A functionalised nickel cyclam catalyst for CO₂ reduction: electrocatalysis, semiconductor surface immobilisation and light-driven electron transfer.

Gaia Neri,Alexander J Cowan,Xiaoe Li,Andrew J P White,Jason Y C Lim,Anna Reynal,Nicholas J Long,James J Walsh,James R Durrant,Calum Wilson

doi:10.1039/c4cp04871g

Abstract

The immobilisation of electrocatalysts for CO2 reduction onto light harvesting semiconductors is proposed to be an important step towards developing more efficient CO2 reduction photoelectrodes. Here, we report a low cost nickel cyclam complex covalently anchored to a metal oxide surface. Using transient spectroscopy we validate the role of surface immobilisation on enhancing the rate of photoelectron transfer. Furthermore [Ni(1,4,8,11-tetraazacyclotetradecane-6-carboxylic acid)](2+) (2) is shown to be a very active electrocatalyst in solution.

Highlights

The immobilisation of electrocatalysts for CO2 reduction onto light harvesting semiconductors is proposed to be an important step towards developing more efficient CO2 reduction photoelectrodes
The synthetic procedure for the dichloride salt of 2, a [Ni(cyclam)]2+ complex modified with a carboxylic acid group for binding to metal-oxide surfaces, is described in the Electronic supplementary information (ESI).† We identified functionalisation of the carbon backbone as an appropriate route as it is known that the presence of the quaternary N–H protons within 1 are critical in aiding CO2 binding and catalysis, with functionalisation of the amine groups leading to decreased selectivity.[27,28]
The rapid decay of the TiO2 photoelectron signal indicates that efficient electron transfer from the TiO2 to the immobilised catalyst occurs, in good agreement with our earlier electrochemical studies that demonstrated electron transfer from the conduction band of TiO2 to the NiII/I couple is thermodynamically viable (Fig. 4)

Summary

Introduction

The immobilisation of electrocatalysts for CO2 reduction onto light harvesting semiconductors is proposed to be an important step towards developing more efficient CO2 reduction photoelectrodes.

Results

Conclusion