Urea-oxidation-assisted electrochemical water splitting for hydrogen production on a bifunctional heterostructure transition metal phosphides combining metal–organic frameworks

Unprecedented urea oxidation on Zn@Ni-MOF with an ultra-high current density: understanding the competition between UOR and OER, catalytic activity limitation and reaction selectivity

“…Also, to substitute the expensive noble metal-based state-of-the art electrocatalysts, various materials derived from earth-abundant elements have been explored for the OER and UOR. 27–40…”

“…Also, to substitute the expensive noble metal-based state-of-the art electrocatalysts, various materials derived from earth-abundant elements have been explored for the OER and UOR. [27][28][29][30][31][32][33][34][35][36][37][38][39][40] However, it is worth noting that regardless of the potential bias, the maximum UOR current density, which reects the urea oxidation rate, is oen reported to be less than 500 mA cm −2 . [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][32][33][34][35][36][37][38][39][40] This is because of the detrimental competition existing between the UOR and OER, resulting in a current tradeoff region in the anodic polarization curves.…”

“…[27][28][29][30][31][32][33][34][35][36][37][38][39][40] However, it is worth noting that regardless of the potential bias, the maximum UOR current density, which reects the urea oxidation rate, is oen reported to be less than 500 mA cm −2 . [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][32][33][34][35][36][37][38][39][40] This is because of the detrimental competition existing between the UOR and OER, resulting in a current tradeoff region in the anodic polarization curves. 17,[41][42][43][44][45] Although many works have been reported on the catalytic performance of various catalysts for easily oxidizable organic molecules including urea, hardly any work can be found in the literature regarding the fundamental understanding of the catalytic activity limitation and reaction selectivity during urea electrolysis.…”

Effective regulation on catalytic performance of nickel–iron–vanadium layered double hydroxide for urea oxidationviasulfur incorporation

“…It can be clearly observed that there is an obvious response to the oxygen evolution reaction process for the S-NiFeV LDH electrode in 1.0 M KOH solution without urea, which originates from the oxidation peak of the Ni species (Ni 2+ /Ni 3+ ). [54][55][56][57] Depicted in Fig. 5 It is evident that the elaborate S-NiFeV LDH demonstrates a significantly improved UOR performance with a low onset potential of 1.34 V (vs. RHE), beyond which a dramatic increase in current density is determined.…”

“…It can be clearly observed that there is an obvious response to the oxygen evolution reaction process for the S-NiFeV LDH electrode in 1.0 M KOH solution without urea, which originates from the oxidation peak of the Ni species (Ni 2+ /Ni 3+ ). [54][55][56][57] Depicted in Fig. 5(b) are the LSV curves of the S-NiFeV LDH, NiFeV LDH, and NiFe LDH for the UOR, along with those of the commercial RuO 2 and bare NF as a contrast.…”