CoNiFe-LDHs decorated Ta3N5 nanotube array photoanode for remarkably enhanced photoelectrochemical glycerol conversion coupled with hydrogen generation

Solar-driven photoelectrochemical (PEC) technology has been widely recognized as a green and sustainable approach to produce fossil-fuel-alternative energy sources, whereas currently its feasibility is still a great challenge due to the lack of high-performance photoanodes. Herein, two-dimensional trimetallic CoNiFe-layered double hydroxides (CoNiFe-LDHs) nanosheets were uniformly anchored on one-dimensional Ta3N5 nanotube arrays used as a novel integrated photoanode. Serving as a hole collector, CoNiFe-LDHs can accelerate hole extraction from photo-excited Ta3N5 towards surface water oxidation reaction (WOR), thus promoting the separation of electron-hole pairs and ultimately markedly improving PEC water-splitting performance. Moreover, the trimetallic CoNiFe-LDHs were more effective in boosting the PEC performance than the three sets of bimetallic LDHs. By further replacing WOR with glycerol oxidation reaction (GOR), the composite photoanode achieved a ten-fold enhancement of solar energy conversion efficiency reaching 0.56% with nearly 100% Faradaic efficiency for concurrent generation of formate and hydrogen. Importantly, the stability of Ta3N5 was dramatically enhanced due to the synergy of CoNiFe-LDHs loading and anodic GOR. The significantly enhanced PEC properties can be mainly attributed to the increased surface active sites, promoted hole extraction and utilization, and particularly the improved charge separation efficiency. This work provides a reference for the fabrication of high-performance Ta3N5-based photoanodes towards efficient and stable PEC hydrogen generation and the green conversion of biomass derivatives into valuable chemicals.