非金属B-graphene/g-C3N4异质结光催化一氧化碳还原

Photocatalytic conversion of CO to fuels with water by B-doped graphene/g-CN heterostructure

光催化一氧化碳(CO)还原是二氧化碳(CO_(2))还原合成增值化学品的关键步骤,也是高能耗费托合成(FTS)工艺的潜在替代技术之一,而高效的催化剂是该技术应用的关键.目前所报道的催化剂主要集中于金属基材料,而非金属催化剂体系的探索很少.本文利用密度泛函理论计算,设计了一种硼(B)掺杂的graphene/g-C_(3)N_(4)异质结构,用于CO的高效光催化还原.其中,sp2杂化的B形成的路易斯酸位点可以有效地捕获和活化CO分子,并在不同掺杂浓度下将CO转化为特定产物,包括CH_(3)OH,CH_(4)和C_(2)H_(5)OH.与此同时,竞争反应析氢反应(HER)能够被有效地抑制,因此反应具有高选择性.此外,非绝热动力学计算显示异质结形成的内置电场增强了光生电子和空穴的分离,从而加速了光生电子向催化位点的传输.该工作为解决FTS工艺的高能耗和低选择性难题提供了一个新思路,也为提高CO_(2)还原合成多碳产物的选择性提供了一种串联策略.

Photocatalytic reduction of carbon monoxide(CO)is a promising route to the production of high-value chemicals and fuels,as a supplement to high energy-input Fischer-Tropsch synthesis(FTS)and a key step in direct photo/electro-reduction CO_(2) to multi-carbon products.However,many current research efforts for high-efficiency FTS/CO_(2) reduction mainly focus on the metal-based catalysts,while metal-free and solar-driven photocatalysts are rarely explored.Here,by means of Lewis acid sites,a metal-free composite photocatalyst for CO reduction,namely boron(B)doped-graphene/g-C_(3)N_(4) heterostructure,is proposed.First-principles calculations show that the dopants(B)as catalytic sites can effectively capture and activate CO molecules and reduce CO to CH_(3)OH and CH_(4) in different doping content.It is worth noting that C_(2) products,i.e.,C_(2)H_(5)OH,can be produced with low free energy barriers on paradoped graphene/g-C_(3)N_(4).Meanwhile,the competitive hydrogen evolution reaction(HER)can be greatly suppressed,leading to the high selectivity of CO reduction.Moreover,the formation of a built-in electric field in heterostructure enhances the separation of photogenerated electrons and holes,which further accelerates the transmission of photogenerated electrons to the catalytic sites and improves the reaction efficiency.Overall,this work not only proposes a new strategy from a new perspective to solve problems of high energy consumption and low selectivity of FTS,but also provides a tandem strategy to solve problems of CO_(2) to multi-carbon products.