Oxygen-tolerant proton reduction catalysis: much O₂ about nothing?

Abstract

PerspectiveThis journal is

Aerobic Conditions Enhance the Photocatalytic Stability of CdS/CdOx Quantum Dots

“…The introduction of O 2 prevents ak ey inactivation pathway of CdS (over-accumulation of metallicC da nd particlea gglomeration) and therebya ffords particles with highers tability. [8][9][10] To date, little research has considered the effect of O 2 on semiconductor-driven H 2 evolution ando nly few reports are availableo nO 2 -tolerantm olecular proton-reduction catalysis. [1] Alternatively,t his reactionc an be undertaken through the oxidation of organic species, either in the form of biomass-derived substrates,s uch as EtOH, MeOH,g lucoseo rl ignocellulose, [2][3][4] or throughs elective organic oxidation reactions to generate higher-value products.…”

Electrolyte Engineering toward Efficient Hydrogen Production Electrocatalysis with Oxygen-Crossover Regulation under Densely Buffered Near-Neutral pH Conditions

“…Therefore, the concept of oxygen-tolerant HER is of great significance. 50 Recently, some novel ways have been proposed to avoid this efficiency loss: core-shell structured materials that selectively suppress the oxygen molecule mass-transport to the reduction site 10,11,51,52 and more selective catalysts toward the HER (high HER activity and poor ORR activity). 53 Previously, we carried out an ORR study under densely-buffered conditions over a Pt electrocatalyst, showing that electrolyte properties (gas solubility, the kinematic viscosity and the diffusion coefficient) solely govern the oxygen mass-transport in the densely-buffered electrolyte solution.…”

A Poly(cobaloxime)/Carbon Nanotube Electrode: Freestanding Buckypaper with Polymer‐Enhanced H2‐Evolution Performance

“…[51] Under an N 2 atmosphere,B P-PyCo exhibits al inear H 2 evolution rate for the first 3h before slowing down and becoming almost inactive after 8h.T he Co-based TON( TON Co )r eaches amaximum of 80 mol H 2 (mol Co) À1 (Figure 3b), comparable to previously reported values for cobaloxime compounds in solution. [12,20] TOF Co for BP-PyCo reaches am aximum of 32 h À1 ( Figure S7b) and decreases quickly,t hus suggesting af airly rapid deactivation of the catalyst during CPE, most probably arising from decoordination of the cobaloxime from the labile pyridine ligand during the catalytic cycle, [52] or degradation of the catalyst.…”

“…[53] Thus,d efensive (reduction of O 2 by the electrode scaffold protecting the catalyst from exposure to O 2 )a nd offensive (the cobaloximes own reduction of O 2 without being damaged) strategies are used to build arelatively air-tolerant cathode for H 2 evolution. [51] In summary,w eh ave described the facile association of at hree-dimensional freestanding MWCNT and polymeric catalyst for H 2 evolution. Them ultifunctional poly(cobaloxime)/CNT composite enables ahigh loading of the molecular catalyst, catalyst stabilization and ap rotecting effect against O 2 damage.A saresult, the polymeric hybrid material displays ac atalytic activity four times higher and twice as long compared to its monomeric counterpart.…”

“…Thel oss in faradaic yield under air as compared to that under N 2 is due to the competing reduction of oxygen by the cobaloxime. [25,51] However,t he CNTs themselves can also reduce O 2 and therefore act as as hield protecting the catalyst against the parasitic reduction of O 2 instead of protons,e nhancing the molecular catalysts efficiency under aerobic conditions. [53] Thus,d efensive (reduction of O 2 by the electrode scaffold protecting the catalyst from exposure to O 2 )a nd offensive (the cobaloximes own reduction of O 2 without being damaged) strategies are used to build arelatively air-tolerant cathode for H 2 evolution.…”