3% during a typical scan.…”

Recent Developments in Visible‐Light‐Absorbing Semitransparent Photoanodes for Tandem Cells Driving Solar Water Splitting

“…Furthermore, the photostability depends on the identity of the buffer species in the solution. [ 112 ] In contrast, Fe 2 O 3 and Ta 3 N 5 are usually used in alkaline solution. Because pH affects the performance of electrocatalysts, the dependence of the photocatalytic performance on pH is of great importance.…”

Oxygen Evolution Catalysts at Transition Metal Oxide Photoanodes: Their Differing Roles for Solar Water Splitting

“…Although α‐Fe 2 O 3 becomes less stable under less alkaline conditions, as is the case near the electrode during OER process, its remarkable stability is well‐known in the field, as evidenced by a study where pristine α‐Fe 2 O 3 shows no sign of degradation over 1000 h. [ 42 ] On the other hand, BiVO 4 suffers from photocorrosion due to surface hole accumulation. [ 43 ] The subsequent surface potential change at the interface can easily induce deleterious structural transformation based on its narrow stability window, as shown in its Pourbaix diagram. [ 44 ] Compared with protective coatings by conductive (e.g., TiO x ) or non‐conductive (e.g., Al 2 O 3 ) layers that merely isolate BiVO 4 surface from electrolyte, [ 45 ] passivation of BiVO 4 by efficient OECs leads to rapid dissipation of holes, thereby alleviating its photocorrosion.…”

“…[ 46 ] For the same reason, namely kinetically suppressed photocorrosion, much lower quantities of leached‐out Bi and V in hole‐scavenging electrolyte solutions are detected than in borate or phosphate solutions, using inductively coupled plasma mass spectrometry. [ 43 ] This BiVO 4 ‐OEC combination method can extend the lifetime of BiVO 4 dramatically. [ 47 ] Kim and Lee's review has comprehensively compiled major progresses on the photocurrent density and lifetime of BiVO 4 /OEC photoanodes.…”